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Stanford Research Systems SR785, Operating Manual And Programming Reference

The Stanford Research Systems SR785 is a high-performance audio analyzer designed for precision measurements. Unlock the full potential of this powerful device by downloading the free user manual, brochure, and detailed specifications from manualshive.com. Enhance your understanding of this groundbreaking product with comprehensive documentation available for instant download.

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Real Time Bandwidth and Overlap  2-27 

 

SR785 Dynamic Signal Analyzer 

 

 

 Real Time Bandwidth and Overlap     

What is Real Time Bandwidth?     

The Real Time Bandwidth is the largest frequency span whose corresponding time 
record exceeds the time it takes to compute the FFT measurement. At this span and 
narrower spans, it is possible to compute the measurement for every time record without 
skipping any input data. The spectra are computed in "real time".  

At spans larger than the real time bandwidth, the measurement computations take longer 
than a time record. The analyzer can not keep up and some input data must be ignored. 
Data is lost between time records while the computations are in progress.  

For FFT Resolutions greater than 100 lines, the SR785 can usually compute the 
measurements in both displays in less than a time record for all spans. This includes the 
real time digital filtering and heterodyning, the FFT processing, and averaging 
calculations. The real time bandwidth in this case is 102.4 kHz. Every input sample 
contributes to a time record and a measurement. 

Averaging Speed     

Real time bandwidth has a direct affect on measurement times when Averaging is On. 
Consider the averaging of full span (102.4 kHz) 400 line FFT’s. If the real time 
bandwidth is only 10 kHz (as in many analyzers), it takes 40 ms to compute the 
measurement for a 4 ms time record. This means 9 out of every 10 time records are 
ignored and only 25 full span measurements can be computed in a second. When 
averaging is on, this usually drops to 10 measurements per second. At this rate it's going 
to take a couple of minutes to do 500 averages. 

The SR785, on the other hand, can make real time measurements at full span (102.4 
kHz). This results in 256 measurements per second (on each display!). In fact, this is so 
fast, that the display can not be updated for each new measurement. The display only 
updates about 8 times a second. However, when Averaging is On, all of the 
measurements contribute to the average. The time to complete 500 averages is only a few 
seconds. (Instead of a few minutes!) 

Overlap Processing     

What about narrow spans where the time record is long compared to the processing time? 
The analyzer computes one measurement per time record and waits and does nothing 
until the next time record is complete. The update rate is one measurement per time 
record. With narrow spans, this is quite slow.  

With overlap processing, the analyzer does not wait for the next complete time record 
before computing the next measurement. Instead, it uses data from the previous time 
record as well as data from the current time record to compute the next measurement. 
This speeds up the update rate. Remember, most window functions are zero at the start 
and end of the time record. Thus, the points at the ends of the time record do not 
contribute much to the FFT. With overlap, these points are "re-used" and appear as 
middle points in other time records. This is why overlap effectively speeds up averaging 
and smoothes out window variations. 

Summary of Contents for SR785

Page 1: ...ramming Reference Model SR785 Dynamic Signal Analyzer 1290 D Reamwood Avenue Sunnyvale CA 94089 U S A Phone 408 744 9040 Fax 408 744 9049 Email info thinkSRS com www thinkSRS com Copyright 1995 1996 1998 Stanford Research Systems Inc All Rights Reserved ...

Page 2: ...defects in materials and workmanship for a period of one 1 year from the date of shipment Service For warranty service or repair this product must be returned to a Stanford Research Systems authorized service facility Contact Stanford Research Systems or an authorized representative before returning this product for repair Information in this document is subject to change without notice Copyright ...

Page 3: ...d circuit board and select the operating voltage by orienting the printed circuit board so that the desired voltage is visible when pushed firmly into its slot Rotate the fuse pull lever back into its normal position and insert the correct fuse into the fuse holder Line Fuse Verify that the correct line fuse is installed before connecting the line cord For 100V 120V use a 1 5 Amp fuse For 220V 240...

Page 4: ...ii ...

Page 5: ... Waterfall Display 1 34 Swept Sine Measurement 1 41 Saving and Recalling 1 47 User Math Functions 1 52 Limit Testing 1 56 Exceedance Statistics 1 60 Chapter 2 Analyzer Basics Measurement Groups 2 4 What is an FFT 2 6 FFT Frequency Spans 2 8 FFT Time Record 2 10 FFT Windowing 2 12 FFT Measurements 2 16 Views 2 21 FFT Averaging 2 24 Real Time Bandwidth and Overlap 2 27 Waterfall Display 2 30 Capture...

Page 6: ...7 FFT Frequency Menu 4 7 Octave Frequency Menu 4 12 Swept Sine Frequency Menu 4 15 Order Frequency Menu 4 19 Time Histogram Frequency Menu 4 23 Display Setup Menu 4 25 Display Options Menu 4 46 Marker Menu 4 50 Normal Marker Menu 4 54 Harmonic Marker Menu 4 58 Sideband Marker Menu 4 61 Band Marker Menu 4 64 Frequency Damping Marker Menu 4 66 Source Menus 4 67 Sine Source Menu 4 71 Chirp Source Men...

Page 7: ...om Menu 4 171 Recall Settings Menu 4 174 Disk Buffers Menu 4 177 Disk Upkeep Menu 4 182 Output Menu 4 184 System Menu 4 191 System Remote Menu 4 194 System Preferences Menu 4 196 System Date Time Menu 4 199 System Diagnostics Menu 4 200 Edit Macro Menu 4 203 Chapter 5 Programming Index of Commands 5 2 Alphabetical List of Commands 5 12 Introduction 5 21 Command Syntax 5 25 Frequency Commands 5 28 ...

Page 8: ...put Commands 5 97 System Commands 5 100 Front Panel Commands 5 102 Data Transfer Commands 5 107 Interface Commands 5 117 Nodal Degree of Freedom Commands 5 118 Status Reporting Commands 5 120 Status Word Definitions 5 124 Example Program 5 129 Chapter 6 File Conversion Why File Conversion 6 2 SR785 File Types 6 3 Supported External File Types 6 4 Using the File Conversion Utility 6 5 ...

Page 9: ...ing 2 72 Figure 2 5 Resistive Coupling 2 73 Figure 3 1 Front Panel 3 3 Figure 3 2 Rear Panel 3 8 Figure 3 3 Dual Display Screen 3 11 Figure 3 4 Overlay Display Screen 3 12 Figure 3 5 Vertical Scale Bar 3 13 Figure 3 6 Horizontal Scale Bar 3 14 Figure 3 7 Marker Region 3 15 Figure 3 8 Marker Position Bar 3 15 Figure 3 9 Status Indicator Panel 3 18 Figure 3 10 Front Panel Keypad 3 23 ...

Page 10: ...viii ...

Page 11: ...tered Time Record User Math Functions Time Capture Views Log Magnitude Linear Magnitude Magnitude Squared Real Part Imaginary Part Phase Unwrapped Phase Nichols Plot Nyquist Plot Displays Single Dual Upper Lower Front Back Waterfall with Skew Zoom and Pan FFT Resolution 100 200 400 or 800 FFT lines FFT Windows Hanning Blackman Harris Flattop Kaiser Uniform Force Exponential User defined Correlatio...

Page 12: ...4 Mbytes DOS formatted disk Save data setups and hardcopy Hard Copy Print to dot matrix or LaserJet InkJet printers Plot to HPGL or Postscript plotters Print Plot on line serial parallel or IEEE 488 or to disk file GIF EPS and PCX graphic formats available for disk output File Translation Native SR785 binary files can be converted to ASCII MATLAB MAT Files Universal File Format and HP SDF v3 Files...

Page 13: ...stortion 80 dB Single tone in band Intermodulation Distortion 80 dB Two tones in band each 6 02 dBfs Spurious 80 dBfs Alias Responses 80 dBfs Single tone outside of span 0 dBfs 1 Mhz Full Span FFT Noise Floor 100 dBfs typical Input grounded Input Range 30 dBV Hanning window 64 RMS averages Residual DC Response 30 dBfs FFT with Auto Cal On Amplitude Accuracy Single Channel 0 2 dB excluding windowin...

Page 14: ...ts 50 Ω receiving input source impedance Input Noise 10 nVrms Hz 160 dBVrms Hz above 200 Hz Trigger Input Modes Continuous Internal External or External TTL Internal Level adjustable to 100 of input scale Positive or Negative slope Minimum Trigger Amplitude 5 of input range External Level adjustable to 5V in 40 mV steps Positive or Negative slope Input Impedance 1 MΩ Max Input 5V Minimum Trigger A...

Page 15: ...9 Type 0 Sum of octave bands total power Source Output Amplitude Range 0 1 mVpk to 5 Vpk Amplitude Resolution 0 1 mVpk DC Offset 10 0 mV typical Output Impedance 5 Ω 100 mA peak output current Sine Amplitude Accuracy 1 of setting 0 Hz to 102 4 kHz 0 1 Vpk to 5 0 Vpk high impedance load Offset 0 V to 5 V max output 5 V ac dc Harmonics Sub Harmonics 0 1 Vpk to 5 Vpk 0 V offset and Spurious Signals 8...

Page 16: ...ional Variable output sample rate General Monitor Monochrome CRT 800H by 600V resolution Interfaces IEEE 488 RS232 and Printer interfaces standard All instrument functions can be controlled through the IEEE 488 and RS232 interfaces A PC XT keyboard input is provided for additional flexibility Hardcopy Print to dot matrix and HP LaserJet InkJet compatible printers Plot to HPGL or Postscript plotter...

Page 17: ...or these measurements In This Chapter General Installation 1 2 Caution 1 2 Line Voltage Selection 1 2 Line Fuse 1 2 Line Cord 1 2 Power Switch 1 2 Screen Brightness 1 2 Fan 1 2 Front Panel Quick Start 1 3 Hardkeys 1 3 Softkeys 1 3 Alt Keys 1 3 Knob 1 3 Help 1 4 Things To Watch Out For 1 5 Start 1 5 Live Display 1 5 Narrow Span 1 5 Low Detection Frequency 1 5 Averaging 1 5 Triggering 1 5 Scaling an...

Page 18: ... firmly into its slot Rotate the fuse pull lever back into its normal position and insert the correct fuse into the fuse holder Line Fuse Verify that the correct line fuse is installed before connecting the line cord For 100V 120V use a 1 5 Amp fuse For 220V 240V use a 3 4 Amp fuse Line Cord The SR785 has a detachable three wire power cord for connection to the power source and to a protective gro...

Page 19: ...ys The SR785 has a menu driven user interface The Menu keys each display a menu of softkeys The softkeys are at the right of the video display and have different functions depending upon the displayed menu There are three types of softkeys buttons lists and numeric values A button performs a function such as Full Span A list presents a list of choices or options in the entry field at the top of th...

Page 20: ...Signal Analyzer Help Enter the on screen help system by pressing Help Local Help on any hardkey or softkey is available simply by pressing the key Press 1 for the Help Index Press 0 to exit the help system and return to normal operation ...

Page 21: ... Hz take a very long time at least 2 cycles and maybe longer Do not set the sweep Start to a very low frequency to measure the DC response Octave measurements with a very low starting band take a long time to settle before the first measurement is valid The settling time is related to the bandwidth of the lowest octave band If the Lowest Band is less than 1 Hz the settling time can be very long Av...

Page 22: ...le the display to show the entire range of the data with Auto Scale A and Auto Scale B Local Make sure that the analyzer is not in the REMOTE state where the computer interfaces have setup the instrument and locked out the front panel Press the Local Help key to restore local control Reset If the analyzer still seems to function improperly turn the power off and turn it back on while holding down ...

Page 23: ...ect a function generator s output to the Ch1 A Input of the analyzer The input impedance of the analyzer is 1 MΩ The generator may require a terminator Many generators have either a 50 Ω or 600 Ω output impedance Use the appropriate feedthrough termination if necessary In general not using a terminator means that the output amplitude will not agree with the generator setting and the distortion may...

Page 24: ...w the entire range of the measurement Press Marker Max This moves the Marker to the maximum data point in the active display A The Marker should now be on the 1 024 kHz signal The Marker Position shown above the graph displays the frequency and amplitude of the signal 8 Use the knob to move the Marker around Take a look at some of the harmonics The knob normally adjusts the Marker Position within ...

Page 25: ...le A Adjust the graph scale and reference to display the entire range of the data This key can be used at any time 11 Let s measure some harmonics using the Marker Reference Press Marker Max Move the Marker to the fundamental peak Press Marker Ref Set the Marker Offset or Reference to the amplitude of the fundamental The Marker Position above the graph now reads relative to this offset 0 dB This i...

Page 26: ...to the peak fundamental Notice that Harmonic Markers little triangles appear on top of all of the harmonic peaks These indicate which data points are used in the harmonic calculations The harmonic calculations are displayed within the menu THD total harmonic distortion is relative to the fundamental Harmonic power is an absolute measurement of the harmonic power level This concludes this measureme...

Page 27: ...e divided by the Ch1 reference Thus Ch1 monitors the filter input source output and Ch2 measures the response of the device under test 3 Press Source Select the Source menu Press Chirp Choose Chirp output The output is an equal amplitude sine wave at each frequency bin of the FFT spectrum Press On Turn the source On Press Window Select the Window menu Press Window Adjust the FFT Window function Se...

Page 28: ...le A Adjust the scale and reference for DisplayA to show the entire range of the data 7 Press Marker Select the Marker menu Press Width Adjust the Marker Width for DisplayA Select Normal with the knob and press Enter Change to Normal Width 1 2 division Press Seeks Adjust what the Marker Seeks within the Marker Region Select Min with the knob and press Enter Seek the Minimum of the data within the ...

Page 29: ...b and press Enter Choose Frequency Response also Press View The measured data is a set of complex values which can be viewed in a number of different ways Select Phase with the knob and press Enter Choose Phase View to show the phase of the transfer function Press Auto Scale B Scale DisplayB to show the entire phase transfer function 10 Let s link the Markers together Press Active Display Make Dis...

Page 30: ...er Move the Marker with the knob Linked Markers move together Since we changed the DisplayA Marker to Linked moving the DisplayA Marker moves the DisplayB Marker If DisplayB is active moving its Marker does not move the DisplayA Marker To do this change the DisplayB Marker Type to Linked also This concludes this measurement example You should have a feeling for the basic operation of two channel m...

Page 31: ... the filter output on Channel 2 is required 3 Press Source Select the Source menu Press Noise Choose Noise output The output is random noise Press On Turn the source on Press Type Adjust the Noise Type Select White with the knob and press Enter This source is White Noise which extends over the entire 0 102 4 kHz frequency range 4 Press Auto Range Ch2 Let the analyzer automatically set the Input Ra...

Page 32: ... Span again Highlight the Span again Press Link Pressing Link toggles parameter linking off The Link indicator now shows DispA indicating that this menu box adjusts the span for DisplayA only Use the knob to adjust the Span to 3 2 kHz and press Enter Change the Span of DisplayA to 3 2 kHz The Span of DisplayB remains at 12 8 kHz The SR785 allows the two displays to have differing Spans and Start f...

Page 33: ...g the Hanning window while DisplayA is still using the BMH window So far we have unlinked measurement parameters Frequency Span Averaging and Window type affect the actual measurements within the displays Most analyzers do not allow these measurement parameters to be unlinked Display parameters such as Scaling Views Units and Marker functions are usually unlinked However linking them can be a conv...

Page 34: ...displays 12 Press Link and use the knob to move the Marker Both Markers move together when linked The Link key temporarily links the two display Markers together Press Enter Pressing any key removes the link between the Markers To permanently link the markers go to the Marker menu and change Marker to Link Press Marker Min Marker Min moves the Marker in the active display B to the graph minimum Pr...

Page 35: ...ear 0V Connect the generator output to the Ch1 A input of the analyzer The input impedance of the analyzer is 1 MΩ The generator may require a terminator Many generators have either a 50 Ω or 600 Ω output impedance Use the appropriate feedthrough termination if necessary In general not using a terminator means that the output amplitude will not agree with the generator setting 3 Press Input Select...

Page 36: ... pulse as a digital oscilloscope would 6 Press Window Select the Window menu Because the pulse is much shorter than the time record we need to use the Uniform or Force window The other window functions taper to zero at the start and end of the time record Always be aware of the effect windowing has on the time record and the FFT Press Window Select a new window type for both displays window type i...

Page 37: ...th the knob and Enter A negative delay means that the time record starts before the trigger event In this case the time record is about 4 ms long so a delay of 2ms will put the signal pulse in the center of the triggered time record The trigger delay is specified in time record bins at the current span Press Auto Scale B Note that the windowed time record in DisplayB shows the signal at the center...

Page 38: ...nts as fast as the analyzer can go If the generator is set to 256 Hz pulse rate the signal will drift slowly in the time record This is because the SR785 time records are exactly 1 256 Hz 3 90625 ms long 400 lines at full span and the analyzer is running in real time no missed data The drift in the time record is because the analyzer and the generator are using different time bases Adjust the gene...

Page 39: ...lter output to the Ch2 A Input Ch1 measures the source filter input and Ch2 measures the filter output 3 Press Display Setup Select the Display Setup menu Press Measure Group Change the Measurement Group Select Octave with the knob and press Enter Choose the Octave group Both displays are now making Octave Analysis measurements Press Source On Turn the source on Press Link Auto Scale A Auto Scale ...

Page 40: ...ted to 1 bandwidth of each filter Bands which are un settled are graphed in half intensity Settle is displayed until all bands in the display are settled Press Auto Scale A and Auto Scale B DisplayA Ch1 shows the flat source spectrum and DisplayB Ch2 shows the notch filter output 5 Press Average Select the Average menu Note that this menu is changed in Octave group Press Integration Time The Integ...

Page 41: ...esolution has lowered the highest band in the measurement Use the knob to select 20 kHz and press Enter Set the highest band to 20 kHz This is the highest allowed band for 2 channel 1 3 octave analysis Press Octave Channels We can change the number of channels which are being measured Use the knob to select 1 Channel and press Enter Choose single channel octave analysis This limits the insturment ...

Page 42: ...t menu Press Input Config Show the Input Configuration submenu Press Ch1 A Wt Filter Choose the Ch1 Input A Weighting filter Use the knob to select On and press Enter Turn the A Wt filter On The Ch1 Awt indicator at the top of the screen is highlighted The hardware A Wt filter conforms to the ANSI standard and is commonly used in sound measurements This filter attenuates high and low frequencies a...

Page 43: ...requency Press 1 0 2 4 select kHz with the knob and press Enter Enter 1 024 kHz for the Frequency Enter the value with the numeric entry keys Select the units with the knob Enter the new value with the Enter key Press On Turn the source on 4 Press Capture Select the Capture menu Press Allocate Memory The data memory is allocated between Capture Waterfall Order Track and Arbitrary Waveform storage ...

Page 44: ... captured half of the buffer is available for each channel Press Capture Length Increase the capture length Press 1 8 0 0 and Enter All of the capture allocation 900 blocks is available Each block stores 2 kPoints for a total of 1800 kPoints 6 Press Start Capture Start the capture The buffer will take 7 03 seconds to fill Since the Capture Mode is 1 Shot the capture stops once the buffer is full D...

Page 45: ... of the analog inputs The measurement now takes its input from the data stored in the Ch1 Capture buffer The signal reappears in the spectrum in DisplayA Only single channel measurements using Ch1 are allowed in this case there is no Ch2 data available Press Playback Config Enter the playback configuration submenu Press Playback Length You can choose to playback only a portion of the buffer if des...

Page 46: ...re captured Use the knob to select Ch1 Ch2 and press Enter Choose both channels The Capture Length is automatically halved to accommodate both channels in the allocated memory Press Sampling Rate We can increase the capture time by decreasing the Sampling Rate This decreases the bandwidth of the stored signal Use the knob to decrease the rate to 131 1 kHz and press Enter Choose 131 1 kHz as the Sa...

Page 47: ...cond for 7 73 seconds for a total of 62 updates during this playback Normal playback is limited to the real time limitations of the equivalent real time analog input measurement Press Playback Config Enter the Playback Configuration submenu Press Playback Speed Change the Playback Speed Use the knob to select Every Time Rec and press Enter Choose Every Time Record Since the data is stored in memor...

Page 48: ...at different spans windows averaging etc This is useful if the signal is hard to reproduce or occurs infrequently Press Start Reset At this span the capture buffer only holds 112 48 time records and takes only 14 seconds to playback every time record 12 Press Input Select the Input menu Press Playback Config Enter the playback configuration submenu Press Playback Length It is generally a good idea...

Page 49: ...Capture 1 33 SR785 Dynamic Signal Analyzer This concludes this example Capture and Playback is a way to record a signal and re analyze it over and over ...

Page 50: ...e self tests are completed 2 Connect the Source Output to the Channel 1 A Input Setup to analyze the source output 3 Press Display Setup Select the Display Setup menu Press Measure Group Change the Measurement Group Select Octave with the knob and press Enter Choose the Octave group Both displays are now making Octave Analysis measurements 4 Press Freq Select the Frequency menu Press Lowest Band C...

Page 51: ...n the output is noise for 96 ms out of every 100 ms If the measurement is externally or manually triggered the output is 96 ms every trigger with the minimum trigger period equal to 100 ms the source period 6 Press Average Select the Average menu Note that this menu is changed in Octave group Press Averaging Type Change the Averaging Type Use the knob to select Linear Time and press Enter Use Line...

Page 52: ... Choose Manual trigger We will start our measurement with a button press We could also use an external trigger Triggering on the signal itself requires the use of an external signal source Press Trigd Source Mode Change the Triggered Source Mode This determines whether the source triggers only once on the first trigger after Start Reset or on every trigger Use the knob to select One Shot and press...

Page 53: ...Save Options and press ENTER Use the knob to select Active Meas Only and press ENTER Use the knob to select One Shot and press Enter Choose One Shot to fill the waterfall buffer once and stop Press Total Count Change the number of measurements to store in the waterfall buffer Press 5 0 Enter The Total Count is linked to both displays by default Entering 50 changes the total count for both displays...

Page 54: ...arker in the Z direction time axis in the waterfall display This scrolls the display to show earlier measurement record When the keypad and knob are in the alternate mode the alternate key functions labeled below each key are in effect The waterfall records are numbered starting with 0 the most recent measurement in the back In this case we stored 50 records so the earliest record is number 49 The...

Page 55: ...Display recalls trace data to the active display Press Auto Scale B Auto Scale DisplayB to show the time history of Leq The points in a slice are numbered and displayed from 0 oldest to 49 newest Note that this differs from the waterfall display in which the newest record is numbered 0 This is because the slice is a time record with time advancing to the right and it is more natural to number it t...

Page 56: ...ewest records are added at the top of the waterfall display When the measurement is done or paused the waterfall may be drawn with either the newest Normal or Oldest at Top Since this measurement is measuring a transient decay it is better to draw the oldest record at the top and the subsequent smaller amplitude records in the front This concludes this example There are many display parameters in ...

Page 57: ...on is defined as Ch2 response over Ch1 reference Thus Ch1 monitors the filter input source output and Ch2 measures the response of the device under test Press Input Input Conifg Select the Input Configuration submenu Press Ch1 Input Range Adjust the Ch1 input range Press 2 select dBVpk with the knob and Enter Set the range to 2 dBV 3 Press Display Setup Select the Display Setup menu Press Measurem...

Page 58: ...e B Scale the two displays The top display is the filter input source output and should be fairly flat The bottom display is the filter output and show the filter notch at 1 kHz 6 Press Display Setup Select the Display Setup menu Press Measurement Change the Measurement of DisplayA active display Select Freq Resp with the knob and press Enter Choose Frequency Response filter output divided by filt...

Page 59: ...y the source sine and cosine and averaging the results over an integration time The actual integration time is always rounded up to an exact number of cycles of the source frequency This rejects signals which are at different frequencies such as noise and harmonics Long integration times improve signal to noise while increasing the measurement time The greater of the Integration Cycles and Integra...

Page 60: ...Auto Range increases the sweep time Press Input Input Conifg Select the Input Configuration submenu Press Channel select Ch2 with the knob and press Enter Select Ch2 Input Configuration Press Ch2 Coupling Change the Input Coupling for Ch2 Select AC with the knob and press Enter Choose AC coupling This eliminates the DC offset from the source and allows Auto Range on Ch2 to cover the entire allowab...

Page 61: ...Press Auto Level Ref Change the Auto Level Reference Select Channel 2 with the knob and press Enter Choose Channel 2 as the Auto Level Reference Press Ideal Ref Change the Ideal Reference level Press 1 0 select mV with the knob and press Enter Enter 10 mV Auto Level will try to maintain the Ch2 signal level at the Ideal Reference level by changing the source level at each point of the sweep The Ma...

Page 62: ...s the Max Source level of 1 V and the Ch2 signal drops to 60 dBV The spectrum of Ch1 measures the actual source level at each point and the Frequency Response is still calculated correctly 12 Press Active Display Switch back to DisplayA Frequency Response This concludes this measurement example You should have a basic understanding of Swept Sine measurements The Input Range Resolution and Source L...

Page 63: ...tire measurement range 3 Press Display Ref Copy the current measurement data into the reference graph for the active display A The reference graph is stored data which is associated with each display The reference graph is shown in half intensity We need to change the measurement data in order to see the reference graph since it is underneath the current data Press Input Input Conifg Select the In...

Page 64: ...nce graph The reference graph data is lost To save the reference graph transfer the reference graph to a trace before turning it off The trace may be saved to disk Press Auto Scale A Scale the graph appropriately again 5 Press Alt Print Screen Display to Trace is an alternate function This function saves the current data in the active display to a trace Use the knob to select Trace 3 and press Ent...

Page 65: ...r measurement parameters such as averaging and window type are also not allowed to be changed when the active display is Off Line Press Ymax Change the graph scale of DisplayB The view and scale of DisplayB can be changed of course These parameters simply change the way the stored data is graphed Press 8 0 and Enter Move the graph down Press Active Display Make DisplayA top the active display Note...

Page 66: ...splayA to disk Press File Name We need a file name Press Alt Alt lets you enter the letter characters printed below each key The number and backspace keys function normally ALT is highlighted at the top of the screen when the Alternate keys are in use Press D A T A 1 Enter Enter a file name any legal DOS file name up to 8 characters Pressing Enter terminates the entry and removes the Alt Press Dis...

Page 67: ...shown To show all files press Exp Press Disk to Display Recall the data in the file to the active display DisplayB Once again DisplayB is Off Line indicating that it is showing static data 9 Press Display Options Select the Display Options menu Press Display Make DisplayB live again Use the knob to select Live and press Enter Choose Live to return the live measurement to DisplayB This concludes th...

Page 68: ... Thus Ch1 monitors the filter input source output and Ch2 measures the response of the device under test 3 Press Source Select the Source menu Press On Turn on the source Press Chirp Choose Chirp output The output is an equal amplitude sine wave at each frequency bin of the FFT spectrum Press Window Select the Window menu Press Window Adjust the FFT Window function Select Uniform with the knob and...

Page 69: ...perands The display shows the available operands for this function Use Operands and Operations to switch the display between operands and operators Use the knob to highlight the desired box and press Enter to insert the selection into the function string at the top of the screen Use the knob to highlight FFT 2 and press Enter Choose FFT 2 as the first operand This is the FFT of Ch2 and is identica...

Page 70: ...e not required if they are at the very end of the string Press Enter Eq Enter the equation 7 Press Display Setup Select the Display Setup menu Press Measurement Change the measurement of the active display DisplayA Use the knob to select FFTUsrFn2 and press Enter Choose FFT User Function2 Press View Change the view Group delay is the derivative of the phase with respect to ω and is a real time Use...

Page 71: ...splay length This increases the resolution makes things narrower of the graph while decreasing the smoothing of noisy data Press 2 Enter Set the window to 2 This decreases the resolution makes thing wider while increasing the smoothing of noisy data This concludes this example User Functions allow you to define your own measurements starting with the basic SR785 measurements User Functions can als...

Page 72: ...asurement data which is greater than an Upper limit or less than a Lower limit cause the test to fail 1 Press System Display the System menu Press Preset Preset returns the unit to its default settings Press Enter to confirm Preset Preset requires confirmation to prevent accidental reset Wait until the self tests are completed 2 Connect the Source Output to the Channel 1 A Input Setup to analyze t...

Page 73: ...s at the endpoints Press X0 Select X0 first Press 8 0 0 0 Enter Enter a value of 8000 Hz Press Y0 Select Y0 Press 1 0 Enter Enter a value of 10 dBVpk Press X1 Select X1 Press 1 2 0 0 0 Enter Enter a value of 12000 Hz Press Y1 Select Y1 Press 1 0 Enter Enter a value of 10 dBVpk The segment should intersect the signal peak at 10 24 kHz Press Return Return to the Limit Test menu 4 Press Limit Testing...

Page 74: ... Y1 Select Y1 Press 8 0 Enter Enter a value of 80 dBVpk The segment should be above the noise floor The limit test should still pass 6 Press Segment Change the segment which we are editing The current segment is identified in the order in which they are created Press 0 Enter Select segment 0 the first one Before editing a segment make sure that you have chosen the correct one The current segment i...

Page 75: ... went back to the Limit Testing menu and tried to edit limits now the previous limit segments would be lost Each display only has a single set of limits and they are defined for a specific measurement view and units Press Measurement Change the Measurement back Use the knob to select FFT ch1 and press Enter Select FFT ch1 again 8 Press Analysis Select the Analysis menu Press Limit Test Go to the L...

Page 76: ...ires confirmation to prevent accidental reset Wait until the self tests are completed 2 Connect the Source Output to the Channel 1 A Input Setup to analyze the source output 3 Press Display Setup Select the Display Setup menu Press Measure Group Change the Measurement Group Select Octave with the knob and press Enter Choose the Octave group Both displays are now making Octave Analysis measurements...

Page 77: ...rfall buffer once and stop Press Total Count Change the number of measurements to store in the waterfall buffer Press 1 0 0 Enter Enter the Total Count for both displays 100 The Storage Interval is 100 ms A measurement snapshot is added to the waterfall buffer every Storage Interval so 100 measurements will take 10 s to complete Press Save Option The SR785 has two waterfall storage options for sav...

Page 78: ...ause the measurement Exceedance calculation requires that the active display be paused This ensures that the waterfall buffer is static and no new records will be added during the calculation Press Calculate Excd choose Trace 1 with the knob and press Enter The exceedance results are stored in a data trace The trace measurement is the same type as the waterfall measurements In this case the trace ...

Page 79: ...ess Enter Trace to Ref is an alternate function The alternate key functions are labeled below each key in this case the Link key Trace to Ref copies the data in a trace to the reference graph of the active display The reference graph is shown in half intensity In this case the reference graph is the level of each octave bin which is exceeded 99 of the time L99 This concludes this example Exceedanc...

Page 80: ...1 64 Exceedance Statistics ...

Page 81: ...er Spectrum 2 16 Time Record 2 17 Windowed Time Record 2 17 Orbit 2 18 Cross Spectrum 2 18 Frequency response 2 18 Coherence 2 19 Capture Buffer 2 19 User Function 2 20 Views 2 21 Log Magnitude 2 21 Linear Magnitude 2 21 Magnitude2 2 21 Real Part 2 21 Imaginary Part 2 21 Phase 2 21 Unwrapped Phase 2 22 Nyquist Plot 2 23 Nichols Plot 2 23 FFT Averaging 2 24 RMS Averaging 2 24 Vector Averaging 2 24 ...

Page 82: ... What is Order Analysis 2 55 Order Spectra and Order Tracking 2 55 Order Measurement Setup 2 55 Order Measurements 2 56 Linear Spectrum 2 56 Power Spectrum 2 56 Time Record 2 56 Windowed Time Record 2 56 RPM Profile 2 57 Orbit 2 57 Track 2 57 Capture 2 57 User Function 2 57 Time Histogram Measurements 2 58 Time and Histogram Measurements 2 58 Measurements in the Time Histogram Group 2 58 Histogram...

Page 83: ...85 Dynamic Signal Analyzer Curve Fitting and Synthesis 2 75 Curve Tables 2 75 Polynomial 2 75 Pole Zero 2 75 Pole Residue 2 75 Frequency Scale 2 76 Delay 2 76 Trace 2 76 Curve Fitting 2 76 Weighting 2 77 Curve Synthesis 2 77 ...

Page 84: ...eters chosen in the menus For some menus the choice of the Measurement Group determines which parameters are shown in the menu The Frequency Average and Source menus have different sets of parameters in each group For other menus part or all of the menu is unavailable in certain groups The Window Capture and Waterfall parameters do not apply to all groups Each group has its own set of available me...

Page 85: ...ompletely separate single channel analyzer with an independent set of operating parameters For instance in the Independent Channel mode display A could be configured to show a broadband measurement of channel 1 with linear averaging while display B could show a narrowband detail of the same input with exponential averaging The restriction of course is that in Independent Channel mode no two channe...

Page 86: ...nal power is measured to determine the signal strength in certain frequency bands By tuning the filters and repeating the measurements a reasonable spectrum can be obtained The FFT Analyzer An FFT spectrum analyzer works in an entirely different way The input signal is digitized at a high sampling rate Nyquist s theorem says that as long as the sampling rate is greater than twice the highest frequ...

Page 87: ...t at 380 Hz The FFT spectrum will detect this signal but place part of it in the 256 Hz bin and part in the 512 Hz bin One way to measure this signal accurately is to take a time record that is 1 380 Hz or 3 846 ms long with 1024 evenly spaced samples Then the signal would land all in one frequency bin But this would require changing the sampling rate based upon the signal which you haven t measur...

Page 88: ... take the approach of lowering the sample rate and making the same number of samples cover a longer time If we halve the sample rate this doubles the time record duration and gives us better resolution However the sample rate also determines the frequency span By halving the sample rate we also halve the frequency span At a constant number of points in the FFT we must tradeoff better resolution wi...

Page 89: ...on Time Record 100 bins Span 100 100 Span 200 bins Span 200 200 Span 400 bins Span 400 400 Span 800 bins Span 800 800 Span Starting the Span Above DC Using digital filtering alone requires that every span start at DC Frequency shifting is accomplished by heterodyning Heterodyning is the process of multiplying the incoming signal by a sine and cosine wave The resulting spectrum is shifted by the he...

Page 90: ...he span center is at 51 2 kHz the input range from 0 to 102 4 kHz is shifted to 51 2 kHz to 51 2 kHz This data is then passed through a low pass filter which cuts off at 51 2 kHz This results in a 51 2 kHz 102 4 kHz useable span centered at 51 2 kHz The output data only requires a sampling rate of 131 kHz instead of the original 262 kHz real input rate so only every other point is saved Thus the o...

Page 91: ...th edges of the span appear as high frequencies The anti aliasing filters have a steep but finite roll off at their cutoff frequencies Signals which are just outside of the span are not displayed in the FFT but appear frequency shifted and attenuated in the time record Zoomed time records are complex they have both a real and an imaginary part You can display the magnitude and phase as well as the...

Page 92: ...l falls within the filter If the filter is narrow then only frequencies near the exact bin frequency will contribute to the bin A narrow filter is called a selective window it selects a small range of frequencies around each bin However since the filter is narrow frequencies slightly off bin are attenuated and phase shifted Selective windows are useful for resolving adjacent peaks or improving sig...

Page 93: ...equency and very different in amplitude The Hanning window is most often used in noise measurements since it has the lowest noise floor The Hanning window function is w i N i 10 2 cos π for i 0 N 1 and N number of time record points Flattop The Flattop window has the best amplitude accuracy of any window The amplitude variation is only about 0 02 dB for signals between exact frequency bins However...

Page 94: ... The Force window is uniform over the beginning of the time record and sets the remainder of the time record to its average value This method minimizes sepectral artifacts caused by zeroing the remainder of the time record The force length is user specified This window is used to isolate impulsive signals such as impact excitations from noise and other oscillations later in the time record The Exp...

Page 95: ...FFT Windowing 2 15 SR785 Dynamic Signal Analyzer Remember window functions have a great deal of impact on the resulting FFT spectrum A poorly designed window can result in significant measurement errors ...

Page 96: ...to as the linear spectrum The phase of the spectrum is meaningful only if the time record is triggered with a fixed relationship to the input signal If the signal is repetitive as well the signal and trigger repeat then vector averaging can be used to reduce the noise level of the spectrum The vector averaged spectrum is still a complex quantity The precise definition of the FFT1 measurement for a...

Page 97: ...ion of the input signal The data is sampled and has a time resolution of 1 sample rate High frequency signals will appear distorted in the time record However ALL of the spectral information is preserved by the Nyquist sampling theorem as long as the value of each sample is accurate 2 Averaging does not affect the time record Averaging is performed on the FFT spectrum and not on the time data 3 Am...

Page 98: ...agnitude and phase information The phase is the relative phase at each frequency between the two channels Vector averaging can be used to eliminate signals which do not have a constant phase relationship between the two channels In this case triggering may not be required for vector averaging The magnitude is simply the product of the magnitudes of each spectrum Frequencies where signals are prese...

Page 99: ...th power in the reference or input channel 1 Ideally a coherence of 1 0 means that the corresponding frequency response is completely legitimate All of the response power came from power at the input If there is noise or other signals generated from within the device under test which is not related to the input signal it will result in a coherence of less than 1 0 Capture Buffer The capture buffer...

Page 100: ... data is sampled and has a time resolution of 1 sample rate High frequency signals will appear distorted in the time record However ALL of the spectral information up to the sampling rate 2 56 is preserved by the Nyquist theorem as long as the value of each sample is accurate Amplitude calibration is performed in the frequency domain Hence the captured time data amplitudes are not calibrated User ...

Page 101: ... is the imaginary part The Y axis of the display is linear in scaling Real Part Real Part view graphs the real part of the measurement data The Y axis of the display is linear in scaling Imaginary Part Imag Part view graphs the imaginary part of the measurement data The Y axis of the display is linear in scaling Real measurement data such as baseband time record have zero imaginary part This view ...

Page 102: ...frequency is between exact FFT frequency bins the filters cause phase errors Because these filters are very steep and selective they introduce very large phase shifts for signals not exactly on a frequency bin Use the SR785 source to generate exact bin frequencies whenever possible Unwrapped Phase Unwrapped Phase view graphs the phase of the measurement data as a continuous function without wrappi...

Page 103: ... Real measurement data such as baseband time record have zero imaginary part This view is entirely along the X axis Nichols Plot The Nichols Plot graphs complex measurement data as log magnitude along the Y axis versus unwrapped phase along the X axis The Y axis is logarithmic and the X axis is linear Adjacent frequency time points are connected by a line This view is generally meaningful only for...

Page 104: ...aging the result of multiplying a complex quantity by the complex conjugate of another complex quantity For instance the RMS averaged FFT is defined as RMSAvg FFT1 FFT1 FFT1 The precise definition of what RMS Averaging means for each measurement is given in the description of each measurement Baiscally since RMS averaging always involves averaging the square of a quantity RMS averaging reduces flu...

Page 105: ...er then the new data becomes the averaged data This is done on a frequency bin by bin basis The result is averaged data with the largest magnitudes which occurred over a number of measurements Peak Hold can compare a fixed number of measurements or run continuously Linear Weighting Linear weighting combines N Number Of Averages measurements with equal weighting in either RMS or Vector averaging Wh...

Page 106: ...eady state after approximately 5N measurements Once in steady state further changes in the average are detected only if they last for a sufficient number of measurements Make sure that the number of averages is not so large as to eliminate changes in the data which might be important ...

Page 107: ...are ignored and only 25 full span measurements can be computed in a second When averaging is on this usually drops to 10 measurements per second At this rate it s going to take a couple of minutes to do 500 averages The SR785 on the other hand can make real time measurements at full span 102 4 kHz This results in 256 measurements per second on each display In fact this is so fast that the display ...

Page 108: ...ecord increment for the measurements in progress is displayed in the Real Time indicator in the status area below the Input Ranges If the indicator shows a value greater than the requested Time Record Increment it means that the measurement cannot be made with the requested increment but is running with the smallest increment possible Factors which affect the processor s ability to run real time i...

Page 109: ... less than 100 Settle is displayed instead of the number of averages below the graph to indicate that the unsettled measurements are not being averaged Vector Averaging Be sure to select 100 Time Record Increment if you are interested in vector averaged measurement results Vector averaged results will be incorrect if anything besides 100 Time Record Increment is used because the phase of each time...

Page 110: ...rement is paused the display is redrawn with either the newest record in back normal or the oldest record in back reversed When paused every stored record which is visible in the display is shown The marker can access the data in any stored record and scroll the display through the entire waterfall buffer Waterfall display WITHOUT storage is simply a graphical display scrolling The marker is const...

Page 111: ...to waterfall memory is set by the Waterfall Skip Storage Interval This allows the waterfall memory to hold a longer time history as well as setting a variable storage rate In FFT Order and Time Histogram group for every record added to memory a skip number of measurements are not stored For example a skip of 0 stores every measurement in memory A skip of 10 stores every 11th measurement in memory ...

Page 112: ...yzer the oldest record at the top back This is reversed from how the display is scrolled while the measurement is running A single record can be saved to a trace A time slice history of a single X from all stored records can also be saved to a trace ...

Page 113: ...er data in that group that is not present in the other measurement groups After the inputs are digitized they may be filtered and downsampled before being stored in the capture buffer This allows longer capture times at lower sampling rates The capture data represents a frequency span from 0 Hz to the sampling rate 2 56 All captured data is baseband Capturing at less than the maximum sampling rate...

Page 114: ...the Input Source in any Measurement Group except Swept Sine Set the Playback Start point within the capture buffer and the Playback Length When playing back in FFT Group it is best to set the Playback Length to a multiple of the FFT time record Acquisition Time The Capture Progress indicator shows the playback progress through the buffer relative to Playback Length The capture buffer itself can be...

Page 115: ...sured AND displayed The display still updates at 8 Hz so playback takes about 32 seconds to complete If the time records are overlapped there may be more than 256 measurements to display and playback will take even longer When the measurement time records are very long narrow spans the time to process and display each measurement is much less than the real time record length Since the data is alre...

Page 116: ...e resulting in a low crest factor ratio of peak to rms This source is useful for measuring frequency responses quickly without having to make many discrete measurements using a single sine wave The Burst Chirp is a sweep over the FFT frequency span in a time less than the time record Burst Chirp is only available for FFT measurements Noise Broadband noise is useful for characterizing circuits mech...

Page 117: ...quency components do not have a constant amplitude over the time record Windowing will attenuate certain portions of the spectrum Windowing is required when using the Noise source Source Trigger The Sine Two Tone Chirp and Arbitrary sources can trigger the FFT time record to measure phase response and or vector average Select Source as the Trigger Source in the Trigger menu For Sine and Two Tone t...

Page 118: ...appear as triangles Signals which do not repeat or are completely random such as noise appear only at τ 0 The definition of Auto Correlation depends upon the what type of averaging is selected in the Average menu Averaging Auto Correlation invFFT FFTuN FFTN RMS or Peak Hold Averaging Auto Correlation invFFT FFTuN FFTN Vector Averaging On Auto Correlation invFFT FFTuN FFTN where N is Channel 1 or 2...

Page 119: ...riginal signal frequencies and thus do not yield the correct correlation A correlation window is applied to the time record of Ch1 in the computation This is because the FFT models the time domain as a single time record repeating itself over and over Computing the correlation over a τ greater than half of the time record length will result in wrap around where the correlation starts to repeat its...

Page 120: ... the contents of the capture buffer Correlation measurements can use this stored data as input data by choosing Playback as the Input Source in the Input menu User Function User Function displays the results of a user defined math function User Functions defined within the Correlation Analysis Measurement Group may include correlation measurement results Use the User Math menu to define a math fun...

Page 121: ...cally octave graphs always have a logarithmic X axis In addition to the octave bands the sound level is also measured and displayed as the last band in the display Exponential averaged sound power is calculated according to ANSI S1 4 1983 Type 0 Broadband Impulse and Peak measurements are made according to IEC 651 1979 Type 0 Band Center Frequencies Choose the number of bands per octave and the st...

Page 122: ...o that both displays use the same input Capture The capture buffer stores sequential time domain data in memory See Capture Buffer for more details The Capture measurement displays the contents of the capture buffer Octave measurements can use this stored data as input data by choosing Playback as the Input Source in the Input menu The capture buffer is often very long To graphically expand a regi...

Page 123: ... use the same input See User Math later in this section for more Octave Averaging All octave measurements are averaged There are four types of averaging Linear Time Exponential Time Equal Confidence and Peak Hold Linear Time The band filter outputs are equally weighted and averaged for an Integration Time While Linear averaging is in progress the integration time completed is shown in the Horizont...

Page 124: ...nput data not from the octave band outputs The bandwidth of Leq is DC 100kHz for 1 octave channel and DC 50kHz for 2 channels To measure Leq set the Averaging Type to Exponential and the Power Bin to L When the Averaging Type is Exponential or Linear the exponential time constant for Leq is the Integration Time Leq power is always an exponential average Standard measurements use either 125 ms Fast...

Page 125: ...and DC 50kHz for 2 channels To measure P set the Averaging Type Peak Hold In this case the Power Bin must be set to Peak The time constants for the Peak measurement are defined by the IEC standard The Integration Time and Confidence Level are ignored by the Peak calculation Peak power is always an exponential average The last bin in the measurement displays the Peak sound level The last bin is lab...

Page 126: ...ng time is required for the change to propagate through the octave filters and the measurement becomes valid again This settling time is 1 5xbandwidth for each band in the measurement The bandwidth of an octave filter is given by Bandwidth Center Frequency n n 2 1 2 1 2 1 2 where n 1 3 or 12 octave Settle is shown below the graph while settling takes place Bands which are un settled are displayed ...

Page 127: ... a large number of vector averages this proves difficult especially with large measurement spans Swept sine measurements on the other hand can optimize the measurement at each frequency point Since the source is a sine wave all of the source energy is concentrated at a single frequency eliminating the 30 dB chirp dynamic range penalty In addition if the transfer response drops to 100 dBV the input...

Page 128: ...oise floor at full span is about 100 dBV Thus the dynamic range of this measurement is roughly 70 dB pass band to noise floor Vector averaging in this case improves the dynamic range to about 80 dB The swept sine sweep measures each frequency alone thus optimizing each frequency point individually This measurement was taken using Auto Range to adjust the input range at each frequency for the best ...

Page 129: ...elated to an FFT span Also the number of points can range from 10 to 2047 Y axis scaling and X axis zooming are the same as with FFT displays Each data point is graphed at its correct frequency and amplitude and connected to adjacent points with a line The marker only moves to the actual sweep points and the Marker Position Bar shows the actual frequency of each point If the marker position is dis...

Page 130: ...measurement similar to the coherence measurement of the FFT measurement group The normalized variance is an indication of the signal to noise ratio after integration over the specified number of cycles is performed Normalized variance like coherence has a value between 0 and 1 A value of 1 indicates that all noise has been removed from the signal Values less than one indicate that there is noise r...

Page 131: ...nputs This allows the device under test to respond to the frequency change This can be especially important if the device under test has a high Q The Settle Time is also specified in both time and cycles of the source Times are converted to cycles and the larger of the two specified cycles is used The Integration and Settle Times are set within the Average menu Sweep Frequency and Auto Resolution ...

Page 132: ...se set the Slower Threshold to less than half of the feature size If the feature is narrow set the Maximum Step Size to less than half of the feature width in sweep points It is good practice to start by taking a sweep with Auto Resolution Off This ensures that the span and resolution of the sweep are correct as well as the averaging times Once these have been established turn Auto Resolution On t...

Page 133: ...eep This requires a level of 30 dBV When the sweep reaches the attenuation region the output signal will drop to 110 dBV While this is still measurable it may not be optimum With Auto Level the source can try to maintain an Ideal Reference of 1 0 V at the output of the device under test input of Channel 2 while not exceeding 1 0 V at the device input Where the gain is 30 dB the source level is 30 ...

Page 134: ... are not normalized in the individual measurements Only the ratio of Channel 2 to Channel 1 is source level independent The Source Ramp Rate is the rate at which the source level changes If Source Ramping is Off source level changes are made instantly If Source Ramping is On the source level changes are made at the ramp rate The Settle Time starts after the source reaches the new level This preven...

Page 135: ...e standard FFT except that the x axis is calibrated in orders instead of in absolute frequency Typically a measurement of the order spectrum is first performed to identify orders for further study Once we ve identified the problem orders we can move to the second type of measurement where the amplitude of a specific order or set of orders is recorded as the machine speed is changed We may want to ...

Page 136: ...easured relative to the tachometer pulse unless an external trigger is used in which case the phase is measured relative to the trigger Power Spectrum The Linear Spectrum in the order measurement group is similar to the Power Spectrum measurment in the FFT measurement group except that the x axis is calibrated in orders instead of absolute frequency The power spectrum gives the power present in ea...

Page 137: ...s not available for waterfall storage when tracking is enable Capture The capture buffer may be used as a source of data for order measurements See Capture Buffer for more details The Capture measurement displays the contents of the capture buffer Order measurements can use this stored data as input data by choosing Playback as the Input Source in the Input menu In the order analysis measurement g...

Page 138: ...stogram is being acquired the input signal is sampled at intervals given by Sampling Time and the number of samples in each histogram bin is recorded If Repeat has been selected the histogram will restart automatically after finishing The x axis unit of the histogram measurement is volts indicating the voltage corresponding to each histogram bin while the y axis unit is counts indicating how many ...

Page 139: ...re fill or playback progress through the buffer During capture fill if the capture accumulates points faster than they can be displayed some points are not shown This speeds up the display update so that it keeps up with the real time capture but allows visual aliasing to occur Once capture is complete the display is redrawn showing the envelope of all points eliminating any visual aliasing effect...

Page 140: ...veraging may not be modified Only display related parameters such as View Scaling and Marker Functions may be changed Off Line A stored Trace can also be recalled to the active display as its Reference Display In this case the Measurement Group associated with the Trace must be the same as the Measurement Group of the active display either Live or Off Line A stored Trace may be used as an operand ...

Page 141: ...ent Operators User Functions can also use the 5 stored Traces as operands In this case in order to display this User Function the Trace must contain data AND the Trace must have data stored from within the current Measurement Group For example an FFT User Function which uses Trace1 cannot be chosen as a Measurement if Trace1 is empty OR contains octave analysis data If a User Function is displayed...

Page 142: ...ions of the correlation measurements in terms of these operands Trace operands are simply the data stored in the Traces For example Traces can hold reference data used for normalization or calibration There are 5 Traces which can be stored These Traces are shared by all 3 Measurement Groups Constants are complex constants which are the same for every array point Constants such as pi are commonly u...

Page 143: ...th a real result Phase computes the phase tan 1 y x unwrapped with a real result Real simply zeroes the imaginary part Imag zeroes the real part Conj Ln Exp and Sqrt are defined as follows Conj x jy x jy Conj x jy x jy Ln x jy ln r jθ Exp x jy exp x cos y jsin y Sqrt x jy r cos θ 2 jsin θ 2 X 1 X x jy 1 x jy where r x2 y2 and θ tan 1 y x Sqrt computes all angles positive from 0 The X 1 X operator ...

Page 144: ... yields valid results for any complex operand which has a frequency x axis AWt is the A Weighting operator This filter is a software version of the input A Weight filter BWt and CWt are the software B Weighting and C Weighting operators The AWt BWt and CWt operators should only be used on operands with a frequency x axis All three filters conform to ANSI Standard S1 4 1983 User Function Limits Use...

Page 145: ...o automatically correct for signal variations Use the Auto Range Ch1 and Auto Range Ch2 keys to toggle Auto Ranging On and Off Specify either Normal or Tracking Auto Range in the Input menu When Normal Auto Ranging is On and an overload occurs the Input Range is increased so that the signal no longer overloads If the signal decreases the input range is not adjusted You must take care to ensure tha...

Page 146: ... noise sources take the square root of the sum of the squares of the individual noise figures For example a 6 kΩ source impedance has 10 nVrms Hz of noise Added to the input noise the overall noise is 102 102 1 2 or 14 nVrms Hz Input Impedance The input impedance of the SR785 is 1 MΩ If a higher input impedance is desired then the SR550 remote preamplifier must be used The SR550 has an input imped...

Page 147: ...ng filter conforms to ANSI standard S1 4 1983 A B and C Weighting functions are also available as operators in User Math functions Input Transducer Units Transducers such as accelerometers or microphones convert a physical quantity such as acceleration or pressure into a voltage at the analyzer s input By assigning Transducer Units to an input measurements based upon the transducer signal may be d...

Page 148: ...Grounded input If the source is grounded use a Floating input Do not use a Floating input with a floating source since the shield is simply a noise antenna in this case Noise pickup on the shield alone will appear as noise to the analyzer Common mode noise which appears on both the center and shield is rejected by the common mode rejection CMR of the analyzer input but noise on the shield only is ...

Page 149: ...Hz 0 16 Hz and attenuates signals at lower frequencies AC coupling should be used at frequencies above 160 mHz whenever possible At lower frequencies DC coupling is required For small signals it is common that the DC offset of the signal exceeds the amplitude of the AC signal of interest In this case the input range may be limited to accommodate the large DC offset while sacrificing signal to nois...

Page 150: ...the current This noise is called shot noise This can appear as voltage noise when current is passed through a resistor The shot noise or current noise is given by Inoise rms 2qI f 1 2 where q is the electron charge 1 6x10 19 Coulomb I is the RMS AC current or DC current depending upon the circuit and f is the bandwidth usually the FFT linewidth 1 f Noise Every 10 Ω resistor no matter what it is ma...

Page 151: ...und loop between the signal source and the analyzer Many of these noise sources can be minimized with good laboratory practice and experiment design There are several ways in which noise sources are coupled into the signal path Capacitive Coupling An AC voltage from a nearby piece of apparatus can couple to a signal path via a stray capacitance Although Cstray may be very small the coupled noise m...

Page 152: ... by placing the signal source in a metal box Inductive Coupling An AC current in a nearby piece of apparatus can couple to the signal path via a magnetic field A changing current in a nearby circuit gives rise to a changing magnetic field which induces an emf dΦB dt in the loop connecting the signal source to the analyzer This is like a transformer with the analyzer source loop as the secondary wi...

Page 153: ...sources of large ground currents from the ground bus used for small signals 4 Measure the signal relative to the source ground using two cables A B Set the Input Grounding to Float Microphonics Not all sources of noise are electrical in origin Mechanical noise can be translated into electrical noise by microphonic effects Physical changes in the signal source or cables due to vibrations for exampl...

Page 154: ... This source of noise is typically at very low frequency since the temperature generally changes slowly This effect is large on the scale of many signals 10 s of µV and can be a problem for low frequency measurements especially in the mHz range Some ways to minimize thermocouple effects are 1 Hold the temperature of the signal source or detector constant 2 Use a compensation junction i e a second ...

Page 155: ...race for comparison with measured data Polynomial In this format the curve table represents a frequency response function as the ratio of two polynomials in the complex frequency variable s Freq sp s Gain b s b s b a s a s a n n n n m m m m Re 1 1 0 1 1 0 The curve tables allow entry of both the numerator and denominator coefficients as well as the order of the numerator and denominator polynomial...

Page 156: ...is 1000 this will create a pole at 1 kHz when synthesizing the table Delay The three formats for a frequency response function discussed above cannot model a pure delay term of the form exp sT where T is the delay time Because of this and because measured frequency response data often includes delay a delay parameter is included in the curve table On synthesis the analyzer multiplies the Frequency...

Page 157: ...ion will be less than 1 Coherence weighting is not available for Off Line displays User weighting allows the user to specify the weighting function The analyzer uses whatever data is found in the real part of the specified weighting trace to determine the weighting Curve Synthesis The curve table is synthesized when the user presses the Synthesize Table 1 or Synthesize Table 2 softkeys The analyze...

Page 158: ...2 78 Curve Fitting and Synthesis SR785 Dynamic Signal Analyzer ...

Page 159: ...5 Marker Position Bar 3 15 Active Display 3 16 Reference Graphs 3 16 Menu Display 3 16 Status Indicators 3 18 Input Ranges 3 18 Overloads 3 18 Input Configurations 3 18 AWt 3 18 ArmWait Trig wait Trig Acquire 3 18 Run Pause Done 3 19 Analog Playback 3 19 Real Time 3 19 Sweep Frequency 3 20 RPM 3 20 Capture Progress 3 20 No Cap Cap Data 3 20 Link 3 20 Enter 3 21 ALT 3 21 GPIB RS232 3 21 Comm Error ...

Page 160: ...creen 3 32 Trace to Display Alt Help Local 3 33 Function Keys 3 34 Auto Scale A 3 34 Auto Scale B 3 34 Auto Range Ch1 3 34 Auto Range Ch2 3 35 Span Up 3 35 Span Down 3 35 Marker Ref 3 36 Display Ref 3 36 Marker Center 3 37 Marker Max 3 37 Marker Min 3 37 Show Setup 3 37 Macros 3 38 Keypad Macros 3 38 Choosing From Lists 3 38 Menus 3 38 ...

Page 161: ...N G space Figure Chapter 3 1 Front Panel Power Switch The power switch is located on the rear panel The SR785 is turned on by depressing the upper half of the power switch The green power LED on the front panel indicates that the unit is powered The video display may take a few seconds to warm up and become visible The brightness is adjusted using the Brighter and Dimmer buttons below the softkeys...

Page 162: ...ey will change the menu boxes which are displayed next to the soft keys Each menu presents a group of similar or related parameters and functions The CONTROL keys start and stop data acquisition toggle the active display and link parameters and functions These keys are not in a menu since they are used frequently and within any menu The FUNCTION keys perform common functions such as Auto Scale and...

Page 163: ... of choices are most easily modified with the knob Numeric entry fields may also be adjusted with the knob Disk Drive The 3 5 disk drive is used to store data and instrument settings Double sided high density disks DS HD have a capacity of 1 44M bytes and double sided double density disks DS DD have a capacity of 720k bytes The disk format is DOS compatible Use the Disk menu to format a disk or ac...

Page 164: ... the chassis by 1 MΩ 0 01 µF Float or 50 Ω Ground The shields should never exceed 4V Do not apply more than 50 V to either input If the input exceeds 57 V the input range will be set to 34 dBV to protect the input from damage and the HighV overload status is set The input range can not be changed while HighV is detected For two channel measurements such as Frequency Response Channel 2 is the respo...

Page 165: ...e g A to show the Frequency Menu Function Keys Letter shown below the Function key e g E for AutoScale A Control Keys Alt 1 through Alt 4 top row Alt 5 through Alt 8 bottom row Number Keys 0 through 9 Knob slow Left and Right arrow Knob fast Up and Down arrow Alt Escape Enter Enter or Return The keyboard should only be connected when the power is off ...

Page 166: ...gure Chapter 3 2 Rear Panel Power Entry Module The power entry module is used to fuse the AC line select the line voltage and block high frequency noise from entering or exiting the instrument The SR785 has a detachable three wire power cord for connection to the power source and to protective ground The exposed metal parts of the instrument are connected to the outlet ground to protect against el...

Page 167: ...he unit is set in the System Remote menu A GPIB plotter with HPGL compatible graphics may be connected to the IEEE 488 port In this case the SR785 will control the plotter to generate plots of the display graphs Select GPIB as the Output Destination and set the Plotter Address and Type in the Output menu Serial RS232 Connector The RS232 interface connector is configured as a DCE transmit on pin 3 ...

Page 168: ...coupled above 1 Hz Do not use either preamp to measure signals below 1 Hz The SR785 does not compensate for the gain of the preamp Both preamps operate at their highest gain Measurements made by the SR785 need to be divided by the gain of the preamp The SR550 has a gain of 10 and the SR552 has a gain of 100 Tachometer Input Attach a tachometer to the rear panel tachometer input to synchronize the ...

Page 169: ...ent measurements such as spectrum and time record different views such as magnitude and phase and so on Many instrument parameters are set independently for each display The display format is selected in the Display Options menu The display shown above is the Dual display format The Active Display key toggles between the two displays Display A is always on top Marker Position Bar When highlighted ...

Page 170: ...me The display normally shows the entire measurement span The X axis may be expanded Zoom and translated Pan to display less than the full measurement span This expansion does not change the measurement span or time it merely changes the display of the data Half Intensity Data Graph Unsettled measurement data is graphed in half intensity Once the measurement becomes settled the graph returns to fu...

Page 171: ...from a Trace or from disk Preview only occurs when Average Preview is On and indicates that the display is showing a preview time record and is waiting for accept or reject The Y Max and Y Min reference values are shown along the right edge Y Max is the top reference and Y Min is the bottom The vertical scale per division is shown between Y Max and Y Min The units and scale division are selected i...

Page 172: ...ber of Averages Settle is shown when the displayed measurement is not settled and is not added to the average Reject is shown when the Overload Reject is On and a measurement is not included in the average due to input overload For Swept Sine measurements the estimated Sweep Time is displayed instead of the Average Count This is the time to complete a sweep when no auto functions are selected no S...

Page 173: ...hen a Spot Marker Region is used the Marker is confined to a single X location Use the Marker menu to configure the Marker for each display The Marker position is shown in the Marker Position Bar above the graph Use the knob to move the marker in the active display The knob always moves the marker unless a menu softkey has been pressed and an entry field is displayed at the top of the screen To mo...

Page 174: ...isplay data using Display Ref or loaded from a data Trace with Trace to Ref Set the Marker Relative to Reference Display in the Marker menu to read the Marker Position relative to the Reference Display Press Display Ref again to turn off the Reference Display Changing the display scale does NOT rescale the Reference Display This allows the live measurement display to be offset from the Reference D...

Page 175: ...zer A softkey menu box which is shown in gray is not available in the current measurement Also the measurement softkeys for an Off Line display are shown in gray indicating that they may not be changed Each menu is described at length in Chapter 4 ...

Page 176: ...an overload occurs the outline of the overload bar remains in the indicator The overload outline indicates that the input has overloaded since the measurement was started This is important when the measurement is linearly averaged and an overload occurs during the average Pressing Start Reset restarts the measurement and erases this overload outline Whenever an input greater than 57 V is detected ...

Page 177: ...start of the next time record is exactly one time record advanced from the start of the previous time record If the increment is 25 then the next time record starts 1 4 of a time record advanced from the start of the previous time record This is sometimes referred to as 75 overlap since the two time records share 75 of a record The overlap is simply 100 minus the Time Record Increment If the displ...

Page 178: ...dicator shows how much of the capture buffer has been filled During capture playback this indicator shows the playback progress through the playback portion of the buffer This indicator replaces the Real time indicator when capture or playback is in progress No Cap Cap Data The Capture indicator shows the status of the Capture buffer No Cap indicates that the Capture buffer is empty Input playback...

Page 179: ... value Whenever the Enter indicator at the top of the screen is on Enter is required to enter the new choice or entry ALT Indicates that the ALTERNATE keypad is in use The ALTERNATE keypad uses the alphabetic legends printed below each key To enter the ALT mode press the ALT key once Pressing the keys will now enter alphabetic characters into the active entry field The 0 9 and ALT have the same fu...

Page 180: ...ride Remote in the System Remote menu allows front panel control even in the REMOTE state LOCK indicates that the front panel is locked out and no front panel keypress will return the unit to the local state No front panel adjustments may be made An interface command LOCL is required to exit the LOCK state macro Record indicates that a keypad macro is being recorded Use Macro Rec to start recordin...

Page 181: ...lso have alternate definitions printed below them Press the Alt key once to enter the ALT keypad mode The ALT screen indicator is on indicating that the alternate key definitions are in use Use the alternate keys to enter alphabetic characters and to access secondary functions The 0 9 Exp and Alt keys have the same definition in both modes Press Alt again to return to the normal keypad if necessar...

Page 182: ... format grid user units and log X axis Marker Configure the markers Source Turns on and configures the source Input Configures the signal and tachometer inputs and select the input ranges Trigger Setup the trigger Average Turn averaging on and select the averaging type User Math Define user math functions Window Select the measurement window Waterfall Setup waterfall displays and storage Capture S...

Page 183: ...nt selection in their softkey menu box Examples of parameter lists are View Window and Trigger Source To make a new selection press the softkey to highlight its menu box The list of possible choices is displayed in the entry field at the top of the screen For example to change the View press Display Setup for the menu and then View 3rd softkey The View menu box will be highlighted and the View sel...

Page 184: ...st softkey The Span menu box will be highlighted and the current Span value will be shown at the top of the screen The numeric entry keys are used to enter values directly For example to set the Span to 12 8 kHz press 1 2 8 As soon as the 1 is pressed the entry field shows the new value as it is entered The list of appropriate units is displayed as well The entry field displays the characters as t...

Page 185: ...justment must be made before any numeric entry is started Enter is not required to enter the new value Changes are effective immediately while the value is being adjusted Press Enter the same softkey another softkey or a menu key to un highlight the menu box when finished Some entry fields allow only knob adjustment or only numeric entry ...

Page 186: ...t Reset key Command STRT Pause Cont If the unit is already making measurements Pause Cont halts data acquisition The measurement is paused where it is and the displays are not updated The Run Pause indicator shows Pause when measurements are paused If the measurement is paused Pause Cont resumes the measurement where it was left off To start over press Start Reset The Run Pause indicator shows Run...

Page 187: ... storing data in the capture buffer If the Capture Mode is 1 Shot capture stops when the buffer is full Press Stop Capture to halt capture before the buffer is full If the Capture Mode is Continuous once capture is started it continues indefinitely and fills the capture buffer in a circular fashion In this case press Stop Capture to halt capture with the most recently acquired data stored in the b...

Page 188: ...y When a linked parameter is highlighted the Link indicator reads Link Parameter entry or selection modifies both displays at once To link or unlink a parameter highlight the parameter and press the Link key If the Link indicator is shown in gray then the parameter linking may not be changed If linking is available the value of the parameter for the non active display will be made equal to the val...

Page 189: ...REMOTE state no keypad or knob input is allowed To return to front panel operation press the Help Local key Alt Control Key Pressing Alt and a Control Key performs the function written below each key These functions are described below Play Macro Alt Start Reset Play Macro plays a recorded keypad macro Use the knob to select a defined macro and press Enter The Macro indicator at the top of the scr...

Page 190: ...race 1 5 with the knob and press Enter to save the Reference Display to the Trace A stored trace can be recalled to a Display or Reference Display used in a User Math Function saved to disk or copied to the Arbitrary Waveform buffer Command SVRF d i Trace to Ref Alt Link Trace to Ref copies Trace data into the active display s Reference Display Select a Trace 1 5 with the knob and press Enter to c...

Page 191: ...y is set back to Live in the Display Options menu The measurement frequency span averaging and window are recalled with the data and cannot be changed These menus are shown in gray and reflect the settings or values for the last Live measurement Parameters which pertain to the display of the data such as Scale and View may be changed in the Display Setup and Display Options menus When the Display ...

Page 192: ...time bins which are not shown do not figure in the auto scaling calculations Link Auto Scale B auto scales Display B and sets the vertical scale of Display A to match Display B Command ASCL d Auto Range Ch1 Auto Range Ch1 toggles Channel 1 Input Ranging between Manual and Auto In Manual Ranging the Input Range is set within the Input Input Config submenu In Auto Range the Input Range is adjusted a...

Page 193: ... displays by a factor of 2 This provides a way of adjusting the spans regardless of which menu is displayed The Span is adjusted with either a fixed start Center or End frequency depending upon which frequency was most recently anchored in the Frequency menu In Correlation group Span Up decreases the time window over which the correlation is computed but increases the time resolution In Octave gro...

Page 194: ...n is absolute Marker Ref has no affect if the Marker Rel Mode is not Off or Relative Link Marker Ref toggles the Marker Rel Mode of both displays Command MRON d Display Ref Display Ref toggles the Reference Display within the active display If the Reference Display is off Display Ref loads the Reference Display with the current display data The Reference Display is graphed in half intensity This a...

Page 195: ...he Marker Region For Harmonic or Sideband markers Marker Max moves the Fundamental Marker to the location of the maximum Marker Max has no affect on Band markers Link Marker Max moves the Marker to the location of the maximum within both displays Command MKMX d Marker Min Marker Min moves the Marker to the location of the minimum data value within the active display Marker Min only searches the da...

Page 196: ...rument Thus using the knob within a macro to choose a parameter is not recommended To choose a parameter from a list the numeric keys should be used instead of the knob while recording a macro The list choices are numbered 0 through 9 Press a number key to make a selection and Enter if required For example to select the Hanning window press Window Window 2 Enter since Hanning is entry number 2 If ...

Page 197: ...e menu shows the values or settings for the active display Press Active Display to toggle the active display and show the values or settings for the other display Measurement is an example of such a parameter Use Link to link a parameter to a single display or to both displays at once Help for any key or softkey is available on screen by pressing Help Local Simply press any key for help about that...

Page 198: ...ormat 4 46 X Axis 4 47 RPM Frequency 4 47 Grid 4 47 Grid Div 4 48 Nyquist Grid 4 48 Phase Suppress 4 48 d dx Window 4 49 Marker Menu 4 50 Marker 4 50 Mode 4 50 Normal Marker Menu 4 54 Seeks 4 54 Width 4 54 Rel 4 55 X Re l 4 55 Y Rel 4 56 X Rel 4 56 Marker X to 4 57 Target 4 57 Harmonic Marker Menu 4 58 Harmonics 4 58 Display 4 58 Readout Mode 4 59 THD 4 59 Harmonic Power 4 59 Sideband Marker Menu ...

Page 199: ...er Convert 4 94 Tachometer Input Submenu 4 95 Pulses per Rev 4 95 Tach Trigger Range 4 95 Tach Level 4 95 Tach Slope 4 96 Hold Off Enable 4 96 Tach Hold Off 4 96 Show Tach 4 96 Playback Submenu 4 97 Playback Start 4 97 Playback Length 4 97 Set Left Edge 4 97 Set Right Edge 4 98 Playback Mode 4 98 Playback Speed 4 98 Trigger Menu 4 100 Trigger Mode 4 100 Trigger Source 4 101 Trigger Level 4 102 Tri...

Page 200: ... Menu 4 143 Capture Channels 4 143 Capture Mode 4 143 Capture Length 4 144 Sampling Rate 4 144 Allocate Memory 4 145 Total Available 4 145 Capture Memory 4 145 Waterfall Memory 4 145 Arb Memory 4 145 Confirm Allocation 4 146 Clear Allocation 4 146 View Header 4 146 Auto Pan 4 146 Analysis Menu 4 147 Data Table 4 147 Limit Test 4 147 Marker Stats 4 148 Exceedance Stats 4 148 Curve Fit 4 148 Data Ta...

Page 201: ...settings 4 175 General System 4 176 Macros 4 176 Recall from Disk 4 176 Disk Buffers Menu 4 177 File Name 4 177 Current Directory 4 177 Load Trace Data ASCII 4 178 Load Trace Data binary 4 179 Buffer 4 179 Interval 4 180 Disk to Buffer 4 180 Buffer to Disk 4 181 Disk Upkeep Menu 4 182 File Name 4 182 Current Directory 4 182 Make Directory 4 183 Del File 4 183 Del Cur Dir 4 183 Format Floppy 4 183 ...

Page 202: ...e 4 199 Date 4 199 System Diagnostics Menu 4 200 Keypad Test 4 200 Keyboard Test 4 200 Knob Test 4 200 RS232 Printer Test 4 200 String to RS232 4 201 String to Printer 4 201 Memory Test 4 201 System RAM 4 201 System ROM 4 201 Video RAM 4 201 Help ROM 4 201 Disk Test 4 201 Serial Number 4 202 Program S N 4 202 Kill AutoOff 4 202 Edit Macro Menu 4 203 Special Keys 4 203 Macro String 4 203 Insert Rep...

Page 203: ...ctors of 2 A numerically entered value is rounded to the nearest allowable Span If the new frequency Span would extend below 0 Hz or above the Base Frequency then the Start and End frequencies will be adjusted Changing the Span will change the Linewidth Span FFT Resolution and Acquisition Time FFT Resolution Span The Linewidth and Acquisition time are other ways to change the Span The two displays...

Page 204: ...FSPN d f Acquisition Time Select the Acquisition Time of the active display The Acquisition Time is the time record length for the FFT FFT Resolution Span A numerically entered value is rounded to the nearest allowable Acquisition Time Changing the Acquisition Time will change the Span FFT Resolution Acquisition Time and Linewidth 1 Acquisition Time The Linewidth and Acquisition time are other way...

Page 205: ...se cross spectrum etc but the entry field can be linked or unlinked using the Link key If Analyzer Configuration is set to Dual Channel they field is automatically linked to both displays Command FLIN d i Base Frequency Select the FFT Base Frequency 102 4 kHz 100 0 kHz The Base Frequency sets the Full Span bandwidth for FFT and Correlation measurements All spans are derived from the base frequency...

Page 206: ...span The knob adjusts the Center frequency in steps equal to the Linewidth If an entered Center frequency is incompatible with the Span then it will be set to the closest allowed value This softkey also anchors the Center frequency Adjusting the FFT Span will leave the Center frequency unchanged Enlarging the frequency Span may change the Center frequency if the new measurement would extend below ...

Page 207: ... the measurement group is Correlation then the End frequency is always equal to the Span baseband The two displays can have different End Frequencies if the Analyzer Configuration is set to Independent Channels In this configuration no two channel measurements are allowed frequency response cross spectrum etc but the entry field can be linked or unlinked using the Link key If Analyzer Configuratio...

Page 208: ... 2 Octave Channels 1 1 Octave 125 mHz 16 kHz 1 3 Octave 160 mHz 20 kHz 1 12 Octave 190 mHz 6 17 kHz The total power of all measured bands is displayed as a filled in band at the right side of the graph The exact band center frequencies are calculated according to the ANSI standard The displayed frequencies are sometimes rounded to even values for a simpler display The measurement may span 1 to 11 ...

Page 209: ...ve Resolution Select the Octave Resolution number of bands per octave for the active display Full Third Twelfth Full octave band centers are calculated by multiplying or dividing 1000 Hz by 2 Third octave band centers are calculated by multiplying or dividing 1000 Hz by 21 3 or 1 2599 Twelfth octave band centers are calculated by multiplying or dividing 1000 Hz by 21 12 or 1 0595 The exact band ce...

Page 210: ...ndent The Highest Band for all Octave Resolutions is decreased by 2 in this case If 1 Octave Channel is selected then only one input may be analyzed If both displays are making an octave measurement they must both use the same input Changing the input of the active display will change the Measurement or input of the other display if necessary User Functions which use both inputs may not be measure...

Page 211: ...he Start frequency is usually less than the Stop frequency If the Start frequency is greater than the Stop frequency then the sweep proceeds downward from the Start frequency If the Start frequency is changed during a sweep the sweep will be reset Command SSTR d f Stop Set the Stop frequency 1 mHz 102 4 kHz Note that measurements at frequencies less than 1 Hz take a significant amount of time The ...

Page 212: ...asured Auto Resolution On allows the sweep to skip points if sequential points do not vary by more than a specified amount Auto Resolution is specified by three parameters the Faster Threshold the Slower Threshold and the Maximum Step Size These parameters can only be adjusted when Auto Resolution is On Auto Resolution examines the results of successive measurements If the newest measurement is wi...

Page 213: ...S d i Maximum Step Size Set the Maximum Step Size for Auto Resolution frequency sweeps 2 256 When Auto Resolution is On each successive time the Faster Threshold condition is met on BOTH channels the frequency step size is increased until the Maximum Step Size is reached This sets the maximum speed at which the sweep will continue until the Slower Threshold is exceeded Generally this number should...

Page 214: ...en the sweep returns to the previously measured point and moves to the very next frequency point in the sweep with no skipping The sweep continues from this point speeding up if allowed and slowing down when required This fills in skips in the sweep which vary by more than the Slower Threshold Measurements which differ by more than the Faster Threshold on EITHER channel but less than the Slower Th...

Page 215: ...that specified by Min RPM and a value calculated from the Max Order by the formula max Max RPM 60 40 000 Max Order Selecting a lower Max RPM will allow calculation of higher orders Command ORMX d f Min RPM This parameter does not affect the way order measurements are calculated by the SR785 It merely provides a default lower value by which to scale measurements whose x axis is RPM such as RPM prof...

Page 216: ...ck measurements use the memory allocated to the waterfall buffer you cannot use waterfall storage while Tracking is on Command OTRK d i Track Setup Displays the track setup submenu This submenu displays parameters which define the Track1 and Track2 measurements Track Points Sets the number of points for track measurements When the specified number of points have been acquired the measurement will ...

Page 217: ...be displayed without retaking any data Command O1TK d f Input Channel Track 1 Specifies the input channel associated with the Track 1 measurement Regardless of the input channel specified the SR785 always tracks all orders specified by the max order and delta order softkeys for both input channels The Input Channel Track 1 softkey merely selects which channel will be displayed Once a track measure...

Page 218: ...dless of the input channel specified the SR785 always tracks all orders specified by the max order and delta order softkeys for both input channels The Input Channel Track 2 softkey merely selects which channel will be displayed Once a track measurement is done or paused data for each channel can be displayed without retaking any data Command O2BN d i ...

Page 219: ...2s in powers of 2 If the base frequency is 100 0 kHz the allowed sampling times range from 3 91µs to 2 048s in powers of 2 Command SPAN d i Histogram Length Sets the number of points in each histogram The number of points can be specified in samples records each record is 1024 samples or in seconds When the specified number of samples records or seconds has been reached the histogram will update I...

Page 220: ...is frequency 3 91µs If set to 102 4 kHz the the fundamental sampling rate of the instrument is 262 144 kHz and the allowed sampling times will be multiples of the reciprocal of this frequency 3 814µs Command FBAS d i Repeat When repeat is set off the SR785 computes a single histogram and stops If repeat is on the analyzer will automatically acquire new histograms continually as each one is finishe...

Page 221: ... compute the frequency spectrum of finite time records The Correlation Measurement Group calculates the time domain auto and cross correlation of signals The Octave Analysis Measurement Group measures the power within logarithmically spaced frequency bands covering up to 11 octaves The Swept Sine Measurement Group uses the sine source to sweep a frequency range making optimized measurements at dis...

Page 222: ...um is the basic measurement of an FFT analyzer It is simply the FFT of a time record The spectrum is a complex quantity it contains phase as well as amplitude information This is sometimes referred to as the linear spectrum The phase of the spectrum is meaningful only if the time record is triggered with a fixed relationship to the input signal If the signal is periodic as well the signal and trig...

Page 223: ...re complex they have both a real and an imaginary part The sampling rate is always half of the equivalent baseband span Remember the time record is not a continuous representation of the input signal The data is sampled and has a time resolution of 1 sample rate High frequency signals will appear distorted in the time record However ALL of the spectral information is preserved by the Nyquist sampl...

Page 224: ...ween the two channels Vector averaging can be used to eliminate signals which do not have a constant phase relationship between the two channels In this case triggering is not required for vector averaging The magnitude is simply the product of the magnitudes of each spectrum Frequencies where signal is present in both spectra will have large components in the cross spectrum Frequency Response The...

Page 225: ...from within the device under test which is not related to the input signal it will result in a coherence of less than 1 0 Capture The capture buffer stores sequential time domain data in memory See Capture in Chapter 2 for more details The capture measurement displays the contents of the capture buffer FFT measurements can use this stored data as input data by choosing Playback as the Input Source...

Page 226: ...ons in Chapter 2 for more Measurement Correlation Select the Measurement of the active display when the Measurement Group is Correlation Each Measurement has an associated View Changing the Measurement changes the View to the View last used with the new Measurement Command MEAS d i The following Measurements are available in the Correlation Measurement Group Auto Correlation Auto correlation is a ...

Page 227: ... for measuring time delays between two common signals The definition of Cross Correlation depends upon the Average Mode selected in the Average menu Averaging Cross Correlation invFFT FFTu2 FFT1 Peak Hold or RMS Averaging On Cross Correlation invFFT FFTu2 FFT1 Vector Averaging On Cross Correlation invFFT FFTu2 FFT1 where FFT1 is the windowed FFT of Channel 1 and FFTu2 is the un windowed FFT unifor...

Page 228: ...d data data bandwidth starts at DC are captured The capture buffer resembles a digital oscilloscope display Signals at frequencies above 1 2 56 times the sample rate have been filtered out The capture buffer is not a continuous representation of the input signal The data is sampled and has a time resolution of 1 sample rate High frequency signals will appear distorted in the time record However AL...

Page 229: ...p with the real time capture but allows visual aliasing to occur Once capture is complete the display is redrawn showing the envelope of all points eliminating any visual aliasing effects To measure from a region of the buffer set the Playback Start and Length in the Input menu The capture data is filtered and down sampled according to the capture sample rate Only baseband data data bandwidth star...

Page 230: ...urce level Normalized Variance Normalized variance is a measure of the signal to noise ratio of a swept sine measurement after the signal has been integrated for a specified time or a specified number of cycles Variance values near 1 indicate that the final signal to noise ratio is high while values near zero indicate that the final signal to noise ratio is poor Cross Spectrum The swept sine cross...

Page 231: ...e In the case of several tach pulses per revolution the choice of which tach pulse is arbitrary but is consistent from record to record Power Spectrum The Order Power Spectrum displays the power in the input signal as a function of order multiple of the rotation frequency It is derived from the Linear Spectrum by multiplying each point by its complex conjugate Time Record The order time record dis...

Page 232: ... the capture buffer Order measurements can use this stored data as input data by choosing Playback as the Input Source in the Input menu In the order measurement group the capture buffer stores tachometer information as well as input data Therefore only a capture buffer which was taken while the instrument was in the order group can be used as a source of playback data for order measurements Note ...

Page 233: ...g frequency is decreased and may contain aliased signals While this is important for the frequency domain measurements in the FFT measurement group it is not a consideration in time histogram group where the goal is to represent the original signal as closely as possible Capture The capture buffer stores sequential time domain data in memory See Capture in Chapter 2 for more details The capture me...

Page 234: ...x is the real part and y is the imaginary part The Y axis of the display is logarithmic If dB Units in the Units submenu are Off the Y axis will display a logarithmic grid If db Units are On the Y axis will have a grid which is linear in decibels The shape of the graph is the same in the two cases Linear Magnitude Linear magnitude view graphs the magnitude of the measurement data The magnitude is ...

Page 235: ...uppress sets the phase of small data values to zero This avoids the messy phase display associated with the noise floor Remember even a small signal has phase Set the phase suppress threshold in the Display Options menu The FFT can be thought of as a set of bandpass filters each centered on a frequency bin The signal within each filter shows up as the amplitude of each bin If a signal s frequency ...

Page 236: ...surement data such as baseband time record have zero imaginary part This view is entirely along the X axis Nichols Plot The Nichols plot graphs complex measurement data as log magnitude along the Y axis versus unwrapped phase along the X axis The Y axis is logarithmic and the X axis is linear Adjacent frequency points are connected by a line This view is generally meaningful only for measurements ...

Page 237: ...shown with a logarithmic y axis If dB units is on the graph will be shown with a y axis linear in dbs Setting this softkey to dBm will convert measurement results to decibels relative to 1 mW The voltage to power conversion is done by assuming that power volts volts impedance where impedance is the setting of the dBm Ref Imped softkey dBspl will convert measurement results to sound pressure level ...

Page 238: ...imply 10 log power 1mW where power Vrms2 Reference Impedance Command DBMR f Y Max Set the Y Maximum top reference of the active display The top reference is the Y value of the top of the graph The top reference has the same units as the display When Y Max is changed the value of Y Min is kept fixed and Y mid and Y Div are adjusted The two displays can have different top reference values This entry...

Page 239: ...enter reference to the current Marker X Position The Y Maximum and Y Minimum are adjusted to give the effect of vertical zooming Entering a scale numerically leaves the Y Min bottom reference unchanged The Y Max and Y Mid are adjusted If the View is Log Mag and dB Units are set Off then the graph will be logarithmically scaled In this case the box will display the total number of decades along the...

Page 240: ...ys can have different Y Center values This entry field can be linked to both displays using the Link key Command YCEN d x Y Div Polar Set the Y Division scale of the active display when the view is Nyquist or Nichols plot This value is the vertical scale of the graph The knob adjusts the scale in a 1 2 5 10 sequence Changing the scale does not change the Y Center location If the Y axis is scaled l...

Page 241: ...xamining closely spaced details in a display without changing the measurement Expansion is about the Marker Position whenever possible Use Pan to translate a zoomed display Zoom is not allowed when the X axis is logarithmic or when the View is polar Nyquist or Nichols plot The two displays can have different Zoom values when expanded This entry field can be linked to both displays using the Link k...

Page 242: ...lled to the display from disk or memory Since an Off Line display is showing old data its Measurement Window Frequency Span and Averaging may not be modified Only display related parameters such as View Scaling and Marker Functions may be changed Off Line The two displays can have different Display Update Modes This entry field can be linked to both displays using the Link key A single display may...

Page 243: ...ey Octave Analysis is always displayed on a logarithmic X axis The X axis type for Swept Sine measurements is set by the Sweep Type This softkey is disabled for the Octave Analysis Swept Sine Order and Time Histogram Measurement Groups The logarithmic scale does not affect the frequency bins of the FFT measurement The resolution is still linear The points are simply graphed with a logarithmic axis...

Page 244: ...w is displayed with a rectangular grid In this case X Center Y Center Y div and X div are all individually adjustable If the grid is set to polar a polar grid is displayed In this case X center and Y center are fixed at 0 Y div is adjustable and gives the number of Y units in each radial spoke of the grid Command GDIV d i Phase Suppress Set the Phase Suppress Threshold for the active display 0 Whe...

Page 245: ... 1 The aperture is used in the calculation of d dx and group delay in user math functions Larger windows result in smoother graphs with less x axis resolution Derivative calculations are not available in Octave Analysis measurements and this menu box cannot be changed The two displays have their own d dx Window The same function may viewed in the two displays with different d dx windows This entry...

Page 246: ...oosing Minimum for the Marker Seeks selection Link moves the Marker Region in the other display with the Marker Region in this display The marker setup of the other display still configures its marker display Each display has its own Marker Tracking This entry field can be linked to both displays using the Link key Command MRKR d i Mode Select the Marker Mode of the active display Normal Harmonic ...

Page 247: ... memory Use the knob without Alt to move the marker along the X axis within a record Harmonic The Harmonic Marker Mode defines a Fundamental Marker with a solid vertical line In addition to the Fundamental Marker a number of harmonics are identified by small triangular Harmonic Markers The Marker Position Display can show the position of the Fundamental or of a single Harmonic The Total Harmonic D...

Page 248: ...e connected by shaded bands at the bottom of the graph These shaded bands define the bins within the Upper and Lower bands Use Modify Band to modify either the Upper or Lower band Use the knob to move selected band Use Alt knob to re size the selected band The two Band Powers are calculated within the Marker menu in Vrms Only those frequencies within the two band limits contribute to the Band Powe...

Page 249: ...and damping ratio for a single degree of freedom in a frequency response curve The fit area is moved using the knob Use Alt knob to re size the fit region The Frequency Damping cursor should only be used with frequency response data The Frequency Damping Cursor is only available in the FFT and Swept Sine measurement groups ...

Page 250: ...he Seeking the Mean the X position is the center of the Marker Region and the Y position is the Mean of the data within the region Each display has its own Marker Seeks Mode This entry field can be linked to both displays using the Link key Command MSEK d i Width Select the Normal Marker Width of the active display Spot Normal Wide The Normal Marker Mode defines a Marker Region between two solid v...

Page 251: ...ay calculates the marker position relative to the other display s marker position The marker offset is just the marker position of the other display This is generally valid only if the two displays have a similar measurement Pressing Marker Ref changes from Off to Rel and sets the Marker Offset to the current Marker Position Marker Ref again changes from Rel back to Off Marker Ref does not change ...

Page 252: ...g the display units invalidates the Marker Offset Re enter the Marker Offset or use Marker Ref to reset the Marker Offset in the new units Pressing Marker Ref changes from Off to Rel and sets the Marker Offset to the current Marker Position Marker Ref again changes from Rel back to Off Each display has its own Normal Marker Y Offset This entry field can be linked to both displays using the Link ke...

Page 253: ...nt units of the x axis If the exact x value specified is not available the marker will be sent to the closest available X value Target Specifies the X position the marker will be sent to with the Marker X to button The target is entered in the current units of the x aaxis If the exact x value specified is not available the marker will be sent to the closest available X value ...

Page 254: ...nics within the measurement span which are identified by the Harmonic Markers contribute to the THD calculations The harmonic identification works best if the fundamental frequency is a bin frequency If the fundamental is off bin then it is best to use the Flattop window to broaden all of the peaks Each display has its own Number Of Harmonics This entry field can be linked to both displays using t...

Page 255: ...onic or Sideband in either Absolute units or Relative to the fundamental Relative Mode reports the amplitude of the selected harmonic or sideband relative to the fundamental The marker amplitude units are dBFundamental The frequency is always absolute Each display has its own Readout Mode This entry field can be linked to both displays using the Link key Command HRDO d i THD This menu box displays...

Page 256: ...60 Harmonic Marker Menu SR785 Dynamic Signal Analyzer Marker The result is shown in Vrms or dBVrms depending on the setting of dB Units To convert a value in Vrms to power square the result Command HPWR d ...

Page 257: ... within the measurement span which are identified by the Sideband Markers contribute to the Sideband Power calculations Each display has its own Sideband Separation This entry field can be linked to both displays using the Link key Command SSEP d f Sidebands Select the Number Of Sidebands for the active display 1 50 The first upper sideband fundamental separation is identified as 1 the first lower...

Page 258: ...to the selected harmonic or sideband If the selection is not within the measurement span the marker will move to the highest or lowest measured frequency which will be reported as the marker position Each display has its own harmonic sideband display This entry field can be linked to both displays using the Link key Command HDSP d i Readout Mode Select the Readout Mode for the Harmonic and Sideban...

Page 259: ...nd SPWR d i RMS Sideband Power This menu box displays the Sideband Power of the active display The Sideband Power is the sum of the squared magnitudes of the sidebands Only those sidebands within the measurement span which are identified by Sideband Markers contribute to the calculation The result is shown in Vrms or dBVrms depending on the setting of dB Units To convert a value in Vrms to power s...

Page 260: ...ition display denotes Lower or Upper Band Marker Command BMKL d i j or BMKR d i j Band Exclude Select Band Exclusion for the Band Marker in the active display none 1from2 2from1 None means that the two bands are independent and include all bins within their left and right limits 1from2 means the bins in band 1 Lower are excluded from the band 2 Upper power The region where the two bands overlap is...

Page 261: ... example to measure THD N use the Lower 1 band to define a small region around the fundamental and the Upper 2 band to define the total bandwidth of interest Exclude 1from2 so the Upper 2 band does not measure the fundamental Choose the 2 1 2 ratio mode to measure THD N power with fundamental notched out total power including fundamental Command BRAM d i Band Power This menu box displays the Upper...

Page 262: ... Command MMCA d Frequency Displays the resonant frequency of the data in the cursor area The resonant frequency is calculated by fitting a single pole frequency response function to the data The resonant frequency is the imaginary part of this pole Command MMCA d Damping Ratio Displays the damping ratio of the data in the cursor area The damping ratio frequency is calculated by fitting a single po...

Page 263: ...ne when making triggered measurements without the source Source Off Turn off the source output The output is held at 0 V If a triggered source is selected Chirp Burst Chirp Burst Noise or Arbitrary the phase of the measurement is relative to the source not the trigger Command SRCO i Source On Turn on the source output The output is determined by the selected source type Command SRCO i Sine Set the...

Page 264: ...chirp repeats over and over Trigger Caution If the Chirp source is selected the triggered FFT measurement phase is stable only if the input signals are derived from the triggered source output Turn the source off or set it to Sine when making triggered measurements of external signals not the source Command STYP i Noise Set the source output to Noise and display the Noise Setup menu The output is ...

Page 265: ...trace The Capture buffer is filled by capturing an input signal The Arbitrary source can play a portion of memory starting at a specified point The output sampling rate can also be specified The amplitude of the source is set relative to 1 V up to a maximum of 5 V Triggering The Arbitrary source is triggered by External triggers Set the Trigd Source Mode to trigger once 1 Shot or with every trigge...

Page 266: ...e Arbitrary source is selected the triggered FFT measurement phase is stable only if the input signals are derived from the triggered source output Turn the source off or set it to Sine when making triggered measurements of external signals not the source Command STYP i ...

Page 267: ... with an FFT Base of 100 0 kHz The keypad allows arbitrary frequencies to be entered Remember the output is periodic over the FFT time record only if the frequency is an exact multiple of the Linewidth Source Trigger will not result in a stable phase for non periodic frequencies The sine source is not triggered The output is always continuous Command S1FR f Amplitude 1 Set the peak Amplitude of To...

Page 268: ...idth of the active display FFT Span The knob always sets the frequency to an exact multiple of the Linewidth For octave analysis the Linewidth of the most recent FFT Spans are used with an FFT Base of 100 0 kHz The keypad allows arbitrary frequencies to be entered Remember the output is periodic over the FFT time record only if the frequency is an exact multiple of the Linewidth Source Trigger wil...

Page 269: ...would be 1 400 26 dB relative to the peak However the chirp waveform is identical from time record to time record and each component has a fixed phase relative to all the other components This worsens the crest factor by a few dB and reduces the amplitude of each component for a specified peak amplitude The input dynamic range of the measurement is reduced when using the chirp source Command CAMP ...

Page 270: ...The Source Display only applies for the FFT Measurement Group The Source Display is the display which determines the burst period FFT time record and the bandwidth for bandlimited noise and chirp FFT Span There is a single Source Display for both Chirp and Noise outputs Changing this entry for one type of source also changes it for the other Select which display sets the time record and frequency ...

Page 271: ...not perfectly defined Command NAMP x Type Select the Type of noise output White Pink Bandlimited White or Pink White Noise White noise provides equal noise density V Hz from 0 to above 102 4 kHz regardless of the measurement bandwidth of the displays The spectrum of white noise appears flat in an FFT spectrum The power spectral density PSD remains constant at all spans Pink Noise Pink noise rolls ...

Page 272: ...he measurement and waterfall In the Continuous case the source triggers on every trigger with a minimum trigger period set by the time record of the Source Display FFT Correlation Time Histogram or the Source Period Octave Order Source trigger outputs a noise burst every source period or FFT time record The FFT time records are synchronized to the burst Free Run Trigger Mode outputs a noise burst ...

Page 273: ...0 the burst noise source is triggered by External triggers Set the Trigd Source Mode to trigger once 1 Shot or with every trigger Continuous In the 1 Shot case the burst source only triggers on the first trigger after Start Reset This same trigger starts the measurement and waterfall In the Continuous case the source triggers on every trigger with a minimum trigger period set by the Source Period ...

Page 274: ...ata ranges from 1 0 to 1 0 A value of 1 0 is output at 1V when the Amplitude is 100 When playback is from a Capture buffer the input range corresponds to full scale For example if a 0 1 Vpk 20 dBV signal is captured on an Input Range of 20 dBV full scale at the input it will play back at 1V when the Amplitude is 100 To duplicate the actual signal amplitude set the Amplitude to 10 Command AAMP i So...

Page 275: ... Rate is LESS than the maximum sampling rate the output will contain alias frequency components above 1 2 the sampling rate In general the frequency span of any measurement using this source should not exceed 1 2 times the Play Rate to avoid measuring these alias frequencies Command ARAT i Source Select Arbitrary waveform playback from the Arbitrary Waveform memory or from a Capture buffer Use the...

Page 276: ...e from a Capture Buffer and the Measurement of the active display must be the Capture Buffer for this key to be active Choose the correct Capture Buffer as the Measurement and use Zoom and Pan to show the region of interest Press Set Left Edge to set the Arbitrary Source Start to the marker position The Arbitrary Source Length is not changed If the requested Source Start plus the Source Length in ...

Page 277: ...he Arbitrary Source waveform The Arbitrary Source can also use the capture buffer as the output waveform Clear Allocation Clears the existing memory allocations in this menu Confirm Allocation Places the memory allocations in this menu into effect Exiting this menu without pressing Confirm Allocation will cancel any adjustments made in this menu Command MALC i j k Trace to Arb Copy the real part o...

Page 278: ...s an Arbitrary waveform Non baseband time records or complex traces do not reproduce well The amplitude of the Arbitrary Waveform is normalized to the maximum value in the Trace The largest trace value is considered full scale 100 amplitude 1V Be sure to set the Play Rate to the appropriate value to reproduce the frequencies in the trace correctly Command TARB i ...

Page 279: ...or Channel 2 input Generally this is useful for frequency response functions with substantial gain as well as attenuation Input Auto Ranging is turned on for both inputs when Auto Level is on Whenever Auto Level is used the measurement MUST be frequency resonse The Auto Level Reference Channel determines which input will be maintained at the Ideal Reference Level This is usually the device under t...

Page 280: ...n of the source amplitude may result in a Reference Channel signal which is not within tolerance of the Ideal Reference The Ideal Reference may be changed at any time during a sweep Command SSRF x Source Ramping Select the Source Ramping Mode Off On If Source Ramping is Off source level changes are made instantly If Source Ramping is On source level changes are made at the Source Ramp Rate Settlin...

Page 281: ...it must be less than or equal to this limit If the required source amplitude is very small the resolution of the source amplitude may result in a Reference Channel signal which is not within tolerance of the Ideal Reference The Reference Upper Limit may be changed during a sweep Command SSUL x or SSLL x Reference Lower Limit Set the Reference Lower Limit 0 1 dB 30 0 dB This parameter is adjustable...

Page 282: ...e Maximum Source Level In this case the Reference Channel may fall below the Reference Lower Limit The Maximum Source Level may be changed at any time during a sweep Command SMAX x Offset Set the DC Offset of the Swept Sine Source 5V 5V The offset resolution is 0 1 mV Note that the sum of the offset and Amplitude if Auto Level Reference is off or Maximum Source if Auto Level Reference is on cannot...

Page 283: ... sine measurements Both displays use the same Input Source for their measurements The Analog Playback indicator shows the input source at the top of the screen Command ISRC i Analyzer Configuration Select the analyzer configuration Independent Channels Dual Channel Independent Channels allows the two displays to have different frequency parameters For instance Display A could be set to full span w...

Page 284: ... will periodically perform an input offset calibration This involves internally grounding both inputs and correcting their DC offsets This only takes a second However the measurements will need to settle again after an offset calibration To avoid disrupting a lengthy measurement turn Auto Offset Off A warning message is displayed 15 seconds before an Auto Offset calibration is performed Pressing b...

Page 285: ...t both inputs Input Mode Select the Input Mode for the selected input A single ended A B differential The Input indicator shows the current mode at the top of the screen In general when looking at very small signals connect A to the signal source and B to the signal ground and use A B In this case make sure that the two input cables do not encompass any loop area twist them together or run them si...

Page 286: ...put Range for the selected input 50 dBV 34 dBV The Input Range is the full scale signal input just before overload The actual underlying Input Range of the SR785 varies by 2 dB steps from 50 dBVpk to 34 dBVpk The input range can be set in units of dBVpk dBVrms dBVpp Vpk Vrms dBEUpk dBEUrms dBEUpp EUpk EUrms or EUpp If a value is entered in one of these units the closest actual hardware input range...

Page 287: ...ting filter conforms to ANSI standard S1 4 1983 A B and C Weighting functions are also available as operators in User Math functions Command I1AW i Command I2AW i Autoranging Select the AutoRange Mode for the selected input Up Only Tracking This mode only applies when Ch1 Auto Range is On In Up Only only overload causes the Input Range to change The Input Range only moves up In Tracking Mode the I...

Page 288: ...of interest Measurements of inputs which are assigned units of acceleration velocity or displacement may be displayed with any of these three units using Transducer Convert in the Input Transducer Parameter submenu Engineering Units Select Engineering Units for the selected input On Off Measurements which require input data from an input which has Engineering Units On will be displayed with units ...

Page 289: ...channel unlike most softkeys which apply to a specific display Command EU1L i Command EU2L i EU Volt Set the Engineering Units per Volt scale factor for the selected input This factor is used to scale the display units from Volts to Engineering Units when Engineering Units are On The displayed units change from Volts to the EU Label The EU scale factor may be entered in EU V V EU or dB EU V Note t...

Page 290: ...ic display Command EU1U s EU2U s Transducer Convert Select the Transducer Conversion for the selected input Transducer conversion only has an effect for measurements of inputs with Transducer Units of acceleration velocity or displacement Transducers such as accelerometers convert a physical quantity such as acceleration into a voltage at the analyzer s input By assigning Transducer Units to an in...

Page 291: ... can be set to trigger 5V 25V TTL If TTL is selected the tachometer will trigger on a TTL rising edge If 5V is selected the tachometer trigger level can be set from 5V to 5V with 40 mV resolution If 25V is selected the threshold resolution is 200 mV TTL Trigger range will yield the best phase accuracy Command TARG i Tach Level Sets the tachometer trigger level when the trigger range is set to 5V o...

Page 292: ...gh the threshold several times for a given tachometer pulse set the holdoff time long enough to prevent retriggering for each tach pulse Command TAHO i Tach Hold Off Specify the interval during which the tachometer input is prevented from triggering when tachometer hold off is enabled For a noisy tachometer signal the tachometer holdoff time should be set long enough so that the tachometer trigger...

Page 293: ...he corresponding start time relative to the start of the buffer is displayed as well Both channels playback starting at the Playback Start Command ISTR i Playback Length Select the Capture Playback Length in 2 kPoint 2048 points increments The Playback Length in points plus the Playback Start cannot exceed the Capture Length of the buffer The corresponding playback time is displayed as well Both c...

Page 294: ... Circular In 1 Shot playback the buffer is played a single time The playback halts when the end of the buffer is reached In Circular playback the playback starts over when the end of the buffer is reached There is often a discontinuity in the playback measurement when the playback jumps from the end to the start of the buffer In either mode press Start Reset to restart playback at the start again ...

Page 295: ...e records are overlapped there may be more than 256 measurements to display and playback will take even longer When the measurement time records are very long narrow spans the time to process and display each measurement is much less than the real time record length Since the data is already available in the capture buffer Normal Speed playback means waiting unnecessarily for a real time record to...

Page 296: ...e a trigger event will be recognized Auto Arm arms the trigger automatically whenever possible without waiting for an arming event The combination of Auto Arm Trigger Mode and the Continuous Trigger Source is often known as Free Run triggering since the analyzer will take data as quickly as possible In Manual Arm the trigger is armed only after Manual Arm is pressed or the TARM interface command i...

Page 297: ... will take data as quickly as possible Ch1 or Ch2 internally trigger on the Ch1 or Ch2 input signal The trigger is detected after the anti aliasing filter if On External and Ext TTL trigger on the front panel Trigger Input External has a variable Trigger Level and Ext TTL triggers on TTL signals Manual triggers with Manual Trigger or an interface command Use Auto Arm Trigger Mode with Manual Trigg...

Page 298: ... Trigger Delay applies only to FFT and Correlation measurements When the Analyzer Configuration is Dual Channel the delay setting affects the Ch1 input When the Analyzer Configuration is Independent Channels the delay setting affects the measurement displayed in Display A The triggered time record does not have to start with the trigger event The time record can start before the trigger negative d...

Page 299: ...er is set to Auto Arm Continuous the source is output continuously and this menu box is ignored Triggering The triggered sources are triggered by External triggers In the 1 Shot case the source only triggers on the first trigger after Start Reset This same trigger starts the measurement and waterfall This is useful when the source length is very long compared to the measurement time or many measur...

Page 300: ...PM Sense is Increasing or must be below the threshold if Delta RPM Sense is Decreasing If Delta RPM sense is set to Abs Change the Start RPM is ignored Command TRSR f Start RPM On Off Activates the Start RPM threshold If Start RPM is set On the trigger will not be armed until the RPM passes the threshold If Start RPM is Off the threshold setting is ignored If Start RPM is On the RPM threshold must...

Page 301: ...m repetitively with this time interval Command TIAS f Manual Arm Manually arm the trigger This function only applies if the Trigger Mode is Manual Arm Manual Arm enables triggering after Start Reset only after the trigger is armed using Manual Arm or from an interface command Once the trigger is armed the next trigger event will trigger the measurement For FFT correlation and Time Histogram measur...

Page 302: ...r For FFT correlation and Time Histogram measurements each time record requires the trigger to be re armed For octave and swept sine measurements the first trigger after arming starts the measurement and subsequent triggers are ignored Command TMAN ...

Page 303: ... active display If the Analyzer Configuration is Dual Channel the averaging parameters are the same for both displays Averaging successive measurements together improves accuracy and repeatability Compute Averages Turns the computation of averages on and off If Compute Averages is off no averaged quantities will be computed or displayed Although this results in a slight improvement in the speed of...

Page 304: ... is known as Fixed Lenth averaging This means that a fixed number N of measurements are compared to determing the peak Waterfall Storage If Waterfall Storage is on the waterfall buffer only stores the completed linear averages not each individual measurement Each time the linear average is done the result is stored in the waterfall buffer and the average is reset and started over instead of stoppi...

Page 305: ... key Command FAVN d i Display Average Select the type of averaging for the measurement displayed on the active display None RMS Vector Peak Hold Note that when Compute Averages is On the SR785 always computes the non averaged rms averaged vector averaged and peak hold averaged version of all measurements simultaneously The Display Average softkey only determines which version of the measurement is...

Page 306: ...ther measurements the definition of the vector averaged measurement depends upon the measurement Vector averaging is often called time averaging since vector averaging in the frequency domain yields the same value as taking the FFT of the averaged input time record Linear averaging computes the equally weighted mean of X and Y over N measurements Exponential averaging weights new data more than ol...

Page 307: ...crement is less than or equal to 100 the measurement is said to be real time All time points contribute to one or more measurements If the increment is 200 the start of the next time record is advanced from the start of the previous time record by 2 time records leaving a gap of 1 record This means that the data between the two time records is not measured When the Time Record Increment is greater...

Page 308: ...t the measurement is not settled Once the 4th measurement is complete the display returns to full intensity since the measurements have completely settled time records If averaging is on changes which unsettle the measurement will restart the average Unsettled measurements are not included in the new average Averaging does not start until the measurement is settled When the time record increment i...

Page 309: ...or Timed When averaging is on Average Preview allows each individual measurement to be accepted added to the average or rejected not added to the average based upon the input time records This is useful for rejecting bad time records from corrupting an averaged measurement When Average Preview is Manual each input time record is displayed after it is acquired Choose Accept or Reject to either use ...

Page 310: ...pt the displayed preview time record and add the measurement to the average Average Preview allows each individual measurement to be accepted added to the average or rejected not added to the average based upon the input time records This is useful for rejecting bad time records from corrupting an averaged measurement Command PAVA Reject Reject the displayed preview time record and do not add the ...

Page 311: ...eparately This entry field can be linked to both displays by using the Link key Command OTYP d i Linear Time The band filter outputs are equally weighted and averaged for an Integration Time While Linear averaging is in progress the integration time completed is shown in the Horizontal Scale Bar below the graph When the Integration Time has been completed the measurement stops and Done is displaye...

Page 312: ... that there is a 68 probability that the results are within the specified Confidence Level of the true mean for every band in the measurement There is a 96 probability that the results are within twice the Confidence Level in dB of the true mean The effect of Equal Confidence averaging is that higher frequency bands have shorter time constants and lower frequency bands have longer time constants T...

Page 313: ...ay be selected In addition to the octave bands a broadband sound level is measured and displayed as the last band in the octave graph Exponential averaged sound power Leq is calculated according to ANSI S1 4 1983 Type 0 Broadband Impulse and Peak measurements are made according to IEC 651 1979 Type 0 Exponential averaged power Leq Impulse I and Peak P power are computed from real time input data T...

Page 314: ...t is started with a trigger This mode is useful for measuring reverberation where the first measurement is triggered with the noise burst use the Burst Noise source with 1 Shot Trigd Source Mode and subsequent measurements follow continuously All complete averages are stored to a waterfall to examine the sound level decay Both displays always have the same Linear Average Trigger Command OLAT d i ...

Page 315: ...ing a sweep take effect immediately The estimated sweep time is displayed in the Horizontal Scale Bar This time is simply the sum of the Settle and Integrate times for all points in the sweep Auto functions Source Auto Level Auto Range Auto Resolution will change the actual sweep time Command SSTM d x Settle Cycles Set the number of Settle Cycles 1 32767 At each frequency point a settling time is ...

Page 316: ... lowest frequency in the sweep Changes made to the Integration Time during a sweep take effect immediately The estimated sweep time is displayed in the Horizontal Scale Bar This time is simply the sum of the Settle and Integrate times for all points in the sweep Auto functions Source Auto Level Auto Range Auto Resolution will change the actual sweep time Command SITM d x Integration Cycles Set the...

Page 317: ... detected noise at higher frequencies Changes made to the number of Integration Cycles during a sweep take effect immediately The estimated sweep time is displayed in the Horizontal Scale Bar This time is simply the sum of the Settle and Integrate times for all points in the sweep Auto functions Source Auto Level Auto Range Auto Resolution will change the actual sweep time Command SSCY d i ...

Page 318: ...ss Cancel to exit back to the main User Math menu To enter an equation use Operands and Operations and the knob to select operands and operations Backspace deletes the term before the cursor To edit an equation use Func String and the knob to move the flashing cursor within the equation Delete will delete the highlighted term Operands and Operations will either insert or replace at the cursor Use ...

Page 319: ...ayed Operands and press Enter to place it in the equation at the cursor location The display then automatically switches to the Operations display To enter another operand instead press Operands again The available measurement operands depend upon the current Measurement Group FFT Measurement Group ...

Page 320: ...4 124 User Math Menu SR785 Dynamic Signal Analyzer Correlation Measurement Group Octave Measurement Group Swept Sine Measurement Group Order Measurement Group ...

Page 321: ...e also triggered just like the normal measurements Operands which are measurement results which are not enclosed in angle brackets such as FFT1 or Time1 represent unaveraged instantaneous versions of the measurement Operands which contain an explicit averaging type such as Vec F1 or PeakHold F2 always are averaged according to their indicated type regardless of the setting of the Display Average s...

Page 322: ...ed by all 3 Measurement Groups Operations Use the knob to pick one of the displayed Operations and press Enter to place it in the equation at the cursor location The display then automatically switches to the Operands display To enter another operation instead press Operations again The available operations depend upon the current Measurement Group FFT Measurement Group Correlation Measurement Gro...

Page 323: ...order to produce meaningful results View operations Mag Mag2 Phase Real Imag simply convert the complex operand array into the desired form Mag and Mag2 compute the magnitude x2 y2 or magnitude squared x2 y2 with a real result Phase computes the phase tan 1 y x unwrapped with a real result Real simply zeroes the imaginary part Imag zeroes the real part Conj Ln Exp and Sqrt are defined as follows C...

Page 324: ...es For example to convert d dx to d df for a linear frequency display divide by the frequency spacing of the bins In the case where the X axis is logarithmic the function needs to correct for d logx dx The d dx operator requires a smoothing aperture or window GrpDly is the group delay operator Group delay is simply dθ dω Use Display Options d dx Window to set the aperture This operator yields vali...

Page 325: ...urement and then clear the equation Cancel Discard any changes made in this menu and exit this menu Enter Eq Enter the displayed equation as the new User Function and exit this menu The new User Function definition is used immediately if it is being displayed If the new function uses an incompatible or empty Trace it may not be displayed as a measurement If a display is already measuring this func...

Page 326: ...nd the magnitude and phase are updated Command USRC i x y Mag Enter a new value for the magnitude of the selected Constant The phase is left unchanged and the real and imaginary parts are updated Phase deg Enter a new value for the phase in degrees of the selected Constant The magnitude is left unchanged and the real and imaginary parts are updated Marker to Mag Copy the marker reading exactly as ...

Page 327: ...only for exact bin frequencies and very poor frequency selectivity This window is a poor choice for continuous signals In general this window is only useful when looking at transients which do not last the entire time record The uniform window may also be used with signals which are exactly periodic in the time record such as a chirp The uniform window is also useful in the order analysis measurem...

Page 328: ...or selectivity The off bin amplitude variation is the same as the BMH about 0 8 dB The Kaiser window is the best window to use for measurements requiring a large dynamic range Force Exponential The Force window is uniform over the beginning of the time record and zero over the remainder The force length is user specified This window is used to isolate impulsive signals such as impact excitations f...

Page 329: ... selected window is Force Exponential Command W1FE i Channel 2 Window Selects whether the Force or Exponential window is applied to the Channel 2 input This softkey is only active if the selected window is Force Exponential Command W2FE i Force Length Set the Force Window Length The maximum value that can be entered is the length of the FFT time record Points in the time record up to the Force Len...

Page 330: ...ata trace Use the knob to pick a trace and press Enter Window to Trace always stores a trace with 2048 points This corresponds to the longest possible time record 800 line baseband Using this trace in User Math requires attention to the lengths of other operands in any user function Command WITR d i Window Form Select the Window Form of the User window Non Symmetric Symmetric This softkey only aff...

Page 331: ...wn graphically their data has not been saved and may not be accessed in any way In this case the display updates and scrolls as quickly as possible Waterfall display WITH storage shows only those records which are stored in waterfall memory While the measurement is running the display scrolls down and the newest record is added to the top back While running the display may not update fast enough t...

Page 332: ...Waterfall Storage mode Waterfall storage is not available for Swept Sine measurements Storage Off does not store any measurements to waterfall memory and changes the Waterfall Display to a graphical scroll only Continuous storage adds measurement records to the waterfall memory until Pause Cont is pressed The last Total Count number of records are saved in memory and may be displayed One shot stor...

Page 333: ... is required to hold measurements with higher resolution The Total Count is limited to 2048 records per display regardless of the amount of installed memory The rate at which measurement records are added to waterfall memory is set by the Waterfall Skip This allows the waterfall memory to hold a longer time history as well as setting a variable storage rate Command WTOT d i Skip Storage Interval S...

Page 334: ...ndent of the Total Count number of records stored The View Count is the Z axis scaling of the waterfall display and should be less than the Total Count in order to use the display area effectively Setting the View Count to a large number 40 or so will cause the display to skip some records In this case every nth record is drawn in order to show the desired View Count range of the waterfall buffer ...

Page 335: ...o moves the marker from record to record along the Z axis and scrolls the display through the waterfall buffer Marker to Z is a faster way to move to an arbitrary record The marker position along the Z axis is displayed in the Marker Position Bar next to the marker frequency or time The Z axis position is the record number starting from 0 most recently stored at the back of the waterfall Record to...

Page 336: ...aces the memory allocations in this menu into effect Exiting this menu without pressing Confirm Allocation will cancel any adjustments made in this menu Command MALC i j k More Display the More Waterfall menu Press Return or Waterfall for the main Waterfall menu Trace Height Set the Waterfall Trace Height for the active display 20 80 The Trace Height specifies the percentage of the display height ...

Page 337: ... Position Bar displays the actual data value in all cases Each display has its own Waterfall Threshold This entry field can be linked to both displays by using the Link key Command WTHR d i Hidden Lines Set the Waterfall Hidden Line Mode for the active display Invisible Visible In a waterfall display as the older records scroll downward they are considered to move towards the front of the display ...

Page 338: ...from record to record in the Z axis and scroll the display through the waterfall memory Use the knob without Alt to move the marker along the X axis within a record Command WTRC d i j Slice to Trace Save a time slice from the waterfall to a Trace A slice is the history of a single X position data at the marker X position from all stored records Choose a Trace with the knob and press Enter to compl...

Page 339: ...group is order Capture Channels is always set to Ch1 Ch2 Turn off Auto Offset during capture to avoid interrupting the input signal Command CCHN i Capture Mode Select the Capture Mode 1 Shot Continuous Press Start Capture to begin storing data in the capture buffer If the Capture Mode is 1 Shot capture stops when the buffer is full Press Stop Capture to halt capture before the buffer is full If th...

Page 340: ... 0 kHz OR the Measurement Group is Octave If the selected capture Sampling Rate is the maximum rate then the digitized input data is stored in the capture buffer If the Sampling Rate is less than the maximum rate the input data is filtered and downsampled to the desired rate and then stored in the capture buffer This allows the capture buffer to hold a longer time period of data at a lower bandwid...

Page 341: ...nnot exceed the Total Available memory It may be necessary to decrease one allocation in order to increase another Command MMEM Capture Memory Capture Memory allocates memory blocks for the capture buffer The allocated Capture Memory sets the limit for the Capture Length Command MALC i j k Waterfall Memory Waterfall Memory allocates memory blocks for waterfall storage Command MALC i j k Arb Memory...

Page 342: ...sed View Header View information about the capture buffer data Auto Pan Set Auto Pan On or Off Auto Pan On automatically pans zoomed capture buffer displays to keep up with capture fill and playback The measurement must be a capture buffer and the display needs to be Zoomed in order for this to have any effect During capture fill this keeps the capture display showing the new points being added to...

Page 343: ...e frequency domain will revert to bin locations if the measurement is changed to the time domain and vice versa Data Tables are generally only applicable for the domain time or frequency and span in which they were originally defined Limit Test Display the Limit Test menu for the active display Limit Testing tests the measurement results against a set of defined Limit Segments When display data ex...

Page 344: ...ues even when this menu is not displayed Return to this menu to see the latest statistical values Exceedance Stats Display the Exceedance Statistics menu This menu is used to calculate Ln exceedance centile from Octave or FFT measurements stored in the waterfall buffer The calculation of Ln requires that the active display have records stored in the waterfall buffer The display must be paused or d...

Page 345: ... mathematical model that can be compared with actual data The SR785 does curve fitting and synthesis in two curve tables Each table contains a model of frequency response function containing up to 20 poles and zeros The model can be expressed in pole zero format pole residue format or polynomial format Either table can be synthesized into a trace When fitting the best fit model is calculated and p...

Page 346: ... is turned On Move the marker to the desired frequency or time and press this key to insert a new line in the Data Table The new line will be inserted after the highlighted entry To select an entry in the table use the backspace key or press Alt and turn the knob Press Alt again to return the keypad to normal mode Command DINS d i x Modify Line Modify the x value for an existing line in the Data T...

Page 347: ...ess the Data Table is turned On To select an entry in the table use the backspace key or press Alt and turn the knob Press Alt again to return the keypad to normal mode You can not delete all of the entries in the table Command DDLT d i Clear Table Clear the Data Table for the active display The table is left with a single entry for the first bin in the display Command DCLR d ...

Page 348: ...Segments in the display Choosing Edit Limits also sets this to Show Command LSON d i Limit Testing Turn Limit Testing for the active display On or Off Off turns off limit testing The limit segments are not affected On turns on limit testing Test results Pass Fail are shown in the display to the left of the graph Limit testing may not be turned on until there is at least one defined limit segment C...

Page 349: ... New Segment Add a new segment to the Limit Test for the active display The new segment starts at the end of the last existing segment This simplifies the building of a continuous limit table The new segment is also the Current Segment Command LMAX d i Limit Type Select the Limit Type for the Current Segment Upper Lower Each segment is identified by small triangular arrow markers at the segment en...

Page 350: ...nt The X coordinates are assumed to be in the display units usually Hz Use Zoom and Pan to expand the display when drawing small segments Command LSEG d i j x0 y0 x1 y1 Y0 Enter or adjust the Y coordinate for the Current Segment Start point The Y coordinates are assumed to be in the display units Use Zoom and Pan to expand the display when drawing small segments Command LSEG d i j x0 y0 x1 y1 X1 E...

Page 351: ...ent The numbering of the remaining segments may change as a result Use the Current Segment markers to identify the correct segment before editing Command LDLT d i Shift All Shift all of the Limit Segments up or down together Enter a value or use the knob to shift by 1 10 s of a division Command LSFT d x ...

Page 352: ...play The accumulation of the statistical quantities continues even when this menu is not displayed Return to this menu to see the latest statistical values When Marker Statistics are Off the various quantities are frozen New data is not included in the statistics Command MSAO d i Reset Reset and start the accumulation of marker statistics The various quantities are reset to zero and the accumulati...

Page 353: ...oes not update if Display A is not visible Command MSIA Mean Display A This menu box displays the mean value of the marker Y value for display A since Marker Stats was turned On or Reset This mean value is updated whenever new data is available for Display A and does not update if Display A is not visible Command MSEA Std Dev Display A This menu box displays the standard deviation of the marker Y ...

Page 354: ...oes not update if Display B is not visible Command MSIB Mean Display B This menu box displays the mean value of the marker Y value for display B since Marker Stats was turned On or Reset This mean value is updated whenever new data is available for Display B and does not update if Display B is not visible Command MSEB Std Dev Display B This menu box displays the standard deviation of the marker Y ...

Page 355: ...cord larger indexes are older The total number of records currently stored and available in the waterfall buffer is displayed in the Vertical Scale Bar The Start Index should not exceed the total number of records in the buffer Both displays use the same Start Index Command ESTR i Stop Index Set the stop record in the waterfall buffer for the calculation of Ln exceedance centile The analysis start...

Page 356: ...pecified by the Start and Stop index Both displays use the same Exceedance Centile Command EPCT i Calculate Excd Start the exceedance centile calculation for the active display Choose a Trace to store the result and press Enter to proceed The display must be paused or done with a 1 shot waterfall Waterfall display is not required to be on The save option must be set to Active Measurement Only The ...

Page 357: ...rameters are placed in curve Table 1 The curve in table 1 is then synthesized into whichever trace is specified by the table The non active display is taken off line and the trace with the fit data is displayed The fit parameters include the frequency scaling specified in curve table 1 For instance if the frequency scaling is set to 1000 a pole at 1 kHz will show up as a term s 1 in the pole zero ...

Page 358: ...e frequency scaling is set to 1000 the term s 1 in the curve table will produce a pole at 1 kHz in the synthesized frequency response Command ESYN i d Table Turns the curve table display on and off When the curve table display is on you can use the edit table menu to modify poles zeros residues polynomial coefficients overall gain delay or frequency scaling ...

Page 359: ...plex conjugate pair and counts as 2 poles Command ENZE i Weighting Specifies the type of weighting to use when performing the fit Auto User When Auto weighting is selected the analyzer computes an appropriate weighting function for the type of data being fit Live FFT data displays will be weighted with the Coherence funtion Live Swept Sine data are weighted with the normalized variance of channel ...

Page 360: ...display which will be fit When the Fit Setup menu is entered a band at the bottom of the graph displays the fit region The position of the band can be adjusted using the knob The width of the band can be adjusted by pressing Alt and turning the knob When the fit parameters are calculated the fit curve will be synthesized only inside the fit region Outside of the fit region the data in the fit trac...

Page 361: ... and allows the value to be changed To add a new curve paramater use the knob to move the highlighted region to the blank field at the bottom of the appropriate column in the table Pressing Edit Items allows entry of a new curve parameter in that field Command EPOL d i f g Poles Command EZER d i f g Zeros Command ERES d i f g Residues Command EPLY d i j f Polynomial Coefficient Command EGAN d f Ga...

Page 362: ...sp s Gain R s p R s p R s p m m m m Re 1 1 0 0 Command EITM i j Copy Other Table Copies the curve from the other curve fit table into the table currently being edite d Since this option will erase the curve currently being edited the analyzer will prompt for a confirmation before copying the table data Clear Table Clears all data from the curve table currently being edited Since this option will e...

Page 363: ...nd recalling displays traces and settings Remember saving to this file will write over the existing file New file names are entered using the Alt key and the letters associated with each key Press Alt again to return to normal keypad operation DOS file name conventions must be followed File names are 8 characters or less with an extension ext of up to 3 characters Default extensions are automatica...

Page 364: ...in the Current Directory If the Current File has no specified extension the default extension 78D is used The measurement frequency span averaging and window are stored with the data in order to preserve the integrity of the data when recalled Command FSAV d Disk to Display Recall data from the Current File in the Current Directory to the active display The active display will be set to Off Line w...

Page 365: ...tings become effective immediately Press Disk again to return to the main Disk menu Command SRCL i Trace to Disk Save Trace data to the Current File in the Current Directory If the Current File has no specified extension the default extension 78D is used Select a Trace 1 5 with the knob and press Enter to save it to disk Only traces which currently have data in them may be selected To save a displ...

Page 366: ...he Disk Buffers menu loads traces from disk files It also loads and saves Capture Arbitrary Source and Waterfall data buffers to disk Disk Upkeep Display the Disk Upkeep menu Press Return or Disk for the main Disk menu The Disk Upkeep menu allows files to be deleted directories to be created and removed and disks to be formatted ...

Page 367: ...ode where the stimulus is applied The name may be up to six characters long The SR780 does not use the nodal degree of freedom information itself The information is stored with the 78D file and is available for use by external programs which convert the SR780 files into formats suitable for modal analysis programs Command RFNA s Reference Number Enter the identification for the reference node For ...

Page 368: ...r use by external programs which convert the SR780 files into formats suitable for modal analysis programs Command RSNA s Response Number Enter the identification for the reference node For a frequency response function the response node is the node where the response is measured e g the node where the accelerometer or other detector is placed The number may be any integer The SR780 does not use t...

Page 369: ...85 Dynamic Signal Analyzer Abort Save Press to abort the selected disk operation while in the nodal DOF information menu Continue Save Press when finished entering nodal DOF information to continue the selected disk operation ...

Page 370: ...s and settings Remember saving to this file will write over the existing file New file names are entered using the Alt key and the letters associated with each key Press Alt again to return to normal keypad operation DOS file name conventions must be followed File names are 8 characters or less with an extension ext of up to 3 characters Default extensions are automatically supplied if no extensio...

Page 371: ...s Include the Frequency Display Setup Display Options Marker Average Window User Math Waterfall and Capture menu settings in the recall This may invalidate current Analysis menu settings Command SRCL i Sources Include the Source menu settings in the recall Command SRCL i Analysis Include the Analysis menu settings in the recall Do not recall Data Tables and Limits unless Measurements are also reca...

Page 372: ...ystem and Output menu settings in the recall Command SRCL i Macros Include stored macros in the recall Command SRCL i Recall from Disk Recall the selected instrument settings from the Current File in the Current Directory The recalled settings become effective immediately Command SRCL i ...

Page 373: ...nd settings Remember saving to this file will write over the existing file New file names are entered using the Alt key and the letters associated with each key Press Alt again to return to normal keypad operation DOS file name conventions must be followed File names are 8 characters or less with an extension ext of up to 3 characters Default extensions are automatically supplied if no extension i...

Page 374: ...s the place of the stored trace data and assumes the trace s measurement parameters Measurement Averaging Window Frequency span and length The ASCII file consists of N pairs of ASCII floating point values Each pair of values represents the real and imaginary parts of a single complex data point Thus the file contains 2N floating point numbers The values are linearly scaled usually with units of Vp...

Page 375: ...caled usually with units of Vpk The first value in the file is N 4 byte long integer followed by the real part of the first point 4 byte IEEE float then the imaginary part of the first point 4 byte IEEE float etc There are no delimiters in a binary file The data is packed Traces which are entirely real should store the value 0 0 as the imaginary part of every point The binary file has the followin...

Page 376: ...et to the length of the disk data Load A Capture Buffer A saved Arbitrary or Capture file may be loaded into a Capture buffer If the disk data has the same Capture Length and Sampling Rate as shown in the current Capture menu the data is simply loaded into the selected channel s buffer In the case of Ch1 Ch2 capture loading one channel does not disturb the contents of the other channel s buffer If...

Page 377: ...menus If the file contains records from both displays data is recalled for both displays The Waterfall Storage is set to Recalled Recalled simply means that the waterfall displays contain data which did not come from the two inputs but rather from disk Command APUT i Command CPUT i j Command WPUT Command TPUT i Buffer to Disk Save binary data from the selected data buffer to the Current File in th...

Page 378: ...le New file names are entered using the Alt key and the letters associated with each key Press Alt again to return to normal keypad operation DOS file name conventions must be followed File names are 8 characters or less with an extension ext of up to 3 characters Command DNAM s Current Directory Enter the Current Disk Directory Turning the knob will bring up the directory tree display which lists...

Page 379: ... the file and directory are correct before pressing this key Command DELF Del Cur Dir Delete the Current Directory from disk Make sure that the directory is correct before pressing this key The directory must be empty before it can be deleted Command DELD Format Floppy Format the disk The disk capacity is 720k for DS DD disks and 1 44M for DS HD disks A disk must be formatted before files can be s...

Page 380: ...he screen from any menu Command POUT Bitmap Print Prints the screen using the selected Bitmap Printer and Bitmap Area to the selected Destination Interface or Disk Other front panel operations are disabled until printing is completed Pressing backspace will abort the operation Command PRNT Vector Plot Plot the screen using the selected Vector Plotter to the selected Destination Interface or Disk O...

Page 381: ...aserJet or InkJet compatible printers HP PCL is a full page printout and HP Small PCL is half page The PCX and GIF types are bit mapped file formats Choose one of these if you want to print to a disk file and import the image into a PC application The Destination for all Bitmap Printer types can be either an on line Interface or a Disk file Command PRTP i Bitmap Area Select the portion of the scre...

Page 382: ...SCRNXXXX EXT where XXXX is a 4 digit number which automatically increments starting at the File Start Number The EXT extensions are TXT ASCII Dump EFX Epson PCL HP Laser GIF GIF PCX PCX HPG HPGL EPS Postscript Centronics selects the parallel printer interface Most dot matrix printers use this Serial selects the RS 232 serial interface Some plotters and printers use this GPIB selects the IEEE 488 i...

Page 383: ... agree with the actual address of the plotter Command PLTA i Edit A Note Select a Note to edit 0 7 and press Enter to display the Edit Note menu A Note is a text annotation within a display graph Notes are visible only within this menu and may be printed or plotted with the graph using Print Screen Press Return for the Output menu Command NOTE i j k l m s Text X Position Adjust the horizontal posi...

Page 384: ... m s File Start Number Set the Starting File Number for printing plotting or dumping to Disk XXXX up to 4 digit integer All Bitmap Printer and Vector Plotter types can save to Disk This is convenient for using a printer which is not connected to this unit or to import the screen image into a PC application Files are written to the Current Directory specified in the Disk menu Files are named SCRNXX...

Page 385: ... affect Epson FX and 24 pin and HP Laser and Laser small printer types Print Bright Select the print density of highlighted areas e g active display marker display White none on white paper 6 12 25 50 100 Black Command PBRI i Print Dim Select the print density of the normal background e g X and Y axis graph labels White none on white paper 6 12 25 50 100 Black Command PDIM i Print Black Select the...

Page 386: ...tems on the graph may be plotted using different color pens When using a single pen plotter all items are plotted using the one pen regardless of the pen definitions Only the graph display areas are plotted Plotter Text Pen Assign a plotter pen number to the text labels on the graphs 1 to 8 Command PLTX i Plotter Grid Pen Assign a plotter pen number to the graph grid 1 to 8 Command PLGD i Plotter ...

Page 387: ...gs are not changed All stored data are lost This function requires pressing the Enter key to confirm To completely reset the instrument including remote interface settings power the unit on with the backspace key held down Command RST Remote Display the System Remote interface menu Remote interface parameters should not be altered while the computer interface is active Press Return or System for t...

Page 388: ...ng enter Menu Function Control and Number keys by simply pressing the desired key these keys do not have their normal effect in this menu Use Special Keys and the knob to select Softkeys and Enter Backspace deletes the term before the cursor To edit a macro string use Macro String and the knob to move the flashing cursor within the string Delete will delete the highlighted term Menu Function Contr...

Page 389: ...key enters the Help system and displays the measurement setup and system settings Press 0 to exit Help Show Version Show the power on screen This screen shows the version number as well as the results of the power on tests The size of the installed data memory is also displayed 2 Ms 4 Ms or 8Ms ...

Page 390: ...GPIB Address Enter or adjust the instrument GPIB Address 0 30 Overide REM Select the Overide Remote mode Yes No In general every GPIB interface command will put the unit into the REMOTE state with the front panel locked out To defeat this feature set this entry to Yes In this mode the front panel is not locked out when the unit is in the REMOTE state To return from REMOTE to LOCAL front panel enab...

Page 391: ...y when testing or debugging a host program The upper half of the screen is the Receive Queue These are the most recent characters which have been received by the SR785 Commands which have already been executed are shown in normal text Commands which have not yet been executed are shown with a bright background Command errors are shown in inverse text The lower half of the screen is the Transmit Qu...

Page 392: ...e If Alarms Volume is set to Quiet alarm messages have no accompanying sound If Alarms are set to Noisy alarm messages are accompanied by an audible alarm Set system Alarms to Off for no alarm message at all Command ALRT i Done Volume If Done Volume is set to Noisy an audible alarm is sounded when a measurement is done or completed For example when linear averaging is complete an alarm is sounded ...

Page 393: ...s knob turn or interface command the screen will be blanked and random patterns displayed Press any key to return the screen to normal Command SDLY i Frequency Format Select the Frequency Format Exact Bin Rounded Exact Bin displays frequencies exactly This can make the frequency display have many more digits than required to distinguish adjacent frequency bins However this format is useful when de...

Page 394: ... on the SR785 allows enty of DOF parameters when saving data using Trace to Disk or Display to Disk When the Trace to Disk or Display to Disk is initiated using a remote command the node info prompt will not be displayed however the information entered in the Node Info menu will still be saved with the disk file as long as the Node Info Prompt softkey is on The nodal DOF information is saved with ...

Page 395: ...s minutes seconds and all entries are 6 digits 24 hour format is used Enter sets the new time or press this softkey again to abort the entry Command TIME i Date Set the System Date mm dd yy The System Date is entered as month day year and all entries are 6 digits Enter sets the new date or press this softkey again to abort the entry Command DATE i ...

Page 396: ...displayed on the test screen If the displayed characters are accurate then the keyboard interface is functioning correctly If not check that the keyboard is in the correct mode Many keyboards have a switch on the bottom to select PC XT 8088 or AT 80286 mode Turn the knob to abort this test and return to the Diagnostics menu Knob Test Display the Knob Test screen A circle with a marker is displayed...

Page 397: ...program RAM Press Return for the Memory Test menu System ROM Display the System ROM Test screen Press Begin to test the main CPU program ROM Press Return for the Memory Test menu Video RAM Display the Video Ram Test screen Press Begin to test the video display memory Press Return for the Memory Test menu Help ROM Display the Help ROM Test screen Press Begin to test the help system memory Press Ret...

Page 398: ...ternally stored serial number after replacing the DSP board The serial number which is reported on the power on screen and in the GPIB identification string is stored in the calibration ROM on the DSP board Do not use this function unless the DSP board has been replaced After replacing the DSP board use Serial Number to enter the unit serial number shown on the rear panel and use Program S N to st...

Page 399: ...eys The key deletes the term before the cursor Macro String Move the cursor to the macro string window at the top of the screen Use the knob to move the highlighted cursor within the string Delete will delete the highlighted term Menu Function Control and Number keys and Special Keys will either insert or replace at the cursor Use Insert Replace to switch between insert and replace mode Backspace ...

Page 400: ...rameter list Dec Knob Count To edit a knob event move the cursor to the macro string window at the top of the screen and move to the desired knob event displayed as Knob n Dec Knob Count will decrease the knob count by 1 which is the same as rotating counterclockwise one choice in a parameter list Delete Delete the highlighted term in a macro string To move the cursor in a macro string use Macro S...

Page 401: ...al 5 47 Marker Commands Harmonic 5 49 Marker Commands Sideband 5 50 Marker Commands Band 5 51 Marker Commands Frequency Damping 5 52 Source Commands 5 53 Sine Source Commands 5 54 Chirp Source Commands 5 55 Noise Source Commands 5 56 Arbitrary Source Commands 5 57 Swept Sine Source Commands 5 58 Input Commands 5 60 Transducer Parameter Commands 5 62 Tachometer Input Commands 5 64 Input Playback Co...

Page 402: ...settle Measurement Frequency Swept Sine Measurement Group SSTR d f 5 32 Swept Sine Start Frequency SSTP d f 5 32 Swept Sine Stop Frequency SSFR 5 32 Swept Sine Progress SRPT d i 5 32 Swept Sine Repeat Mode SSTY d i 5 32 Swept Sine Sweep Type SARS d i 5 32 Swept Sine Auto Resolution SNPS d i 5 33 Swept Sine Number of Points SSKP d i 5 33 Swept Sine Max Step Size SFST d x 5 33 Swept Sine Faster Thre...

Page 403: ... YCEN d x 5 41 Y Center Polar Y2DV d x 5 41 Y Division Polar XPAN d i 5 41 X Pan XZOM d i 5 42 X Zoom Display Options DISP d i 5 43 Display Update Mode DFMT i 5 43 Display Format ACTD i 5 43 Active Display XAXS d i 5 43 X Axis Scale Type RPMF i 5 43 RPM Frequency GRID d i 5 43 Grid On Off GDIV d i 5 43 Number of Grid Divisions GPOL d i 5 43 Nyquist Grid Type PHSL d x 5 44 Phase Suppress Threshold ...

Page 404: ...ration SDBN d i 5 50 Number of Sidebands HDSP d i 5 50 Harmonic Sideband Display HRDO d i 5 50 Harmonic Sideband Readout SPWR d i 5 50 Query the Sideband Power Band Marker BMKL d i j 5 51 Band i Left Bin j BMKR d i j 5 51 Band i Right Bin j BEXC d i 5 51 Band Exclude BRAM d i 5 51 Band Ratio Mode BPWR d i 5 51 Band Power BRAT d i 5 51 Band Ratio Frequency Damping Marker MMCA d 5 52 Frequency Dampi...

Page 405: ... 58 Swept Sine Upper Limit SSLL x 5 59 Swept Sine Lower Limit SMAX x 5 59 Swept Sine Max Level SOFF x 5 59 Swept Sine Offset Inputs ISRC i 5 60 Input Source LINK i 5 60 Analyzer Configuration I1MD i 5 60 Ch1 Input Mode I1GD i 5 60 Ch1 Input Grounding I1CP i 5 60 Ch1 Input Coupling I1RG x 5 60 Ch1 Input Range A1RG i 5 60 Ch1 AutoRange Off On I1AR i 5 60 Ch1 AutoRange Mode I1AF i 5 60 Ch1 Anti Alias...

Page 406: ...r Slope TDLA x 5 66 Trigger Delay A TDLB x 5 66 Trigger Delay B TARM 5 66 Manual Trigger Arm STMD i 5 66 Triggered Source Mode TMAN 5 66 Manual Trigger TRSR x 5 67 Starting RPM TRSM i 5 67 Start RPM Mode TRDR x 5 67 Delta RPM TRDM i 5 67 Delta RPM Mode TIAS x 5 67 Time Arm Increment Average FFT Correlation and Order FAVG d i 5 68 Average On FAVM d i 5 68 Display Average FAVT d i 5 68 Average Type ...

Page 407: ...togram User Function i USRC i x y 5 77 User Constant i Window FWIN d i 5 78 Window FWFL d i 5 78 Force Length FWTC d i 5 79 Expo TC TRWI i 5 79 Trace i to User Window WITR d i 5 79 Window to Trace i WSYM d i 5 79 Window Form Waterfall WDSP d i 5 80 Waterfall Display WSTO d i 5 80 Waterfall Storage WFSB d i 5 80 Waterfall Save Option WAVA d 5 80 Waterfall Records Stored WTOT d i 5 80 Waterfall Tota...

Page 408: ...esting On LALM d i 5 87 Limit Beep LFAL d 5 87 Limit Test Fail LCLR d 5 87 Clear Limits LMAX d i 5 87 Last Limit Segment LSEG d i j x0 y0 x1 y1 5 87 Set Limit Segment i LDLT d i 5 88 Delete Limit Segment LSFT d x 5 88 Shift Limit Segments Marker Statistics MSAO d i 5 89 Marker Statistics On MSRS 5 89 Reset Marker Statistics MSAA 5 89 Marker Max A Read MSIA 5 89 Marker Min A Read MSEA 5 89 Marker M...

Page 409: ...g FSAV d 5 94 Display to Disk FRCL d 5 95 Disk to Display SSAV 5 95 Settings to Disk SRCL i 5 95 Recall Settings TSAV i 5 96 Trace i to Disk TRCL i 5 96 Disk to Trace i DNAM s 5 96 Upkeep File Name DELF 5 96 Delete File DELD 5 96 Delete Directory Output POUT i 5 97 Print Screen hardkey PDST i 5 97 Print Plot Destination PFIL i 5 97 File Start Number DUMP 5 97 Dump Display Data PRNT 5 97 Print Scre...

Page 410: ...erence to Trace RCRF d i 5 103 Trace to Reference DUMP 5 103 Dump Display Data PRNT 5 103 Print Screen PLOT 5 103 Plot Screen ASCL d 5 103 AutoScale A1RG i 5 103 Ch1 AutoRange Off On A2RG i 5 103 Ch2 AutoRange Off On MRON d 5 103 Set Marker to Ref MKMX d 5 104 Move the Marker to the Maximum MKMN d 5 104 Move the Marker to the Minimum MKCN d 5 104 Center of FFT Span to Marker DREF d i 5 104 Display...

Page 411: ... RST 5 117 Reset IDN 5 117 Device Identification LOCL i 5 117 Local Remote OVRM i 5 117 Overide Remote Status CLS 5 120 Clear All Status Registers PSC i 5 120 Power On Status Clear SRE i j 5 120 Serial Poll Status Enable STB i 5 120 Serial Poll Status Read ESE i j 5 120 Standard Event Status Enable ESR i 5 121 Standard Event Status Read ERRE i j 5 121 Error Status Enable ERRS i 5 121 Error Status ...

Page 412: ...ad Arbitrary Binary ALRM i 5 100 Alarms On ALRT i 5 100 Alarms Volume AOVL i 5 100 Audible Overload APUT i 5 113 Download Arbitrary Buffer ARAT i 5 57 Arbitrary Source Rate ASCL d 5 103 AutoScale ASRC i 5 57 Arbitrary Source Buffer ASTR i 5 57 Arbitrary Source Start B BEXC d i 5 51 Band Exclude BMKL d i j 5 51 Band i Left Bin j BMKR d i j 5 51 Band i Right Bin j BPWR d i 5 51 Band Power BRAM d i 5...

Page 413: ... Table Query DUMP 5 103 Dump Display Data DUMP 5 97 Dump Display Data E EDLY i x 5 91 Table Delay EFIT d 5 91 Start Fit EFSC i x 5 91 Table Frequency Scale EGAN i x 5 92 Table Gain ETRC i j 5 92 Table Item Query ENPL i 5 91 Number Poles ENZE i 5 91 Number Zeros EPCT i 5 90 Exceed Centile EPLY i j k x 5 92 Polynomials EPOL i j x y 5 92 Poles ERES i j x y 5 92 Residues ERNG d i j 5 91 Fit Range ERRE...

Page 414: ...5 95 Reset Disk Catalog FSAV d 5 94 Display to Disk FSPN d f 5 28 FFT Frequency Span FSPN d i 5 28 Sampling Time FSTR d f 5 28 FFT Start Frequency FWFL d i 5 78 Force Length FWIN d i 5 78 Window FWTC d i 5 79 Expo TC FXST s 5 94 File Exist G GDIV d i 5 43 Number of Grid Divisions GPOL d i 5 43 Nyquist Grid Type GRID d i 5 43 Grid On Off H HBIN d i 5 36 Histogram Bins HDSP d i 5 50 Harmonic Sideban...

Page 415: ... KNOB i 5 106 Knob L LALM d i 5 87 Limit Beep LCLR d 5 87 Clear Limits LDLT d i 5 88 Delete Limit Segment LFAL d 5 87 Limit Test Fail LINK i 5 60 Analyzer Configuration LMAX d i 5 87 Last Limit Segment LOCL i 5 117 Local Remote LSEG d i j x0 y0 x1 y1 5 87 Set Limit Segment i LSFT d x 5 88 Shift Limit Segments LSON d i 5 87 Show Limit Segments LTST d i 5 87 Limit Testing On M MALC i j k 5 84 Alloca...

Page 416: ...N NAMP x 5 56 Noise Amplitude NAVG d 5 68 Averages Completed NAVG d 5 71 Octave Averages Completed NBUR x 5 56 Noise Burst Percentage NOTE i j k l m s 5 99 Display Note NPER x 5 56 Noise Source Period NTYP i 5 56 Noise Type O O1BN d i 5 35 Track 1 BNC O1TK d f 5 35 Track 1 Order O2BN d i 5 35 Track 2 BNC O2TK d f 5 35 Track 2 Order OCHN d i 5 30 Octave Channels OCNF d i 5 71 Octave Confidence Leve...

Page 417: ... 5 97 Print Screen hardkey PRNT 5 103 Print Screen PRNT 5 97 Print Screen PRTP i 5 97 Bitmap Printer Type PSCR i 5 97 Bitmap Area PSDU d i 5 40 PSD Units On Off R RCRF d i 5 103 Trace to Reference RCTR d i 5 103 Trace i to Display d REFY d j 5 107 Read Ref Display d bin j RFDR i 5 118 Reference Node Direction RFNA s 5 118 Reference Node Name RFNU i 5 118 Reference Node Number RPMF i 5 43 RPM Frequ...

Page 418: ...hold SSRF x 5 58 Swept Sine Ideal Reference SSTM d x 5 73 Swept Sine Settle Time SSTP d f 5 32 Swept Sine Stop Frequency SSTR d f 5 32 Swept Sine Start Frequency SSTY d i 5 32 Swept Sine Sweep Type SSUL x 5 58 Swept Sine Upper Limit STMD i 5 66 Triggered Source Mode STRT 5 102 Start Reset STYP i 5 53 Source Type SVNI i 5 118 Save Nodal Information SVRF d i 5 103 Reference to Trace SVTR d i 5 102 D...

Page 419: ... l 5 74 Correlation User Function i USRS i j k l 5 74 Swept Sine User Function i USRT i j k l 5 74 Order User Function i V VIEW d i 5 39 Display View W WANG d i 5 81 Waterfall Angle WAVA d 5 80 Waterfall Records Stored WDSP d i 5 80 Waterfall Display WFSB d i 5 80 Waterfall Save Option WFSK d i 5 80 Waterfall FFT Skip WFST d i 5 81 Waterfall Fast Angles WGET 5 114 Upload Waterfall Buffer WGET 5 11...

Page 420: ...EN d x 5 41 X Center Polar XDIV d x 5 41 X Division Polar XPAN d i 5 41 X Pan XZOM d i 5 42 X Zoom Y Y2DV d x 5 41 Y Division Polar YCEN d x 5 41 Y Center Polar YDIV d x 5 41 Y Division YMAX d x 5 40 Y Maximum YMDX d x y 5 41 Ymax Y Division YMID d x 5 40 Y Midpoint YMIN d x 5 41 Y Minimum ...

Page 421: ... an input that is used to control the SR785 s data transmission If desired the handshake pins may be ignored and a simple 3 wire interface pins 2 3 and 7 may be used The RS232 interface Baud Rate Word Length and Parity must be set in the System Remote menu Screen Indicators And Queues To assist in programming the SR785 has 4 interface indicators which are displayed at the top of the screen The RS2...

Page 422: ...re cleared and an error reported The present value of a particular parameter may be determined by querying the SR785 for its value A query is formed by appending a question mark to the command mnemonic and omitting the desired parameter from the command Values returned by the SR785 are sent as a string of ASCII characters terminated by a carriage return cr on RS232 and by a line feed lf on GPIB If...

Page 423: ...n finished The Disk Error bit may be checked to make sure that the FSAV Display to Disk command completed without error Since the FSAV command may take a long time to execute it is important that the host computer interface does not time out while waiting for the response to the ERRS query In the case where the host interface times out before the ERRS response the host program must wait before sen...

Page 424: ...ands which perform menu softkey functions are not allowed unless the corresponding softkey function is allowed If the softkey is not available in the current context either shown in gray or not displayed at all then the corresponding set command is not allowed In general softkeys are disabled for two reasons the function is specifically not allowed in the current measurement context or the functio...

Page 425: ...ters Values are returned as a string of ASCII characters unless otherwise noted Do NOT send or as part of the command For example the command sequence FSTR d f is used as follows FSTR 0 1 024E3 Set the Start Frequency of DispA to 1024 Hz FSTR 0 Query the Start Frequency of DispA Variables are defined as follows d display 0 DispA 1 DispB 2 Both Displays d 2 is not allowed for queries i j k l m inte...

Page 426: ...fault units are also the units used when the analyzer responds to queries Some commands must identify the units in which queries are responded to Examples would be the source amplitude and input range commands which can return values in dB and linear units In these cases the response to the query is in the form f j where f is the actual floating point return value and j is the index into the list ...

Page 427: ...o not apply to interface commands Analyzer Configuration and Linking When the Analyzer Configuration is set to Dual Channel many commands that have a d display parameter require d be set to 2 both channels This reflects the fact that the two displays cannot have different frequency parameters in the dual channel configuration Command Context Errors Commands which perform softkey functions are not ...

Page 428: ...cy of display d The parameter i selects 100 0 kHz 0 or 102 4 kHz 1 To set the Base Frequency d must be 2 both displays There is only one Base Frequency for both displays Changing the Base Frequency will affect all of the FFT and source frequency parameters This command is valid only when the Measurement Group is FFT Correlation or Time Histogram The set command requires at least one display to be ...

Page 429: ...es display d to be Live Since correlation is always a baseband measurement this command is not valid when the measurement group is correlation UNST d The UNST command unsettles the measurement of display d The measurement is not actually perturbed by the UNST command The settling status is set to unsettled and the full settling time of the measurement is required before the status returns to settl...

Page 430: ...ES command sets queries the Octave Resolution of display d The parameter i selects 1 1 0 1 3 1 or 1 12 2 octave analysis Changing the resolution may change the values of the Highest and Lowest Band for display d For 1 Channel octave analysis the set command requires d 2 This command is valid only when the Measurement Group is Octave The set command requires display d to be Live OCHN d i The OCHN c...

Page 431: ...85 Dynamic Signal Analyzer a way as to require the measurement to settle it is convenient to use the UNST command and wait for settling to finish This command is valid only when the Measurement Group is FFT Correlation or Octave ...

Page 432: ... measured While a sweep is in progress SSFR returns values from 0 to the Number Of Points 1 After a sweep is started SSFR will not return 0 until the first point is measured This may take some time if Source Ramping is On or if the Settling Time is very long This command is valid only when the Measurement Group is Swept Sine SRPT d i The SRPT command sets queries the swept sine Repeat Mode of disp...

Page 433: ... a maximum number of skips from 2 to 200 The set command requires d 2 both displays This command is valid only when the Measurement Group is Swept Sine The set command requires a display to be Live SFST d x The SFST command sets queries the swept sine Faster Threshold of display d The parameter x is a level from 0 01 to 3 0 dB The set command requires d 2 both displays This command is valid only w...

Page 434: ...ires d 2 both displays This command is valid only when the Measurement Group is Order The set command requires a display to be live ODLT d x The ODLT command sets queries delta order for display d The parameter x is delta order a real number The range of f is between Max Order 400 and 1 The set command requires d 2 both displays This command is valid only when the Measurement Group is Order The se...

Page 435: ...d with the track 1 measurement for display d The parameter i sets the input channel to Channel One 0 or Channel 2 1 The set command requires d 2 both displays This command is valid only when the Measurement Group is Order The set command requires a display to be Live O2TK d x The O2TK command sets queries the order associated with the track 2 measurement for display d The parameter x is the order ...

Page 436: ... Group is Time Histogram The set command requires the display d to be Live HBIN d i The HBIN command sets queries the number of histogram bins for display d The parameter i is related to the number of histogram bins by the equation Bins 2 i 2 The range of i is from 0 to 8 This command is valid only when the Measurement Group is Time Histogram The set command requires the display d to be Live FBAS ...

Page 437: ...e new group The set command requires d 2 both displays MEAS d i The MEAS command sets queries the Measurement of display d The parameter i selects the measurement from the list below Only those measurements available in the current Measurement Group are allowed Each measurement has an associated view Changing the Measurement changes the View to the view last used with the new Measurement The set c...

Page 438: ...urement 33 Octave 1 34 Octave 2 35 Capture 1 36 Capture 2 37 Octave User Function 1 38 Octave User Function 2 39 Octave User Function 3 40 Octave User Function 4 41 Octave User Function 5 Swept Sine Group i Measurement 42 Spectrum 1 43 Spectrum 2 44 Normalized Variance 1 45 Normalized Variance 2 46 Cross Spectrum 47 Frequency Response 48 Swept Sine User Function 1 49 Swept Sine User Function 2 50 ...

Page 439: ... 2 78 Time 1 79 Time 2 80 Capture Buffer 1 81 Capture Buffer 2 82 Histogram User Function 1 83 Histogram User Function 2 84 Histogram User Function 3 85 Histogram User Function 4 86 Histogram User Function 5 A measurement should be setup by first choosing the Measurement Group then the Measurement then the View then the Units Finally the display scale and references should be set VIEW d i The VIEW...

Page 440: ...the pk units setting for display d The parameter i sets pkUnits to Off 0 pk 1 rms 2 and pp 3 PSDU d i The UNPK command sets queries psd units setting for display d The parameter i sets psd Units to Off 0 or On 1 UNPH d i The UNPH command sets queries phase units setting for display d The parameter i sets phase Units to Degrees 0 or Radians 1 DBMR x The DBMR command sets queries the dBm Reference I...

Page 441: ... in the display units This command is only valid when the View is Nichols or Nyquist XDIV d x The XDIV command sets queries the polar X Division scale of display d The parameter x is a real number in the display units This command is only valid when the View is Nichols or Nyquist Changing the scale of a display may change the X Center value Always use the XCEN command after the XDIV command YCEN d...

Page 442: ...namic Signal Analyzer XZOM d i The XZOM command sets queries the Zoom factor X axis expand of display d The parameter i is the zoom factor 1 5 This command is not valid when the X axis is logarithmic or when the View is Nyquist or Nichols ...

Page 443: ...XAXS command sets queries the X Axis Scale Type of display d The parameter i selects Linear 0 or Logarithmic 1 This command is valid only when display d is an FFT measurement with frequency as the X axis FFT measurements with a time X axis Time WinTime Capture or User Time Function always have a linear scale RPMF i The RPMF command sets queries the RPM frequency scaling for both displays The param...

Page 444: ...d of display d The parameter x is a real magnitude squared value This affects the calculation of phase for display d DDXW d x The DDXW command sets queries the d dx Window of display d The parameter x is a percentage of the display width This affects the calculation of d dx and group delay for user math functions in display d ...

Page 445: ...r region will be centered on bin i if possible The Normal marker will still seek the Max Min or Mean within the region This command is not valid if the Marker of display d is Off MWFL d i The MWFL command moves the Waterfall Marker of display d to record i in the Z axis Record 0 is the most recent record in the display The marker of each display must be moved separately d 2 is not allowed This com...

Page 446: ...terfall MRKZ queries the Z axis record number of the marker Lower record numbers are more recent This command is not valid if the Marker of display d is Off MKMX d The MKMX command performs Marker to Max on display d Same as Marker Max key The marker of each display must be moved separately d 2 is not allowed This command is not valid if the Marker of display d is Off MKMN d The MKMN command perfo...

Page 447: ... command sets queries the X Offset for the Normal Marker of display d The parameter x is a real number in display units This command is only valid if the Marker Mode for display d is Normal MROY d x The MROY command sets queries the Y Offset for the Normal Marker of display d The parameter x is a real number in display units This command is only valid if the Marker Mode for display d is Normal MXR...

Page 448: ...Analyzer If Marker Rel is Relative to Offset MRON d sets the Marker Rel to Off absolute marker readings MRON d returns 0 if Marker Rel is Off and 1 if Marker is Rel to Offset This command is only valid if the Marker Mode for display d is Normal ...

Page 449: ...r minus the Number of Sidebands i 0 is valid only for Sideband marker This command is only valid if the Marker Mode for display d is Harmonic or Sideband HRDO d i The HRDO command sets queries the Harmonic and Sideband Marker Readout for display d The parameter i selects Absolute 0 or Relative to Fundamental 1 This command is only valid if the Marker Mode for display d is Harmonic or Sideband HTHD...

Page 450: ...display d For Sideband Marker i 0 selects the Fundamental i 1 selects the first lower sideband i 1 selects the first upper sideband The maximum value of i plus or minus the Number of Sidebands i 0 is valid only for Sideband marker This command is only valid if the Marker Mode for display d is Harmonic or Sideband HRDO d i The HRDO command sets queries the Harmonic and Sideband Marker Readout for d...

Page 451: ...nly valid if the Marker Mode for display d is Band BEXC d i The BEXC command queries the Band Exclusion for display d The parameter i selects none 0 1from2 1 or 2from1 2 This command is only valid if the Marker Mode for display d is Band BRAM d i The BRAM command queries the Band Ratio Mode for display d The parameter i selects 2 1 0 or 2 1 2 1 This command is only valid if the Marker Mode for dis...

Page 452: ...equency Damping MMCA d The MMCA command queries the Frequency Damping marker result The query returns two values in the form f g where f is the resonant frequency and g is the damping factor This command is only valid if the Marker Mode for display d is Frequency Damping ...

Page 453: ... The parameter i selects Off 0 or On 1 This command is not valid when the Measurement Group is Swept Sine STYP i The STYP command sets queries the Source Type The parameter i selects Sine 0 Chirp 1 Noise 2 or Arbitrary 3 When the Measurement Group is Swept Sine the Source Type may not be changed and this command is not valid ...

Page 454: ...V The SOFF command sets queries the Offset of the Sine Source The parameter x is a real number of the specified units The query returns two numbers of the form y i where y is a real number and i is an index indicating the units This command is valid only when the Source Type is Sine S2FR f kHz Hz mHz µ µ µ µHz The S2FR command sets queries the Frequency of Sine Tone 2 The parameter f is a frequenc...

Page 455: ...he units This command is valid only when the Source Type is Chirp CBUR x The CBUR command sets queries the Chirp Burst Percentage The parameter x is a percentage from 1 to 100 This command is valid only when the Source Type is Chirp and the Measurement Group is FFT or Correlation CSRC i The CSRC command sets queries the Source Display The parameter i selects DisplayA 0 or DisplayB 1 This command i...

Page 456: ...nd is valid only when the Source Type is Noise NBUR x The NBUR command sets queries the Noise Burst Percentage The parameter x is a percentage from 1 to 100 This command is valid only when the Source Type is Noise and the Measurement Group is FFT or Time Histogram NPER x ks s ms The NPER command sets queries the Noise Burst Source Period The parameter x is a time from 4 ms to 1 ks This command is ...

Page 457: ...st contain data otherwise an error occurs This command is valid only when the Source Type is Arbitrary ASTR i The ASTR command sets queries the Arbitrary Source Start point The parameter i is a point in the Arbitrary Waveform either in Arbitrary memory or a Capture buffer This command is valid only when the Source Type is Arbitrary ALEN i The ALEN command sets queries the Arbitrary Source Length T...

Page 458: ... Reference The parameter x is the ideal reference in the specified units The query returns two numbers of the form y i where y is a real number and i is an index indicating the units This command is valid only when the Measurement Group is Swept Sine and Auto Level Reference is Ch1 or Ch2 SRMP i The SRMP command sets queries the Swept Sine Source Ramping The parameter i selects Off 0 or On 1 This ...

Page 459: ...ameter x is the maximum level in the specified units The query returns two numbers of the form y i where y is a real number and i is an index indicating the units This command is valid only when the Measurement Group is Swept Sine and Auto Level Reference is Ch1 or Ch2 SOFF x mV V The SOFF command sets queries the Offset of the Swept Sine Source The parameter x is a real number of the specified un...

Page 460: ...Vpp dBVrms Vpk Vpp Vrms dBEUpk dBEUpp dBEUrms EUpk EUpp EUrms The I1RG command sets queries the Ch1 Input Range The parameter x is the full scale input range in the specified untis If the exact input range specfied is not available the closest available input range will be used The query command returns a value of the form x j where x is the value and j is the index into the list of units If Ch1 A...

Page 461: ... specfied is not available the closest available input range will be used The query command returns a value of the form x j where x is the value and j is the index into the list of units If Ch2 AutoRange is On the I2RG i command will turn Ch2 AutoRange Off and the set the Ch2 Range to f I2AR i The I2AR command sets queries the Ch2 AutoRange Mode The parameter i selects Normal 0 or Tracking 1 A2RG ...

Page 462: ...9 lbs 2 m 10 N 3 in s2 11 dyne 4 in s 12 Pas 5 in 13 bar 6 mil 14 USER 7 g EU1V d x The EU1V command sets queries the Ch1 Engineering Units per Volt scale for display d The set command requires d 2 both displays The parameter x is real number of EU Volt EU s per Volt EU1U d s The EU1U command sets queries the Ch1 User Label for display d The set command requires d 2 both displays The string s is t...

Page 463: ...3 in s2 11 dyne 4 in s 12 Pas 5 in 13 bar 6 mil 14 USER 7 g EU2V d x The EU2V command sets queries the Ch2 Engineering Units per Volt scale for display d The set command requires d 2 both displays The parameter x is real number of EU Volt EU s per Volt EU2U d s The EU2U command sets queries the Ch2 User Label for display d The set command requires d 2 both displays The string s is the user label T...

Page 464: ... TALV command sets queries the Tachometer Trigger Level The parameter x is the tach trigger level in volts TASL i The TARG command sets queries the Tachometer Trigger Slope The parameter i selects Rising 0 or Falling 1 TAHO i The TAHO command sets queries the Tachometer Holdoff Enable The parameter i selects Off 0 or On 1 TAHD x The TAHD command sets queries the Tachometer Holdoff Time The paramet...

Page 465: ...parameter i is the length in kPts in the Capture buffer i must be an even number from 2 to the length of the waveform This command is valid only when the Input Source is Playback IMOD i The IMOD command sets queries the Capture Playback Mode The parameter i selects 1 Shot 0 or Circular 1 This command is valid only when the Input Source is Playback ISPD i The ISPD command sets queries the Capture P...

Page 466: ...are turned on for the active display otherwise ChU are equivalent to Volts TSLP i The TSRC command sets queries the Trigger Slope The parameter i selects Rising 0 or Falling 1 TDLA x s ms µ µ µ µs The TDLA command sets queries the Trigger Delay 1 The parameter x is the delay in the specified units This command is valid only when the Measurement Group is FFT or Correlation TDLB x s ms µ µ µ µs The ...

Page 467: ...t RPM mode The parameter i selects Start RPM Off 0 or On 1 TRDR x The TRDR command sets queries the RPM Arming Delta RPM The parameter x is delta rpm TRDM i The TRDM command sets queries the RPM Arming Delta RPM sense The parameter i selects Absolute Change 0 Increasing RPM 1 or Decreasing RPM 2 TIAS x The TIAS command sets queries the Time Arming Step The parameter x is the time increment in seco...

Page 468: ...lid only when the Measurement Group is FFT Correlation or Order The set command requires display d to be Live FAVN d i The FAVN command sets queries the Number of Averages for display d The parameter i is a number of averages from 2 to 32767 This command is valid only when the Measurement Group is FFT Correlation or Order The set command requires display d to be Live NAVG d The NAVG command querie...

Page 469: ...conds The set command requires d 2 both displays This command is valid only when the Measurement Group is FFT The set command requires a display to be Live PAVA The PAVA command accepts the previewed time record The averages of both displays is updated to include the previewed time record Poll the NEWA and NEWB New Data status bits in the Display Status word to determine when each time record has ...

Page 470: ...This change does not set NEWA or NEWB but occurs upon receipt of the accept or reject command or after a Preview Time This command is valid only when the Measurement Group is FFT This command has no effect unless the previewed time records are displayed ...

Page 471: ...ompleted for display d The returned value is the amount of averaging completed in 4 ms increments For example a completed linear average of 1 second returns 250 For exponential averaging the returned value is the actual averaging completed and eventually exceeds the Octave Average Time This command is valid in FFT and Octave Measurement Group OCNF d i The OCNF command sets queries the Octave Avera...

Page 472: ...p is Octave The set command requires display d to be Live OLAT d i The OLAT command sets queries the Octave Linear Average Mode for display d The parameter i selects Triggered 0 or Continuous 1 The set command requires d 2 both displays have the same mode This command is valid only when the Measurement Group is Octave The set command requires a display to be Live ...

Page 473: ... d 2 both displays This command is valid only when the Measurement Group is Swept Sine The set command requires a display to be Live SITM d x ks s ms The SITM command sets queries the Swept Sine Integration Time for display d The parameter x is an integration time from 0 016 to 1000 seconds The set command requires d 2 both displays This command is valid only when the Measurement Group is Swept Si...

Page 474: ... C O and S Or and H indicate in which measurement groups each token is valid FFT Correlation Octave Swept Sine Order and Histogram For example to define FFT User Function 3 as FFT 1 FFT 2 the command USRF 3 10 1 20 is used If the function cannot be entered a command execution error occurs Operand Operation Token Valid in Groups Mag 101 F C O S Or H Conj 102 F C O S Or H Real 103 F C O S Or H Imag ...

Page 475: ...6 F C O S Or H 7 F C O S Or H FFT Group Operands Time 1 20 Time 2 21 FFT 1 22 FFT 2 23 Pwr 1 14 Pwr 2 15 Coherence 70 CrossSpec 71 Freq Resp 72 Vec F1 24 Vec F2 25 RMS F1 26 RMS F2 27 PeakHold F1 28 PeakHold F2 29 RMS CrossSpec 67 Correlation Group Operands Time 1 20 Time 2 21 Auto_Corr 1 64 Auto_Corr 2 65 X_Corr 73 ...

Page 476: ...ct 2 37 Swept Sine Operands Spec 1 38 Spec 2 39 Norm Var 1 40 Norm Var 2 41 Cross Spectrum 74 Freq Resp 75 Order Operands Time 1 42 Time 2 43 Spec 1 60 Spec 2 61 Pwr 1 62 Pwr 2 63 Vec Time 1 44 Vec Time 2 45 Time Histogram Operands Histo 1 48 Histo 2 49 PDF 1 50 PDF 2 51 CDF 1 52 CDF 2 53 Time 1 20 Time 2 21 Operands for All Groups Trace1 1 Trace2 2 Trace3 3 Trace4 4 Trace5 5 Const1 6 ...

Page 477: ...t2 7 Const3 8 Const4 9 Const5 10 j 11 USRC i x y The USRC command sets queries the real and imaginary parts of User Constant i The parameter i selects a User Constant from 1 to 5 The parameters x and y are floating point values for the real and imaginary parts ...

Page 478: ... the window which will be applied to the measurement in Display A The parameter i selects Force Window 0 or Exponential Window 1 This command is valid only when the Measurement Group is FFT or Order The set command requires display d to be Live and the Force Exponential Window to be selected W2FE i The W2FE command sets queries the window which will be applied to Channel 2 when the main window sel...

Page 479: ...d to be Live and the Force Exponential window to be selected TRWI i The TRWI command copies the real part of stored Trace i to the User window Trace i must contain stored data This command is valid only when the Measurement Group is FFT or Order WITR d i The WITR copies the window of display d to the real part of Trace i Trace i will have a length of 2048 points This command is valid only when the...

Page 480: ...pt Sine WTOT d i The WTOT command sets queries the Waterfall Total Count for display d The parameter i is a number of records If the allocated memory is too small for the requested number of records an error occurs This command is not valid when the Measurement Group is Swept Sine WAVA d The WAVA command queries the number of records available in the waterfall buffer for display d Records are not ...

Page 481: ...Measurement Group is Swept Sine WFST d i The WFST command sets queries the Waterfall Fast Angles for display d The parameter i selects Off 0 or On This command is not valid when the Measurement Group is Swept Sine WTHR d i The WTHR command sets queries the Waterfall Threshold for display d The parameter i is a percentage of the full scale trace height This command is not valid when the Measurement...

Page 482: ...h waterfall storage on If there is no record j then an error occurs WSLC d i j The WSLC command saves the waterfall time slice of bin j 0 is left most on x axis from display d to Trace i 1 5 This command is valid only when the measurement is paused with waterfall storage on If there is no bin j then an error occurs ...

Page 483: ...om 2 to the maximum allocated memory This command is invalid it the source is arbitrary playback from the capture buffer or if the measurement group is Swept Sine CRAT i The CRAT command sets queries the Capture Rate The parameter i 0 19 selects a rate equal to the maximum rate divided by 2 to the ith power Thus i 0 selects the maximum rate and i 1 selects half the maximum rate This command is inv...

Page 484: ...er Track and Arbitrary Waveform MMEM returns the total number of memory blocks 2 kPts block in the instrument MALC i j k The MALC command sets the Memory Allocation to i blocks for Capture j blocks for Waterfall Order Track and k blocks for Arbitrary Waveform The sum of i j k cannot exceed the Total Available Memory The MALC command automatically confirms the allocation ...

Page 485: ...ve display Use the ACTD command to select the active display Only the Data Table of the active display may be edited or queried DINS d i j The DINS command sets queries the X Axis bin number for line number i in the Data Table for display d The parameter i selects the line number If the value of i is greater than the last line number an error is returned The parameter j is the X axis bin number of...

Page 486: ...for display d The DTRD d command queries the entire table The data is returned in the form X0 Y0 X1 Y1 X2 Y2 Xn Yn lf where Xn Yn are the last entries in the table index n Any table entry not within the current measurement span returns the value 1 0E 34 for both X and Y The DTRD d i command queries the X and Y values for line i only The data is returned X Y lf If the table entry is not within the ...

Page 487: ...ments Limit segments may not be defined or edited after the Measurement or Measurement Group is changed until LCLR clears the existing segments LMAX d i The LMAX command sets queries the Last Limit Segment Number for display d The parameter i is a last limit segment number from 0 to 199 The set command is not valid for d 2 both displays The LMAX command queries the last limit segment number The LM...

Page 488: ...lf The LSEG d i j x0 y0 x1 y1 command sets the endpoints of segment i to x0 y0 and x1 y1 and the type to Upper j 0 or Lower j 1 This command also sets Limit Segments to Show LDLT d i The LDLT command deletes Limit Segment Number i for display d The value of i may not exceed the last limit segment number The remaining segments are renumbered sequentially This command is not valid for d 2 both displ...

Page 489: ...displayed MSRS The MSRS command resets and starts the accumulation of marker statistics The various quantities are reset to zero and the accumulation of marker statistics begins MSAA The MSAA command queries Max for the Display A Marker MSIA The MSIA command queries Min for the Display A Marker MSEA The MSEA command queries Mean for the Display A Marker MSSA The MSSA command queries Standard Devia...

Page 490: ...of records stored in the waterfall buffer minus one This command is not valid when the measurement group is swept sine EPCT i The EPCT command sets queries the Exceedance Centile for both displays The parameter i is a centile from 1 to 99 This command is not valid when the measurement group is swept sine EXCE d i The EXCE command starts the exceedance centile calculation for display d The paramete...

Page 491: ...umber of zeros in the fitting function The parameter j is the number of zeros between 0 and 20 EWTU j The EWTU command sets queries the type of weighting used for fitting The parameter j specifies Uniform 0 Coherence 1 or User 2 EWTT j The EWTT command sets queries the trace which will be used if user weighting is selected The parameter j is the trace number 1 5 ERNG d i j The ERNG command sets qu...

Page 492: ...r k selects which polynomial coeffiecient will be set queried from 0 up to the number of items in the list The parameter x is the actual coefficient This command will change the specified table format to polynomial EPOL i j x y The EPOL command sets queries the poles for one of the curve tables The parameter i selects curve table 1 0 or curve table 2 1 The parameter j selects which pole will be se...

Page 493: ...e real part of the residue The optional parameter y is the imaginary part if any of the residue This command will change the specified table format to pole residue ECLR i The ECLR command clears one of the curve tables The parameter i selects curve table 1 0 or curve table 2 1 ...

Page 494: ...E looks within the current directory for a sub directory called DIRNAME If it exists the current directory is changed to DIRNAME FDIR moves down a directory path one level at a time Use multiple FDIR commands to move down a directory path FDIR moves up one directory towards the root FDIR sets the current directory to the root Only the last directory in the path is displayed in the menu box MDIR s ...

Page 495: ...ves display d data to disk The file name is specified by FNAM and the directory is specified by FDIR FRCL d The FRCL command recalls data from disk to display d Display d will be set Off Line The file name is specified by FNAM and the directory is specified by FDIR SSAV The SSAV command saves the instrument settings to disk The file name is specified by FNAM and the directory is specified by FDIR ...

Page 496: ...MYDATA DAT command sets the file name to MYDATA DAT DOS file name conventions must be followed i e file names are 8 characters or less with an optional extension of up to 3 characters The extension is NOT automatically supplied File access is to the current directory DELF The DELF command deletes the file specified by the Upkeep File Name from the current directory The file name is specified by DN...

Page 497: ...DUMP command dumps the data in the active display in ASCII format to the selected Destination Interface or Disk The data is written f y x cr with the data for each point on a single line f is the frequency or time value y is the y axis value and x is the x axis value if necessary PRNT The PRNT command prints the screen using the selected Bitmap Printer type and Destination All other operations are...

Page 498: ... other operations are disabled until plotting is completed PLTP i The PLTP command sets queries the Vector Plotter type The parameter i selects HPGL 0 or PostScript 1 PLTA i The PLTA command sets queries the Plotter GPIB Address The parameter i ranges from 0 to 30 and should agree with the address of the plotter in use PCIC i The PCIC command sets queries the GPIB Control mode The parameter i sele...

Page 499: ... from 0 to 9 The parameter j makes the note Not Visible 0 or Visible 1 To turn a Note On and Off use the NOTE i j command The parameter k puts the note in Display A 0 or Display B 1 The parameters l and m are the Text X and Text Y position from 0 to 100 The string s is the note text The parameters k l m and s must always be sent together ...

Page 500: ...ects Off 0 or On 1 ALRM i The ALRM command sets queries the Alarms Off On The parameter i selects Off 0 or On 1 ALRT i The ALRT command sets queries the Alarms Volume The parameter i selects Quiet 0 or Noisy 1 ADON i The ADON command sets queries the Done Volume The parameter i selects Quiet 0 or Noisy 1 AOVL i The AOVL command sets queries the Audible Overload The parameter i selects Off 0 or On ...

Page 501: ... the time to i 0 23 hours j 0 59 minutes and k 0 59 seconds The parameters i j and k must all be sent DATE i j k The DATE command sets queries the System Date The DATE command queries the date A string of the form MM DD YY is returned The DATE i j k command sets the date to i 1 12 month j 1 31 day and k 0 99 year The parameters i j and k must all be sent ...

Page 502: ...ause Cont key CONT If the measurement is paused CONT continues the measurement If the measurement is running CONT has no effect This function is similar to pressing the Pause Cont key UNST d The UNST command unsettles the measurement of display d The measurement is not actually perturbed by the UNST command The settling status is set to unsettled and the full settling time of the measurement is re...

Page 503: ...data in the active display in ASCII format to the selected Destination Interface or Disk The data is written f y x cr with the data for each point on a single line f is the frequency or time value y is the y axis value and x is the x axis value if necessary ASCL d The ASCL command AutoScales display d This is the same as pressing the Auto Scale A or Auto Scale B keys The displays are AutoScaled se...

Page 504: ...d is not valid if the Marker of display d is Off DREF d i The DREF command sets and clears the Display Reference for display d If i is 0 the Display Reference is turned Off If i is 1 the current data becomes the Display Reference and the Display Reference is turned On DREF d 1 only sets the Display Reference if the Display Reference is currently off This is similar to the Display Ref key SNAP d Th...

Page 505: ...y 10 bottom 40 Freq 33 Display Setup 34 Display Options 35 Marker 36 Source 41 Input 42 Trigger 43 Average 44 User Math 49 Window 50 Waterfall 51 Capture 52 Analysis 57 Disk 58 Output 59 System 60 AutoScale A 37 AutoScale B 45 Span Up 53 Span Down 61 AutoRange Ch1 38 AutoRange Ch2 46 Marker Max 54 Marker Min 62 Marker Ref 39 Display Ref 47 Marker Center 55 Show Setup 63 Start Reset 17 Pause Cont 2...

Page 506: ...selects counter clockwise 0 or clockwise 1 TONE i j The TONE command makes an audible tone The parameter i is the duration in 5 ms increments and j selects a note from 0 to 66 Sequential TONE commands need to be separated by a pause which is at least as long as the preceding tone PLAY i The PLAY command plays one of the SR785 s pre programmed sounds The parameter i selects a sound from 0 to 6 most...

Page 507: ...tarting with bin 0 and ending with bin length 1 The data points are ASCII real numbers separated by commas and the last data point is followed by a terminator If the DSPY d command is used with the RS232 interface the host computer interface must be fast enough to keep up with the data stream The DSPY command returns data from the last available display update To keep the data static pause the mea...

Page 508: ... separation between data points No line feed follows the last data point instead EOI is asserted with the last byte The 4 bytes are an IEEE floating point number The returned data depends upon the display View and Units The data values are the same as if they were read with the marker In the case of a 2 D view Nyquist or Nichols two values per bin are returned 8 bytes per bin The first value is th...

Page 509: ...of showing the actual complex data A trace contains n complex points The value of n depends upon the type and length of the target trace N should be chosen equal to or less than the length of the target trace If the length is less than that of the target trace the remainder of the trace will be filled with zeros The download sequence is as follows Host Send TLOD i n Do NOT wait for IFC to be set i...

Page 510: ...e same units as the target trace Depending upon the trace measurement the values are assumed to be either unitless Volts or Volts2 See TLOD for more The download sequence is as follows Host Send TASC i n Do NOT wait for IFC to be set in the Serial Poll status SR785 Checks to make sure that Trace i has length n Returns 1 4 byte binary long int if OK to begin data transfer A return of 0 indicates th...

Page 511: ...rial Poll status before sending another command TGET i The TGET command uploads a Trace buffer to the host computer This command is valid only via the GPIB interface The parameter i selects a Trace 1 5 Trace i must contain data The uploaded data should be saved in its entirety by the host computer The saved data can be downloaded back to the SR785 at a later time using TPUT The TGET and TPUT comma...

Page 512: ...with the final byte of the transfer SR785 Receives n bytes and the EOI If an error is detected during transfer the Trace buffer reverts to the empty state and a command execution error occurs Serial Poll until IFC bit 7 is set in the Serial Poll status before sending another command AGET i The AGET command uploads the Arbitrary Waveform buffer to the host computer This command is valid only via th...

Page 513: ...85 A return of 0 indicates that there is no Arbitrary Waveform memory allocated Host On receipt of 1 4 byte binary long int executes a binary transfer to the SR785 of n bytes as uploaded using AGET Asserts EOI with the final byte of the transfer SR785 Receives n bytes and the EOI If an error is detected during transfer the Arbitrary buffer reverts to the empty state and a command execution error o...

Page 514: ...ET in its entirety The CGET and CPUT commands allow a host computer to save and reload the Capture buffer without using disks The download sequence is as follows Host Send CPUT i Do NOT wait for IFC to be set in the Serial Poll status SR785 Returns 1 4 byte binary long int when OK to begin binary transfer to the SR785 A return of 0 indicates that there is no Capture memory allocated Host On receip...

Page 515: ...er data to the SR785 This command is valid only via the GPIB interface The download data must be data which was originally uploaded by WGET in its entirety The WGET and WPUT commands allow a host computer to save and reload the Waterfall buffer without using disks The download sequence is as follows Host Send WPUT Do NOT wait for IFC to be set in the Serial Poll status SR785 Returns 1 4 byte binar...

Page 516: ...erfall buffer loads data into the waterfall buffer and recalls the measurement parameters which were in effect when the waterfall buffer was saved The recalled parameters include items in the Frequency Display Setup Display Options Average Window User Math and Waterfall menus ...

Page 517: ...s string is in the format Stanford_Research_Systems SR785 s n00001 ver007 In this example the serial number is 00001 and the firmware version is 007 LOCL i The LOCL command sets the local remote state The parameter i selects LOCAL 0 REMOTE 1 or LOCAL LOCKOUT 2 The states duplicate the GPIB local remote states In the LOCAL state both command execution and keyboard input are allowed In the REMOTE st...

Page 518: ...formation will be saved and the external programs must obtain this information from the user RFDR i The RFDR command sets queries the reference node direction The parameter i specifies the direction according to the following table i Node Direction 0 θ Z 1 θ Y 2 θ X 3 Z 4 Y 5 X 6 Scalar no direction 7 X 8 Y 9 Z 10 θ X 11 θ Y 12 θ Z RFNA s The RFNA command sets queries the name of the reference nod...

Page 519: ...ction 0 θ Z 1 θ Y 2 θ X 3 Z 4 Y 5 X 6 Scalar no direction 7 X 8 Y 9 Z 10 θ X 11 θ Y 12 θ Z RSNA s The RSNA command sets queries the name of the reference node The name may be up to 6 characters long RSNU i The RSNU command sets queries the number of the reference node ...

Page 520: ... request is generated The SRQ is cleared by performing a serial poll The bit in the Serial Poll status word which caused the SRQ must be cleared before this bit can cause another SRQ To clear this bit the condition which causes it to be set in the Serial Poll status word needs to be cleared For the INST DISP INPT IERR or ESB bits this is accomplished by clearing the enabled status bits in the Inst...

Page 521: ...1 The ERRE command queries the value 0 65535 of the error status enable register The ERRE i command queries the value 0 or 1 of bit i 0 15 When a bit becomes set in BOTH the Error status word AND the Error status enable register bit 3 IERR of the Serial Poll status word is set This causes an SRQ if bit 3 in the Serial Poll enable register is set To clear a bit in the Error status word use ERRS ERR...

Page 522: ...status word The value is returned as a decimal number from 0 to 65535 The DSPS i command queries the value 0 or 1 of bit i 0 15 DSPS clears the entire word while DSPS i clears just bit i INPE i j The INPE i command sets the Input status enable register to the decimal value i 0 65535 The INPE i j command sets bit i 0 15 to j 0 or 1 The INPE command queries the value of the Input status enable regis...

Page 523: ...aning 0 input is under half scale 1 input is over half scale 2 input is overloaded 3 input is HighV INPC always returns the current condition If an overload occurs and goes away INPC will not detect it Use the status words to detect momentary changes in the overload state ...

Page 524: ...s are set whenever any bit in both their respective status words AND enable registers is set Use the INSE DSPE INPE ERRE and ESE commands to set the enable register bits The INST DISP INPT IERR and ESB status bits are not cleared until ALL enabled status bits in the Instrument Display Input Error and Standard Event status words are cleared by reading the status words or using CLS Use serial poll o...

Page 525: ...s will generate a single SRQ Another SRQ from INST DISP INPT IERR or ESB can only be generated after clearing the INST DISP INPT IERR or ESB bits in the Serial Poll status word The controller should respond to the SRQ by performing a serial poll to read the Serial Poll status word to determine the requesting status bit Bit 6 SRQ will be reset by the serial poll For example to generate a service re...

Page 526: ...ey are also cleared by the CLS command Use ESE to set bits in the Standard Event enable register Instrument Status Word Bit Name Set when 0 TRIG A measurement has been triggered 1 DISK A disk operation has been completed 2 OUTP A hardcopy output operation has completed 3 TACH A tach pulse has been received 4 CAPT The capture buffer has filled 5 PAUS Measurement has been paused 6 STRT Measurement h...

Page 527: ...Display B 1 shot Waterfall has finished 14 WFB Display B Waterfall has finished drawing 15 unused The Display status bits stay set until read by DSPS They are also cleared by the CLS command Use DSPE to set bits in the Display status enable register The AVG STL LIM and SS bits are only updated when new data is available for the display no faster than 8 Hz Always test for NEWA or NEWB in the status...

Page 528: ...They are also cleared by the CLS command Use INPE to set bits in the Input status enable register To read the current input overload condition use INPC Error Status Word Bit Name Set when 0 OUTE An output error has occurred Print Plot or Dump 1 DSKE A disk error has occurred 2 FLTE A math error has occurred 3 RAME RAM memory test fails 4 ROME ROM memory test fails 5 VIDE Video memory test fails 6 ...

Page 529: ...devices in your computer The software interface uses a header file and a link library There is no initialization required for the drivers Use the TEST488 program to test the card installation Use TRTEST to communicate directly from the keyboard with the SR785 If TRTEST doesn t work then your programs will not run The example is written using the CEC library routines National Instruments GPIB Card ...

Page 530: ...to receive binary data float txBuff 2048 array of IEEE floats to send binary data int status length CEC interface routines use these variables define SR785 10 default GPIB address for SR785 subroutines at the end of this listing you may need to modify these for your interface card void TxGpib int char void GetGpib int void TxSR785 char void GetSR785 char void WaitAvg void double GetData int int vo...

Page 531: ...read data points dispAVal GetData 0 40 read DisplayA bin 40 peak dispBVal GetData 1 40 read DisplayB bin 40 printf DisplayA lf dBVpk n dispAVal printf DisplayB lf dBVpk n dispBVal Binary transfer all of DisplayA spectrum We need to send the DSPB 0 command WITHOUT waiting for IFC in serial poll status since IFC will not be set until AFTER the transfer is complete This section needs to be modified f...

Page 532: ...a listener pc a talker tarray txBuff 8192 1 status binary transfer of 8192 bytes to SR785 2048 points x 4 bytes point set EOI with last byte WaitIFC serial poll until IFC set ok to continue printf done n TxSR785 STYP 3 change source type to Arb TxSR785 I1RG 4 I2RG 4 increase the input ranges TxSR785 FSPN 2 3 2E3 narrow the span to display the spectrum GetSpace pause to look Switch to Octave Analys...

Page 533: ...status sprintf cmd DATA lf octimag imaginary part transmit cmd status last bin is the total power bin sprintf cmd DATA lf octreal 33 real part of total power bin transmit cmd status sprintf cmd DATA lf END 0 0 imag part of total power bin transmit cmd status last value terminate with EOI WaitIFC serial poll until IFC set ok to continue printf done n TxSR785 RCTR 1 5 recall Trace 5 to DisplayB to v...

Page 534: ...status indicating that the command is finished TxGpib SR785 command send command to SR785 address WaitIFC serial poll until IFC set ok to continue void WaitIFC void serial poll until IFC bit7 set command done modify for your GPIB interface stb is serial poll byte char stb do spoll SR785 stb status while stb 128 IFC if stb 32 If ESB bit set there must be a command error in the Standard Event status...

Page 535: ...o not check for both in the same query while avgdone 0x0202 0x0202 both AVGA and AVGB have occurred double GetData int disp int bin routine to move the display marker to a bin and return the data value move the marker in display disp to bin sprintf cmd MBIN d d disp bin TxSR785 cmd sprintf cmd DSPY d d disp bin read the data value at bin GetSR785 cmd return atof recv return the value as a double v...

Page 536: ...5 136 Example Program SR785 Dynamic Signal Analyzer ...

Page 537: ...SDF Files 6 4 Matlab MAT Files 6 4 Universal File Format 6 4 SR780 78D Files 6 4 Using the File Conversion Utility 6 5 Using SRTRANS 6 5 Converting Files to ASCII 6 5 Converting Files to SDF 6 7 Converting Files to 78D Format 6 8 Converting Files to MATLAB Format 6 8 Converting Files to Universal File Format 6 9 Converting Files to Capture File Format 78C 6 10 Converting Files to Arbitrary Wavefor...

Page 538: ...al programs into the SR785 for display and comparison In order to meet both these needs the SR785 is shipped with a file conversion program designed to import and export data as flexibly as possible Stanford Research Systems is committed to supporting as many file formats as possible as a result we are constantly adding new formats Contact Stanford Research Systems to obtain a list of supported pr...

Page 539: ...78C and 78W Files The SR785 uses 4 user allocable buffers to store large amounts of data These are the Channel 1 capture buffer the Channel 2 capture buffer the waterfall buffer and the arbitrary waveform buffer Capture and arbitrary waveform buffers have the same format and can be saved to disk as 78C files using the Buffer to Disk softkey or the AGET i and CGET i j commands Waterfall buffers hav...

Page 540: ...t because of specific differences between HP analyzers and the SR785 it may not be possible to exactly convert all types of measurements Matlab MAT Files MATLAB is a popular program for doing mathematics and for the analysis of numeric data Although it easy to import ASCII data directly into MATLAB it is faster and more efficient to use the binary MAT File format The conversion utilities include t...

Page 541: ...he program creates an output file with the same name as the input file and an extension appropriate to the output file type Universal Options Oxxx Output File Type asc ASCII default 78d 78D SR785 display file sdf HP SDF v3 File mat MATLAB binary file uff Universal File Format cap capture buffer 78C file arb arbitrary waveform buffer A Append to output file uff and ASCII outputs only Efilename Spec...

Page 542: ...tude m2 magnitude squared r real part i imaginary part p phase u unwrapped phase Upk dB deg Specify unit choices not all choices apply to all views pk rms pk or pp rms units peak units or peak to peak dB lin dB dBm dBSpl lin linear units deg deg rad degrees or radians Additional Options 78W input files only Wch Specify display ch A or B Sn Specify starting trace in waterfall buffer 0 is first trac...

Page 543: ...2 1 536000e 03 1 255198e 02 2 560000e 02 6 169995e 01 5 120000e 02 7 247395e 01 7 680000e 02 9 415229e 01 1 024000e 03 1 309051e 02 1 280000e 03 1 354611e 02 1 536000e 03 1 255198e 02 etc Converting Files to SDF Usage SRT785 Osdf options infile outfile Allowed Input File Types 78D Files Default Output File Extension DAT For input files which contain nodal degree of freedom informat the following S...

Page 544: ... be found by pressing System Show Version Example Convert an SR780 file named OSR780 78D to an SR785 file named NSR785 78D SRTRANS O78d OSR780 78D NSR785 78D Converting Files to MATLAB Format Usage SRT785 Omat options infile outfile Allowed Input File Types 78D Files Default Output File Extension MAT MATLAB output options Gmname Name the MATLAB matrix mname The Matrix name defaults to the filename...

Page 545: ...B array named data1 with 2 columns containing the magnitude and phase of the input data SRT785 Omat Gdata1 Cmag p MYFILE 78D M1 MAT Converting Files to Universal File Format Usage SRT785 Ouff options infile outfile Allowed Input File Types 78D Files Default Output File Extension UFF UFF output options Mrinodename Reference node name Mrnn Reference node number Mrdk Reference node direction see tabl...

Page 546: ...ints specified with the Ln option the output file is zero padded Example Convert the ASCII floating point values found in the file C1 TXT into a 10 kpoint capture file with an input range of 20 dBV 10V SRT785 Ocap L10 I20 C1 TXT Converting Files to Arbitrary Waveform Format 78C Usage SRT785 Oarb options infile outfile Allowed Input File Types ASCII Default Output File Extension 78C Arbitrary Wavef...

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