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FFT

Windowing

2-11

SR780 Network Signal Analyzer

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 or exact bin sine frequencies.

Hanning

The Hanning window is a commonly used window. However, it has an amplitude
variation of about 1.5 dB for signals which are not at exact bin frequencies and provides
only reasonable selectivity. Its side-lobes are very high and broad for off-bin frequencies.
As a result, the Hanning window can limit the performance of the analyzer when looking
at signals close together in frequency 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

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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, the
selectivity is worse. Unlike the other windows, the Flattop window has a very wide pass
band and very steep rolloff on either side. Thus, signals appear wide but do not leak
across the whole spectrum.

The Flattop window is the best window to use for accurate amplitude measurements.

The Flattop window function is

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for i = 0 .. N-1 and N = number of time record points.

BMH

The BMH window combines good selectivity and reasonable accuracy (about 0.8 dB for
signals between exact frequency bins). The BMH window has much lower side-lobes
than the Hanning window and very little broadening of non-bin frequencies.

The BMH window is a good window to use for measurements requiring a large dynamic
range.

The BMH window function is

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Summary of Contents for SR780

Page 1: ... Reference Model SR780 Network 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 2005 2014 2017 Stanford Research Systems Inc All Rights Reserved ...

Page 2: ...d against 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 ...

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 SR780 Network Signal Analyzer ...

Page 5: ...35 Swept Sine Measurement 1 43 Saving and Recalling 1 49 User Math Functions 1 55 Limit Testing 1 59 Exceedance Statistics 1 63 Chapter 2 Analyzer Basics Measurement Groups 2 3 What is an FFT 2 4 FFT Frequency Spans 2 6 FFT Time Record 2 8 FFT Windowing 2 10 FFT Measurements 2 14 Views 2 20 FFT Averaging 2 23 Real Time Bandwidth and Overlap 2 25 Waterfall Display 2 28 Capture Buffer 2 30 The Sourc...

Page 6: ...u 4 19 Display Options Menu 4 33 Marker Menu 4 37 Normal Marker Menu 4 40 Harmonic Marker Menu 4 43 Sideband Marker Menu 4 46 Band Marker Menu 4 49 Source Menus 4 51 Sine Source Menu 4 55 Chirp Source Menu 4 57 Noise Source Menu 4 59 Arbitrary Source Menu 4 62 Swept Sine Source Menu 4 67 Input Menu 4 71 Analog Input Menu 4 71 Playback Input Menu 4 81 Trigger Menu 4 85 Average Menus 4 91 FFT Averag...

Page 7: ...9 Command Syntax 5 23 Frequency Commands 5 25 Display Setup Commands 5 31 Display Options Commands 5 35 Marker Commands 5 37 Source Commands 5 44 Input Commands 5 51 Trigger Commands 5 55 Average Commands 5 56 User Math Commands 5 61 Window Commands 5 63 Waterfall Commands 5 65 Capture Commands 5 68 Memory Allocation Commands 5 69 Data Table Commands 5 70 Limit Test Commands 5 72 Marker Statistics...

Page 8: ...vi Contents SR780 Network Signal Analyzer Chapter 6 File Conversion Why File Conversion 6 2 Supported External File Types 6 3 SR780 File Types 6 4 Using the File Conversion Utility 6 5 ...

Page 9: ...ing 2 62 Figure 2 5 Resistive Coupling 2 63 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 Single 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 14 Figure 3 8 Marker Position Bar 3 15 Figure 3 9 Status Indicator Panel 3 17 Figure 3 10 Front Panel Keypad 3 22 ...

Page 10: ...viii SR780 Network Signal Analyzer ...

Page 11: ... 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 T 2 T 2 T 4 T 4 0 T 2 Averaging RMS Vector Peak Hold Linear or Exponential Preview Time Records Equal Confidence Analysis Harmonic Sideband Band THD THD N Limit Testing Data Table Exceedance LN Statistics Waterfall Slice User Math Conjugate M...

Page 12: ...t 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 Interfaces RS232 serial Centronics parallel and IEEE 488 Help On screen help system provides Operating Manual and Programming Reference on line ...

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: ...0 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 Ampli...

Page 15: ...ance 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 80 dBc fundamental 30 kHz 74 dBc fundamental 30 kHz Two Tone Amplitude Accuracy 1 of setting 0 Hz to 102 4 kHz 0 1 Vpk to 5 Vpk high impedance load Offset 0 V...

Page 16: ... 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 plotters Print Plot to RS232 or IEEE 488 interfaces or to disk file Additional file formats inc...

Page 17: ...nction for these measurements In This Chapter General Installation 1 3 Caution 1 3 Line Voltage Selection 1 3 Line Fuse 1 3 Line Cord 1 3 Power Switch 1 3 Screen Brightness 1 3 Fan 1 3 Front Panel Quick Start 1 4 Hardkeys 1 4 Softkeys 1 4 Knob 1 4 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 and Ran...

Page 18: ...1 2 Getting Started SR780 Network Signal Analyzer ...

Page 19: ... 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 SR780 has a detachable three wire power cord for connection to the power source and to a protective gro...

Page 20: ... menu The FUNCTION keys perform common functions such as Auto Scale and Auto Range These keys can be accessed at any time Softkeys The SR780 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...

Page 21: ...onse 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 Averaging Very long averaging times for any measurement may give the appearance that the display does not update Check the FFT Number Of...

Page 22: ... 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 the backspace key This will reset the analyzer into the default configuration The an...

Page 23: ...ce 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 be greater than normal 3 Press Source Select the Source menu Press Sine Choose Sine o...

Page 24: ... the knob to move the Marker around Take a look at some of the harmonics The knob normally adjusts the Marker Position within the active display DisplayA in this case If a menu box is highlighted with a softkey the knob adjusts the selected parameter shown in the entry field at the top of the screen 9 Let s look at the fundamental only You can also use the Span Up and Span Down keys to adjust the ...

Page 25: ...t or Reference to the amplitude of the fundamental The Marker Position above the graph now reads relative to this offset 0 dB This is indicated by the in front of the Marker Position reading A small flag shaped symbol is located at the screen location of the reference Use the knob to move the Marker to the harmonics The Marker Position shows the distortion peaks relative to the fundamental Press M...

Page 26: ...icate 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 measurement example You should have a feeling for the basic operation of the menus knob and numeric entry marker movement and some ...

Page 27: ...s 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 Window Select the Window menu Press Window Adjust the FFT Window function Select Uniform with the knob and press Enter The Chirp source requires the us...

Page 28: ... 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 Marker Regi...

Page 29: ... show the phase of the transfer function Press Auto Scale B Scale DisplayB to show the entire phase transfer function 10 Press Display Options Select the Display Options menu Press X Axis The graph looks better on a log x axis Select Log with the knob and press Enter Now both displays have a log x axis 11 Let s link the Markers together Press Active Display Make DisplayA top the active display Pre...

Page 30: ...ve 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 measur...

Page 31: ...y 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 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 Range to agree with the signa...

Page 32: ... kHz The SR780 allows the two displays to have differing Spans and Start frequencies Many parameters affect the displays separately Linking is a convenient way to adjust the two displays together and keep their settings the same The default settings link many measurement parameters such as frequency and averaging together as found in many other instruments 7 Press Average Select the Average menu P...

Page 33: ...mum of key presses 9 Press Display Setup Select the Display Setup menu Press Units Let s change the Units for both displays Press Link Link the Units parameter default is unlinked Select dBVrms with the knob and press Enter Both displays Units become dBVrms with a single parameter entry The Units remain linked until unlinked with the Link key 10 Press Y Max Let s change the Top Reference of the gr...

Page 34: ...enu and change Marker to Link Press Marker Min Marker Min moves the Marker in the active display B to the graph minimum Press Link then Marker Min Pressing Link first moves both Markers to their graph minimums at the same time Link preceding a function key generally performs the function on both displays at once Link Auto Scale matches the active display Span Up and Span Down are always linked Thi...

Page 35: ...DC level of the output is near 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 s...

Page 36: ...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 is linked by default Select Uniform with the kno...

Page 37: ... is 1024 points long so we need about 500 bins points of negative delay to 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 of the time record The amplitude of the windowed time record is not the same as the amplitude...

Page 38: ... press Enter Free Run requires no trigger The measurements are not triggered If the generator is set to 256 Hz pulse rate the signal will drift slowly in the time record This is because the SR780 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 ...

Page 39: ...Triggering and the Time Record 1 23 SR780 Network Signal Analyzer ...

Page 40: ...1 24 Triggering and the Time Record SR780 Network Signal Analyzer ...

Page 41: ...rce 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 Link Auto Scale A Auto Scale DisplayA and change the scale of DisplayB to match DisplayA The Octave measurement dis...

Page 42: ...hed 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 Integration Time is the averaging time constant All Octave measurements ar...

Page 43: ...owered 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 In this case both displays will always hav...

Page 44: ... More Show More Input 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 according to how people hear and perceive ...

Page 45: ...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 4 Press Capture Select the Capture menu Press Allocate Memory The data memory is allocated between Capture Waterfall and Arbitrary Waveform storage Memory is allocated in blocks Each block can store 2 kPoints The total num...

Page 46: ...re The buffer will take 7 73 seconds to fill Since the Capture Mode is 1 Shot the capture stops once the buffer is full During this time Capture indicator is highlighted and the Capture Progress indicator shows how much of the buffer has been filled up to 100 After capture is complete the Capture indicator shows Cap Data indicating that the Capture buffer contains data Press Active Display Make Di...

Page 47: ...ack only a portion of the buffer if desired Press 1 9 8 0 and Enter Choose the entire buffer by setting the Playback Length equal to the Capture Length Press Playback Mode Playback can be 1 Shot once through the buffer and stop or Circular repeat when finished Use the knob to select 1 Shot and press Enter Choose 1 Shot Playback stops when the end of the buffer is reached The Playback Progress indi...

Page 48: ...d signal Use the knob to decrease the rate to 131 1 kHz and press Enter Choose 131 1 kHz as the Sampling Rate The capture bandwidth is now 51 2 kHz reduced from 102 4 kHz During playback from this buffer the measurement bandwidth will not be allowed to exceed 51 2 kHz Press Start Capture Capture both inputs for 7 73 seconds Watch for the Capture Progress indicator to reach 100 10 Disconnect the si...

Page 49: ... of the equivalent real time analog input measurement 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 memory we can choose to display every stored time record Press Start Reset Start the playback at the beginning of the buffer In this case all 1000 time records are measured AND displayed The d...

Page 50: ...to playback an exact number of time records This way the last record doesn t wrap around and use points from the start of the buffer At this span with no overlap each time record is 62 5 ms long The capture sampling rate was 131 1 kHz so 2 kPoints of capture represents 15 625 ms of data Thus each time record is 8 kPoints of capture long We want the Playback Length to be an integer multiple of 8 kP...

Page 51: ...e 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 Change the lowest band in the display Use the knob to select 50 Hz and press Enter Select 50 Hz ...

Page 52: ...Octave group Press Averaging Type Change the Averaging Type Use the knob to select Linear Time and press Enter Use Linear Time for best time resolution Exponential Time averaging takes about 5 integration times to fully respond to a transient Linear Time averaging responds in a single integration time Press Integration Time Change the Integration Time Use the knob to select 8 ms and press Enter Ch...

Page 53: ...urce 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 Enter Choose One Shot to trigger the noise burst only once at the start of the measurement 8 Press Start Reset Start Reset starts the measurement Since the measurement is triggered no...

Page 54: ...isplay Use the knob to select Waterfall and press Enter Choose Waterfall display This shows measurements scrolling down Without waterfall storage this is purely graphical no data can be read from measurements other than the most recent Press Storage Select waterfall Storage Use the knob to select One Shot and press Enter Choose One Shot to fill the waterfall buffer once and stop Press Total Count ...

Page 55: ...n 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 marker Z position is displayed next...

Page 56: ... 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 this way Use the knob to move the marker around in the waterfall slice DisplayB Note that the first 12 records 96 ms show a large value for Leq during the noise burst If this was a real ...

Page 57: ...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 the Waterfall menu which you should familiarize yourself with The transient response of a...

Page 58: ...1 42 Waterfall Display SR780 Network Signal Analyzer ...

Page 59: ...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 Select the Input menu Press Ch1 Input Range Adjust the Ch1 input range Press 2 and Enter Set the range to 2 dBV 3 Press Display Setup Select the Display Setup menu Press Measurements Group There are three Measurement Groups FFT Octave and Swept Sine...

Page 60: ...ay 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 Transfer Function with the knob and press Enter Choose Transfer Function filter output divided by filter input Press Units Transfer function is unitless Change the display units Select dB with the knob and press En...

Page 61: ...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 62: ...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 allowable input range 10 Press Freq Select the Frequency menu Press Auto Resolution Change the Auto Resolution mode Select On with the knob and press Enter Choose Auto Resolution on If successive points differ by less t...

Page 63: ...e sets the largest source output allowed This is useful whenever the transfer function has substantial gain as well as attenuation or if a test requires a constant level within the device under test usually input or output In this case Auto Level is not really required but illustrates its use Press Active Display Change the active display to DisplayB which is still measuring the spectrum of Ch2 Pr...

Page 64: ...er This concludes this measurement example You should have a basic understanding of Swept Sine measurements The Input Range Resolution and Source Level optimizations greatly extend the dynamic range of the measurement while minimizing the measurement times ...

Page 65: ...show the entire 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 Select the Inpu...

Page 66: ...e 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 Enter...

Page 67: ...tive 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 that the Measurement Group and Measurement menu boxes are not gray This is because these parameters may ...

Page 68: ...mally 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 Display to Disk Save the measurement data in DisplayA to disk using the specified file name The extension 78D is appended automatically Press File Name Enter another file...

Page 69: ... 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 this example Remember Off Line displays are showing stored data not live ...

Page 70: ...1 54 Saving and Recalling SR780 Network Signal Analyzer ...

Page 71: ...ce 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 Window Select the Window menu Press Window Adjust the FFT Window function Select Uniform with the knob and press Enter The Chirp source requires the use of the Uniform window...

Page 72: ...ands 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 identical to the normal measurement We are going to define a transfer function FFT2 FFT1 As soon as the operand is entered the display sw...

Page 73: ...ter 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 the knob to select Real Part and press Enter Choose Real Part The units a...

Page 74: ...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 SR780 measurements User Functions can als...

Page 75: ...ntal 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 The default source is a 10 24 kHz sine Press Auto Scale A Scale the display to show all of the data 3 Press Analysis Select the Analysis menu Press Limit Test Choose Limit Test Press Edit Limits Show the Edit Limits menu We can t turn on any testing until limit...

Page 76: ...yed to the left of the graph In this case Fail should be shown The limit that we drew is an upper limit Since the data peak exceed this limit the test fails Press Edit Limits Go back to the Edit Limits menu Press Shift All Select Shift All limit segments This moves all of the segments together In this case there is only one segment Press 7 Enter Enter 7 to move the segment up by 7 dBVpk The new se...

Page 77: ...ordinates are displayed in the menu Press Limit Type Select the Limit Type for segment 0 Use the knob to select Lower and press Enter Change the limit to a lower limit The limit test now fails since data falls below the segment Press Return Return to the Limit Testing menu Press Limit Beep Select Limit Beep Use the knob to select On and press Enter On enables the audible alarm This alarm alerts yo...

Page 78: ...e 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 Limit Testing menu Press Limit Segments Select Limit Segments Use the knob to select Show and press Enter Show the segments The two segments defined earlier are still available This concludes this example Limit testing is a powerful tool for repetitive tests In an auto...

Page 79: ...he 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 Source Select the Source menu Press Noise Choose Noise as the source type Octave measurements are generally u...

Page 80: ...00 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 Start Reset Start the measurement This resets the waterfall buffer New measurements are added to the waterfall buffer every 100 ms The number of records stored in the waterfall is shown in the Vertical Scale Bar and increments to 100 ...

Page 81: ...erence graph is shown in half intensity In this case the reference graph is the level of each octave bin which is exceeded only 1 of the time L1 Note that the exceedance is also calculated for the power bin Leq Press Pause Cont Continue the live measurement Note that the live measurement data rarely exceeds the reference graph 9 Press Pause Cont Pause the live measurement again Press Exceedance Pc...

Page 82: ...a common measurement for environmental noise levels such as airports or highways Change the octave integration time and waterfall storage interval to optimize the measurement rate Use a larger waterfall buffer up to 2000 measurements per display for long monitoring times ...

Page 83: ...d 2 15 Orbit 2 15 Cross Spectrum 2 15 Transfer Function 2 15 F2 F1 2 15 F2 F1 2 16 Force Exponential 2 16 Coherence 2 16 Auto Correlation 2 16 Cross Correlation 2 17 Capture Buffer 2 18 User Function 2 19 Views 2 20 Log Magnitude 2 20 Linear Magnitude 2 20 Magnitude2 2 20 Real Part 2 20 Imaginary Part 2 20 Phase 2 20 Unwrapped Phase 2 21 Nyquist Plot 2 21 Nichols Plot 2 22 FFT Averaging 2 23 RMS A...

Page 84: ...tion 2 44 Averaging Settling and Integration 2 44 Sweep Frequency and Auto Resolution 2 45 Input Auto Ranging 2 46 Source Auto Level and Ramping 2 46 Trace Storage 2 48 User Math Functions 2 49 What is a User Function 2 49 Measurement Groups and Traces 2 49 Units 2 49 Operands 2 50 X Axis 2 50 Operations 2 51 User Function Limits 2 52 Example Functions 2 53 FFT Group 2 53 Octave Group 2 54 Swept S...

Page 85: ...data is integrated over exact source cycles The data processing in each group is governed by the parameters 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 three different sets of parameters one for each group For other menus part or all of the menu is unavailable in certain groups ...

Page 86: ...rs 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 frequency component of the signal then the sampled data will accurately represent the input signal in the ...

Page 87: ...n 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 measured yet This is not a practical solution Instead the way to measure the signal accurately is to lengthe...

Page 88: ... 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 with narrower frequency...

Page 89: ...s 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 heterodyne frequency If ...

Page 90: ...ge 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 original 102 4 kHz span is represented by a ...

Page 91: ...ncies 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 real or imaginary part The sampling rate ...

Page 92: ...ls 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 signal t...

Page 93: ... 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 the selectivity is worse Unlike the other windows the Flattop window has a very wide pass band and very steep rolloff on either side Thus signals appear wide but do not leak across the who...

Page 94: ... to be continuous with the end of the time record to prevent broadband leakage in the spectrum Exponential The Exponential window attenuates the time record with a decaying exponential time constant This window is often used in impact testing on the response channel to remove oscillations which last longer than the time record The signal should be zero at the start of the time record in order to b...

Page 95: ...er interface Trace to Window automatically changes the window of the active display to the User window Trace to Window is the only way to choose the User window The User window is lost if the window type is changed To switch back and forth between a User window and another window keep using Trace to Window Remember window functions have a great deal of impact on the resulting FFT spectrum A poorly...

Page 96: ...e the span have been filtered out Baseband time records are entirely real they have no imaginary part For zoomed spans spans which start above DC the time record display does NOT resemble the original data The data has been frequency shifted Signals at the center of the span appear at DC while frequencies at both edges of the span appear as high frequencies Zoomed time records are complex they hav...

Page 97: ...the window selected in the Window menu The cross spectrum contains both magnitude 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 produ...

Page 98: ... a two channel measurement defined as Coherence Mag2 VecAvg CrossSpec Pwr1 Pwr2 where CrossSpec conj FFT1 FFT2 Pwr1 Mag2 RMSAvg FFT1 Pwr2 Mag2 RMSAvg FFT2 Averaging is always On and the Averaging Modes are defined by the measurement above The Type and Number Of Averages are still selected in the Average menu Both channels use the window selected in the Window menu Coherence is a unitless real quan...

Page 99: ... in wrap around where the correlation starts to repeat itself To avoid this special windows which zero half of the time record are used The 0 T 2 window zeroes the second half of the time record and the T 4 T 4 window zeroes the first and last quarter of the time record The T 2 T 2 is a uniform window which should only be used on data which is self windowing lasts less than half of the time record...

Page 100: ... data by choosing Playback as the Input Source in the Input menu The capture buffer is often very long To graphically expand a region of the display use the Pan and Zoom functions in the Display Setup menu The capture buffer display can automatically pan with the capture fill or playback progress through the buffer During capture fill if the capture buffer accumulates points faster than they be di...

Page 101: ...on User Functions defined within the FFT Measurement Group may include FFT measurements Use the User Math menu to define a math function A User Function may not be selected as the measurement if it uses a Trace which is empty or which contains data taken in a different Measurement Group See User Math later in this section for more ...

Page 102: ...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 is zero for all points Imaginary data arises from the multiplication of the input time data by sine and cosine heterodyne Signals in phase with cosine result in real data signals in phase with sine result in imaginary data The real and im...

Page 103: ...in frequencies whenever possible Unwrapped Phase Unwrapped Phase view graphs the phase of the measurement data as a continuous function without wrapping around at 180 degrees This view is generally meaningful only for measurements which have data at every frequency point such as chirp source or swept sine The phase θ is calculated for each point as in the wrapped Phase view The wrapping starts at ...

Page 104: ...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 measurements which have data at every frequency point such as chirp source or swept sine The marker readout shows the log magnit...

Page 105: ...rms averaged measurement is limited to the first quadrant 0 90 deg Vector Averaging Vector averaging computes the average of the real part X and imaginary part Y of a measurement according to Xavg mean X and Yavg mean Y Linear averaging computes the equally weighted mean of X and Y over N measurements Exponential averaging weights new data more than old data and yields a continuous moving average ...

Page 106: ... displayed below the graph 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 stopping Each completed average counts as a single waterfall record Exponential Weighting Exponent...

Page 107: ...is 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 SR780 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 I...

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: ...l the measurement is settled When the time record increment is 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 If the measurement is vector averaged then Time Record Increment is ignored 100 is used Overlapping time records are not allowed in this case Triggering If the measureme...

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: ...ored records to be determined exactly In Octave group the Storage Interval is set as a time In this case a snapshot is stored to memory every Storage Interval amount of time The Skip Storage Interval has no effect if the measurement is linear averaged In this case the result of each complete linear average is stored in the waterfall buffer and the average is reset and started over again Change the...

Page 112: ... at less than the maximum sampling rate restricts the playback measurement span to sampling rate 2 56 The Capture Length is selected in 2 kPoint 2048 increments limited by the user memory allocation A single input or both inputs may be captured The maximum capture length for a single input is twice the length for both inputs at a given memory allocation Capture Fill To start capture press the Star...

Page 113: ...frequency or highest Octave band during playback The Average Window and Waterfall menus all operate normally during playback The Playback Mode can be either 1 Shot once through the buffer or Circular repeat over and over 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 bu...

Page 114: ...necessarily for a real time record to elapse between updates In this case Every Time Record playback displays the measurements of all captured time records much faster than Normal Speed real time playback When the playback is in Octave Group playback is always Normal Speed Capture as the Arbitrary Source The contents of the capture buffer can be used as the arbitrary source This allows a captured ...

Page 115: ... measuring transfer functions 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 mechanical systems or even the audio response of an entire room White noise provides ...

Page 116: ...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 the source frequencies must be set to a multiple of the linewidth in orde...

Page 117: ...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 start and stop bands for the ...

Page 118: ...emory 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 region of the display use the Pan and Zoom functions in the Display Setup menu The capture buffer display can ...

Page 119: ...ear 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 Horizontal Scale Bar below the graph When the Integration Time has been completed the measurement stops and Done is displayed below the graph If Waterfall Storage i...

Page 120: ...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 and continues to change even after a linear average is complete Standard measurements use either 125 ms Fast or 1000 ms Slow Note that the lowest octave band places a limit on the averaging time The stan...

Page 121: ...r 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 and continues to change even after a linear average is complete The last bin in the measurement displays the Peak sound level The last bin is labeled P In a User Math function ...

Page 122: ...is changed a settling 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 set...

Page 123: ...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 124: ...nge at each frequency for the best signal to noise When the frequency is in the stop band the return signal to Channel 2 is 80 dBV or less The input range of Channel 2 is adjusted to 50 dBV for these frequencies eliminating the noise floor limitation The depth of the zero in the response as well as the shape of the stop band are clearly resolved Swept Sine Measurement Setup The advantages of the s...

Page 125: ...ow the current sweep point The current frequency is displayed at the top of the screen Swept Sine Measurements Only Spectrum Cross Spectrum Transfer Function and User Function measurements are available Time record capture and waterfall are not available in this measurement group Spectrum The swept sine spectrum is simply the measurement of a single channel over a sweep The spectrum is complex it ...

Page 126: ...armonics A long Integration Time results in a narrow detection bandwidth at the source frequency This improves signal to noise at the cost of longer measurement times This is similar to the linewidth of an FFT However in the FFT the linewidth is exactly related to the frequency span Span FFT Resolution In swept sine the Integration Time is independent of the frequency span Thus wide spans can be m...

Page 127: ...s then the sweep will take larger steps skipping frequency points Each successive time this threshold is met the step size is increased until the Maximum Step Size is reached This speeds up the sweep in regions where the response is flat varies less than the Faster Threshold If a measurement differs from the previous measurement by more than the Slower Threshold for EITHER channel then the sweep r...

Page 128: ...lly at very low frequencies it might be better to set the range manually to avoid increasing an already long sweep time Auto Ranging is set for each channel separately and can be turned on and off during the sweep The manual input range can be changed at any time during the sweep as well Source Auto Level and Ramping The source amplitude parameters for a swept sine measurement are set within the S...

Page 129: ...range The Reference Upper and Lower limits are the allowable tolerances for the Reference Channel The source level is changed only if the reference channel measures an input which exceeds the Ideal Reference by more than the Upper Limit or which is less than the Ideal Reference by more than the Lower Limit In cases where the reference channel input must be limited the Ideal Reference plus the Uppe...

Page 130: ...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 131: ...roup allows different Operands FFT 1 Oct 1 or Swept Sine Spec 1 as well as different 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...

Page 132: ...els each with a different window Force exponential transfer function for example FFTu 1 and FFTu 2 are un windowed FFT s of the Ch1 and Ch2 inputs Octave and Swept Sine measurements are always averaged measurements Use the Average menu to set the averaging parameters Auto_Corr 1 Auto_Corr 2 X_Corr F2 F1 and Coherence are all averaged FFT measurements regardless of whether averaging is On or Off in...

Page 133: ...nction s X axis type or length as well Operations Operands are combined with Operations to define a function Arithmetic operations x combine operand terms on a point by point basis It is the user s responsibility to ensure that the operand terms have the correct X axis type and lengths required to produce meaningful results View operations Mag Mag2 Phase Real Imag simply convert the complex operan...

Page 134: ...eraging on the operand Averaging is performed regardless of the Average Off On selected in the Average menu The menu still determines the Average Type and Number of Averages d dx is the derivative operator The derivative is performed with respect to the X axis bin number not the x axis values For example to convert d dx to d df for a linear frequency display divide by the frequency spacing of the ...

Page 135: ...unctions FFT Group The pre defined FFT measurements use the window specified for the display in the Window menu regardless of input channel With User Math it is possible to define 2 channel measurements which use a different window for each input channel by using FFTa 1 and FFTb 2 instead of FFT 1 and FFT 2 FFTN Avg FFT N TimeN Time N WinTimeN Time N x Trace Window 800 line baseband FFT only use W...

Page 136: ...Tu 2 x Conj FFT 1 Peak Hold or RMS averaging IFFT VecAvg FFTu 2 x Conj FFT 1 Vector averaging IFFT VecAvg FFTu 2 x Conj VecAvg FFT 1 In all cases the VecAvg is always performed Octave Group OctN Oct N Swept Sine Group SpecN Spec N Cross Spec Conj Spec 1 x Spec 2 Trans Func Spec 2 Spec 1 ...

Page 137: ...2 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 that the signal does not fall dramatically after pushing the Input Range to a very high i...

Page 138: ...ise the overall noise is 102 102 1 2 or 14 nVrms Hz Input Impedance The input impedance of the SR780 is 1 MΩ If a higher input impedance is desired then the SR550 remote preamplifier must be used The SR550 has an input impedance of 100 MΩ and is AC coupled above 1 Hz Anti aliasing Filter After all of the signal amplification there is an anti aliasing filter This filter is required by the signal di...

Page 139: ...able 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 displayed in units of the actual physical quantity being measured such as m s2 or Pascals T...

Page 140: ...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 not rejected at all Differential Connection A B The second met...

Page 141: ...ing 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 noise in the measurement of the AC signal If the signal frequency e...

Page 142: ...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 143: ...lyzer 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 may still be larger than a weak signal This is ...

Page 144: ...nductive 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 winding Figure Chapter 2 4 Inductive Coupling Cu...

Page 145: ...ents 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 example can result in electrical n...

Page 146: ...pically 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 junction in reverse polarit...

Page 147: ... Status Indicators 3 17 Input Ranges 3 17 OverLoads 3 17 Input Configurations 3 17 AWt 3 17 ArmWait Trig wait Trig Acquire 3 17 Run Pause Done 3 18 Analog Playback 3 18 Real Time 3 18 Sweep Frequency 3 19 Capture Progress 3 19 No Cap Cap Data 3 19 Link 3 19 Enter 3 19 ALT 3 20 GPIB RS232 3 20 Comm Error 3 20 SRQ 3 20 Local Remote LOCK 3 20 macro 3 22 Keypad 3 23 Normal And Alternate Keys 3 23 Menu...

Page 148: ...o Scale A 3 32 Auto Scale B 3 32 Auto Range Ch1 3 32 Auto Range Ch2 3 33 Span Up 3 33 Span Down 3 33 Marker Ref 3 34 Display Ref 3 34 Marker Center 3 34 Marker Max 3 35 Marker Min 3 35 Show Setup 3 35 Macros 3 36 Keypad Macros 3 36 Choosing From Lists 3 36 Menus 3 36 ...

Page 149: ...elow the softkeys The firmware revision serial number memory size and calibration dates of the unit are displayed when the power is turned on This power on screen may be displayed at any time using System Show Version Caution This instrument may be damaged if operated with the LINE VOLTAGE SELECTOR set for the wrong AC line voltage or if the wrong fuse is installed Hardware Reset Turn the power on...

Page 150: ...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 151: ... 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 152: ... the chassis by 1 MΩ 0 01 µ F 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 Transfer Function Channel 2 is the respo...

Page 153: ...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 154: ...CTOR set for the wrong AC line voltage or if the wrong fuse is installed Do not attempt to service or adjust this instrument while it is plugged into a live outlet Line Voltage Selection The SR780 operates from a 100V 120V 220V or 240V nominal AC power source having a line frequency of 50 or 60 Hz Before connecting the power cord to a power source verify that the LINE VOLTAGE SELECTOR card located...

Page 155: ...ote menu To connect the SR780 to a PC serial adapter which is usually a DTE use a straight through serial cable A serial plotter or printer may be connected to the RS232 port Select the Serial interface as the Output Destination and choose the Printer or Plotter Type in the Output menu Parallel Printer Connector Attach a parallel printer to the Printer port Use a standard printer cable Select the ...

Page 156: ...ve 1 Hz Do not use either preamp to measure signals below 1 Hz The SR780 does not compensate for the gain of the preamp Both preamps operate at their highest gain Measurements made by the SR780 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 ...

Page 157: ...asurements 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 DisplayA is always on top Marker Position Bar When highlighted indicat...

Page 158: ...pansion 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 full intensity FFT and Octave measurements are unsettled when the frequency span or resolution is changed and when the input signal path is changed gain filters etc ...

Page 159: ...le per division is shown between Y Max and Y Min The units and scale division are selected in the Display Setup menu The Input Transducer Unit Conversion shows the Engineering Unit Conversions for the measurement input either Ch1 or Ch2 If the display is showing a 2 channel measurement such as transfer function the conversion for both inputs are shown Ch1 above Ch2 The No Anti Aliasing Filter warn...

Page 160: ...d 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 Source Auto Level no Auto Range no Auto Resolution This Sweep Time is simply the ...

Page 161: ...ys moves the marker unless a menu softkey has been pressed and an entry field is displayed at the top of the screen Marker Position Bar Figure Chapter 3 8 Marker Position Bar The Marker Position Bar is displayed above each graph The first value is the marker frequency time or bin number If the display is a waterfall the waterfall record number is also shown The second value is the marker Y Positio...

Page 162: ...Display in the new display scale press Alt Snap Ref Menu Display The softkey menu boxes define the functions of the softkeys to the right of the screen Related functions and parameters are grouped into menus Pressing each of the Menu keys displays a different set of menu boxes There are three types of softkeys buttons lists and numeric values A button performs a function such as Full Span A list p...

Page 163: ...load 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 at the input the overload indicator displays HighV on a bright background The analyz...

Page 164: ... 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 displayed increment is 200 the start of the next time record is advanced from the start of the previo...

Page 165: ...ins data for playback Link When an unlinked display parameter is being entered or modified the Link indicator next to the top of the menu reads either DispA or DispB whichever is the active display Parameter entry or selection modifies only the active display To change which display will be modified press Active Display When a linked parameter is highlighted the Link indicator reads Link Parameter...

Page 166: ...s displayed when the computer interface is idle RS232 flashes when there is activity on the RS232 interface GPIB flashes when there is activity on the GPIB interface ERR flashes whenever a computer interface error occurs such as illegal command or out of range parameter is received SRQ This indicator is on whenever a GPIB Service Request is generated by the SR780 SRQ stays on until a serial poll i...

Page 167: ...Status Indicators 3 21 SR780 Network Signal Analyzer ...

Page 168: ... Signal Analyzer macro Record indicates that a keypad macro is being recorded Use Macro Rec to start recording Play indicates that a macro is being played Use Play Macro to playback a stored macro See Macros later in this chapter for more ...

Page 169: ...ve 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 necessary ...

Page 170: ...ay format grid user units and log X axis Marker Configure the markers Source Turns on and configure source Input Configures the signal 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 FFT measurement window Waterfall Setup waterfall displays and storage Capture Setup the time ...

Page 171: ...f 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 selections will be listed at the top of the screen Use the knob to make the desired selection If a vertical thermometer appears at the right of the entry field then the selection list...

Page 172: ...ss 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 the keys are pressed The _ is the entry point If an error is made the backspace key will erase the last character Pressing the same softkey again or another softkey to modify another parameter will abort the entry op...

Page 173: ... Pause Cont simply resumes data acquisition without resetting the average For Linear FFT averaging Pause Cont will complete the current average If the linear average was already complete Pause Cont has no effect For Swept Sine measurements Pause Cont simply resumes the sweep where it was paused For Octave Analysis measurements Pause Cont resets the averages before starting again same as Start Rese...

Page 174: ...Active Display switches which display is active as indicated by the highlighted Marker Position bar above the graph The active display determines which display s parameters are displayed in the menus For example activating DisplayA and pressing Display Setup allows you to select the measurement for DisplayA Pressing Active Display once makes DisplayB active and allows you to select the measurement...

Page 175: ...he function is performed on the active display If Link is pressed immediately before then the function is performed on both displays at once Link only affects the next key pressed If the next key is not a function key then it has no affect Linking affects each function differently See the function key definitions for more information When no parameter softkey is highlighted turning the knob adjust...

Page 176: ...he units of a numeric parameter while recording a macro The units choices are numbered starting with 0 as the first leftmost units To play a recorded macro press Play Macro Alt Start Reset and choose the desired macro with the knob To edit a recorded macro use System Edit Macro End Rec Alt Stop Capture End Rec stops recording a macro To play a recorded macro press Play Macro Alt Start Reset and ch...

Page 177: ...n 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 SVTR d i Trace to Display Alt Help Local Trace to Display recalls Trace data to the active display Select a Trace 1 5 with the knob and press Enter to recall the Trace data to the active display The active display will be set to Off Line when data is recalle...

Page 178: ...r time bins which are not shown do not figure in the auto scaling calculations Link Auto Scale B auto scales DisplayB and sets the vertical scale of DisplayA to match DisplayB 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 menu In Auto Range the Input Range is adjusted automatically acco...

Page 179: ...n of both 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 Octave group Span Up moves the octave measurement span of both displays up by an octave Span Up affects each display independentl...

Page 180: ...ata The Reference Display is graphed in half intensity This allows comparison of new data with the stored Reference Display 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 Frequency Span or the Measurement turns the Reference Display off Changing the ...

Page 181: ...ximum 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 data which is in the display If the minimum value occurs at more than one location then the one closest to the left edge is found If the Marker Mode in the Marker menu is Normal Marker Min centers the Marker Region around ...

Page 182: ... 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 the pa...

Page 183: ...alues 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 key or function P...

Page 184: ... 4 48 Band Ratio Mode 4 49 Band Power 4 49 Band Ratio 4 49 Source Menu 4 51 Source Off 4 51 Source On 4 51 Sine 4 51 Chirp 4 52 Noise 4 52 Arbitrary 4 53 Sine Source Menu 4 55 Frequency 1 4 55 Amplitude 1 4 55 Offset 4 56 Tone 2 4 56 Frequency 2 4 56 Amplitude 2 4 56 Chirp Source Menu 4 57 Amplitude 4 57 Burst 4 57 Source Display 4 58 Noise Source Menu 4 59 Amplitude 4 59 Type 4 59 Burst 4 60 Sour...

Page 185: ...ime 4 97 Accept 4 97 Reject 4 98 Octave Average Menu 4 99 Averaging Type 4 99 Integration Time 4 100 Confidence 4 101 Power Bin 4 101 Linear Average Mode 4 101 Swept Sine Average Menu 4 103 Settle Time 4 103 Settle Cycles 4 103 Integration Time 4 104 Integration Cycles 4 104 User Math Menu 4 107 Function 4 107 dB Conversion 4 107 Edit Function 4 107 Operands 4 108 Operations 4 110 Function String ...

Page 186: ... Statistics Menu 142 Start Index 142 Stop Index 142 Exceedance Pct 143 Calculate Excd 143 Disk Menu 4 145 File Name 4 145 Current Directory 4 146 Display to Disk 4 146 Disk to Display 4 146 Settings to Disk 4 146 Recall Settings 4 147 Trace to Disk 4 147 Disk to Trace 4 147 Buffers 4 147 Disk Upkeep 4 148 Nodal Degree of Freedom Menu 4 149 Reference Name 4 149 Reference Number 4 149 Reference Dire...

Page 187: ...veride REM 4 174 Baud Rate 4 174 Word Length 4 175 Parity 4 175 View Qs 4 175 System Preferences Menu 4 176 Key Click 4 176 Alarms 4 176 Alarms Volume 4 176 Done Volume 4 176 Audible Overload 4 177 Screen Saver 4 177 Screen Saver Delay 4 177 Frequency Format 4 177 Node Info Prompt 4 178 System Date Time Menu 4 179 Time 4 179 Date 4 179 System Diagnostics Menu 4 180 Keypad Test 4 180 Keyboard Test ...

Page 188: ...4 6 Menus SR780 Network Signal Analyzer ...

Page 189: ... 2 19 times the Base Frequency 195 3 mHz or 191 mHz in factors 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 Acquisitio...

Page 190: ...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 ways to change the Span If the new frequency Span would extend below 0 Hz or above the FFT Base Frequency then t...

Page 191: ...base frequency by dividing by powers of 2 102 4 kHz is commonly used and has an advantage at narrow spans where even bin frequencies of 1 Hz 0 5 Hz etc are available 100 0 kHz has even bin frequencies of 1000 Hz 500 Hz etc at wide spans Changing the FFT Base Frequency affects ALL of the FFT frequency parameters as well as the source frequency All FFT measurements on BOTH displays use the same Base...

Page 192: ...This entry field can be linked to both displays using the Link key If either display is a two channel measurement Transfer Function Cross Spectrum Or Cross Correlation then the Center frequencies are automatically linked If either measurement is Cross Correlation then the Center frequency of both displays is set to Span 2 Command FCTR d f End Frequency Set the End frequency of the active display F...

Page 193: ...FFT Frequency Menu 4 11 SR780 Network Signal Analyzer Command FEND d f ...

Page 194: ...ave 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 octaves Increasing the Highest Band will also increa...

Page 195: ...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 center frequencies are calculated according to the ANSI standard The displayed frequencies are sometimes rounded to even values for a simpler display The filter shapes are third order Butterworth with...

Page 196: ...king 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 measured Choosing 1 Octave Channel may change the current Measurements so that both displays use the same input Command OCHN d i ...

Page 197: ...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 198: ...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 199: ...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 200: ...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 201: ... spectrum of finite time records 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 discrete frequency points along the way The Measurement Group may not be changed if the Input Source is Playback from captur...

Page 202: ...e accurate measure of the rms signal amplitudes as well as the rms noise levels Time Record A time record is simply a sequence of data samples The length of the time record is the FFT resolution span For baseband spans spans which start at DC the time record resembles a digital oscilloscope display Signals at frequencies above the span have been filtered out Baseband time records are entirely real...

Page 203: ...FT2 where Avg is the averaging selected in the Average menu The cross spectrum contains both magnitude 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 is not required for vector averaging The magnitude is...

Page 204: ...rfect coherence to 0 0 no coherence Coherence measures the percentage of power in the response channel 2 which is caused by phase coherent with power in the reference or input channel 1 Ideally a coherence of 1 0 means that the corresponding transfer function 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...

Page 205: ...ss than half of the time record Cross Correlation Cross correlation is a two channel measurement In the time domain it is a comparison of a signal x t with a time shifted version of another signal y t τ displayed as a function of τ This is useful for measuring time delays between two common signals The definition of Cross Correlation depends upon the Average Mode selected in the Average menu Avera...

Page 206: ... 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 starts at DC are captured The capture buffer resembles a digital oscilloscope displa...

Page 207: ... Pan and Zoom functions in the Display Setup menu The capture buffer display will automatically pan as the capture fill and playback progress through the buffer During capture fill if the capture buffer contains more points than can be displayed points are skipped 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 co...

Page 208: ...ine spectrum is simply the measurement of a single channel over a sweep The spectrum is complex it contains phase and amplitude information The phase is relative to the source and is stable but arbitrary Single channel phase is not generally meaningful The spectrum measures the actual signal level at the inputs If source auto level is On then the spectrum will tend to be constant Use transfer func...

Page 209: ...surement data Each display has its own Measurement and each Measurement has an associated View Changing Measurements changes the View to the View associated with the new Measurement The two displays generally have different Measurements each with their own associated Views This entry field can be linked to the Measurement on both displays using the Link key Command VIEW d i The following Views are...

Page 210: ... In general single channel phase is useful only when the time record is triggered in phase with the signal For two channel measurements the phase is channel 2 relative to channel 1 Triggering is not generally required for meaningful two channel phase measurements Phase suppress sets the phase of small data values to zero This avoids the messy phase display associated with the noise floor Remember ...

Page 211: ...such as chirp source or swept sine The marker readout shows the real and imaginary parts of each point as well as its frequency The marker moves sequentially through the frequency points and can be linked to the frequency of the other display 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 compl...

Page 212: ...enter of the graph The center reference has the same units as the display The two displays can have different center reference values This entry field can be linked to both displays using the Link key Command YMID d x Y Min Set the Y Minimum bottom reference of the active display The bottom reference is the Y value of the bottom of the graph The bottom reference has the same units as the display T...

Page 213: ...the active display when the View is Nyquist or Nichols plot This value is the horizontal scale of the graph The knob adjusts the scale in a 1 2 5 10 sequence Changing the scale does not change the X Center location The X axis is scaled linearly and the scale is expressed in the display units The two displays can have different scales This entry field can be linked to both displays using the Link k...

Page 214: ...nt translations when expanded This entry field can be linked to both displays using the Link key Command XPAN d i Zoom Select the Zoom factor X axis expand of the active display Expand is shown in the display whenever it is expanded Expanding the X axis is a convenient way of examining closely spaced details in a display without changing the measurement Expansion is about the Marker Position whene...

Page 215: ...recalled 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...

Page 216: ...is disabled for the Octave Analysis and Swept Sine 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 DC bins are not shown The two displays can be scaled differently This entry field can be linked to both displays using the Link key Command XAXS d i Grid Select the ...

Page 217: ... displays using the Link key Command PSDU d i Transducer Convert Select the Transducer Conversion for the active display Acceleration Velocity Displacement Transducer Convert only has an effect for measurements of inputs with Transducer Units of acceleration velocity or displacement Transducer Convert is not available for Octave Analysis measurements Transducers such as accelerometers convert a ph...

Page 218: ...elow 60 dBV 1 0E 3 V set the threshold to 1 0E 6 V2 magnitude squared The two displays have their own Phase Suppress Threshold This entry field can be linked to both displays using the Link key Command PHSL d x d dx Window Set the d dx Window for the active display as a percentage of the display length 0 0005 10 The percentage is converted to a number of display bins minimum of 1 and the aperture ...

Page 219: ...s also available by choosing 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 di...

Page 220: ... 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 Distortion THD is calculated within the Marker menu in dB and ...

Page 221: ...nds 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 Powers Band Exclude can be used to remove a small band from a larger band ...

Page 222: ...g 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 vertical l...

Page 223: ...r 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 the other modes Each display has its own Normal Marker Rel Mode This entry field can be lin...

Page 224: ...et 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 key Command MROY d x X Rel Set the X Rel Mode for the Normal Marker of the a...

Page 225: ... 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 the Link key Command HRMN d i Display Select the Harmonic and Sideband Display for the ac...

Page 226: ...c 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 the Total Harmonic Distortion THD of the active display The THD squared is the harmonic power sum of the squared magnitudes of the ...

Page 227: ... 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 sideband fundamental separation is 1 etc The Sideband Marker identifies the carrier...

Page 228: ...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 Sideband Marker of the active display Absolute Relative The Marker Position Display shows the amplitude of the Fundamental or any ident...

Page 229: ...eband 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 Sideband Power is displayed in Vrms To convert to power square this result Command SPWR d i ...

Page 230: ...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 not included in band 2 Upper 2from1 means...

Page 231: ...le 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 top a...

Page 232: ......

Page 233: ...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 234: ...cted 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 broadband noise This source is useful for estimating transfer functions...

Page 235: ...de 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 trigger Continuous 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 ...

Page 236: ...4 54 Source Menu SR780 Network Signal Analyzer Command STYP i ...

Page 237: ... 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 238: ...ewidth 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 w...

Page 239: ...rom 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 x Burst Set the Burst Percentage of the chirp 0 1 100 The chirp waveform is output ...

Page 240: ...he 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 span of the chirp If the other display has a different span the chirp will not be app...

Page 241: ...ed 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 off at 3 dB oct providing equal energy per octave and extends beyond 102 kHz The spectrum of p...

Page 242: ...the Source Display FFT or the Source Period Octave 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 every source period Do not use Ch1 or Ch2 input trigger since the output will not start until a trigger is received Command NBUR x Source Display Select the Source Display Displa...

Page 243: ...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 Source trigger outputs a noise burst every source period Free Run Trigger...

Page 244: ...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 245: ... 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 246: ...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 247: ...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 248: ...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 249: ...el 1 or Channel 2 input Generally this is useful for transfer 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 transfer function The Auto Level Reference Channel determines which input will be maintained at the Ideal Reference Level This is usually the device under test o...

Page 250: ...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 251: ...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 252: ...e output or the device under test input range If the Reference Lower Limit requires a source amplitude greater than the Maximum Source Level then the source amplitude is set to the 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 ...

Page 253: ...is menu adjusts the input configurations for both inputs Playback uses the data stored in the capture buffer as the input for all measurements This selection is not valid until capture data has been acquired This menu sets the playback parameters Capture is not available for swept sine measurements Both displays use the same Input Source for their measurements The Analog Playback indicator shows t...

Page 254: ...onnects the shields to chassis ground with 50 Ω In this mode do not exceed 3 V on the shields The impedance between signal input and chassis ground is always 1 MΩ Command I1GD i Ch1 Coupling Select the Input Coupling for the Ch1 input DC AC ICP The Input indicator shows the current coupling at the top of the screen The 3 dB bandwidth of the AC coupling is 0 16 Hz ICP coupling connects a 5 mA curre...

Page 255: ...e changed while this HighV condition exists Command I2MD i Ch2 Grounding Select the Input Grounding for the Ch2 input shields Float Ground The shields of A and B are connected Float connects the shields to chassis ground through 1 MΩ 0 01 µF This allows the shield of a single ended input to float Ground connects the shields to chassis ground with 50 Ω In this mode do not exceed 3 V on the shields ...

Page 256: ...put Range for the Ch2 input 50 dBV 34 dBV The Input Range is the full scale signal input just before overload The Input Range varies by 2 dB steps The Input Range indicator shows the current range at the top of the screen Pressing this softkey turns off Ch2 Auto Range Command I2RG i ...

Page 257: ...emoving the filter can remove ringing and improve the accuracy of the time record The specifications apply only if the filter is On Command I1AF i Ch1 A Wt Filter Select the A Weighting Filter for the Ch1 input Off On The AWt indicator at the top of the screen shows AWt in bright whenever the A Weighting filter is On The A Weighting filter simulates the hearing response of the human ear and is oft...

Page 258: ...rally be left On Frequency domain measurements may have spurious alias signals if the filter is Off For time domain measurements involving square waves or impulses removing the filter can remove ringing and improve the accuracy of the time record The specifications apply only if the filter is On Command I2AF i Ch2 A Wt Filter Select the A Weighting Filter for the Ch2 input Off On The AWt indicator...

Page 259: ...t just those within the measurement span Command I2AR i Auto Offset Enable Auto Offset input calibration Off On When Auto Offset is On the analyzer 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 disrup...

Page 260: ...f inputs which are assigned units of acceleration velocity or displacement may be displayed with any of these three units using Transducer Convert in the Display Options menu Engineering Units Select Engineering Units for the Ch1 or Ch2 input On Off Measurements which require input data from a single input which has Engineering Units On will be displayed with units of EU Labels instead of Volts Th...

Page 261: ...rt The two displays have their own EU Label This entry field can be linked to both displays using the Link key Command EU1L i or EU2L i EU Volt Set the Engineering Units per Volt scale factor for the Ch1 or Ch2 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 ...

Page 262: ... use this feature for the other input channel In this case the active display is not affected but other measurements based upon the other input are affected User Label Enter the User Label for the Ch1 or Ch2 input Engineering Units Use the ALT keys for alphabetic entry to enter a user defined name for the engineering units The displayed units change from Volts to the User Label when Engineering Un...

Page 263: ... bins are separated by a time equal to 1 Capture Sampling Rate The 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 bu...

Page 264: ... 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 265: ...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 266: ...4 84 Playback Input Menu SR780 Network Signal Analyzer ...

Page 267: ...d run continuously or until they are complete Auto Arm enables triggering whenever measurements are running with Start Reset For FFT measurements auto arming means that as soon as both time records are processed the trigger is immediately re armed Time records are taken as fast as the trigger delay and time record processing permit Two FFT measurements are always triggered together Manual Arm enab...

Page 268: ... External Ext TTL and Manual also trigger the burst Chirp and Noise source waveforms Source triggers synchronously with the source waveform The source runs continuously and Source Trigger synchronizes the time record with the source waveform Source Trigger is not valid for swept sine measurements For FFT measurements the phase of signals which are synchronous with the trigger is stable Vector aver...

Page 269: ...r each record time record length plus trigger delay is noticeably long Auto Arm Trigger Mode re arms the trigger after both FFT displays have completed processing their time records Command TDLA i Delay B Set the Trigger Delay for DisplayB 8000 100000 The Trigger Delay applies only to FFT measurements The Trigger Delay is specified in samples 1 sampling rate of the time record The triggered time r...

Page 270: ...ource period or arbitrary source length This is useful when the source length is the same as the FFT time record length Do not use Ch1 or Ch2 input trigger since the output will not start until a trigger is received Source trigger outputs the source continuously over and over FFT time records are synchronized to the source start Watch Out For Triggered Sources If a triggered source is selected Chi...

Page 271: ...Manual Trigger Source requires Manual Trigger or an interface command to trigger Use Auto Arm Trigger Mode with since unwanted triggers are not a problem For FFT measurements each time record requires a trigger For octave and swept sine measurements the first trigger after arming starts the measurement and subsequent triggers are ignored Command TMAN ...

Page 272: ...4 90 Trigger Menu SR780 Network Signal Analyzer ...

Page 273: ...together improves accuracy and repeatability Averaging Select Averaging for the active display Off On Many FFT measurements have averaging as part of their definition Transfer Function Coherence Auto Correlation and Cross Correlation In these cases the effect of averaging depends upon the exact measurement If the measurement is Coherence averaging is always on regardless of this menu Time records ...

Page 274: ... is On changing the Averaging Mode resets the average and starts the new average immediately without pressing the Start Reset key Each display has its own Averaging Mode This entry field can be linked to both displays by using the Link key Command FAVM d i RMS Averaging RMS averaging computes the average of the real part X and imaginary part Y of a measurement according to Xavg sqrt mean X2 and Ya...

Page 275: ...nals of interest have stable relative phases triggering is not required for vector averaging Triggering is still required to isolate time records which contain the signals of interest The Time Record Increment is ignored whenever the measurement is vector averaged Overlap processing is not allowed in this case and 100 increment is used Peak Hold Averaging Peak Hold is not really averaging rather t...

Page 276: ... stopping Each completed average counts as a single waterfall record Exponential Weighting Exponential weighting weights new data more than old data For RMS and Vector averaging weighting takes place according to the formula Average N New Data 1 N Average N 1 N 1 N where N is the Number Of Averages While Exponential averaging is in progress the number of averages completed is shown in the Horizont...

Page 277: ...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 When the Time Record Increment 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 s...

Page 278: ...AND after the measurement was unsettled These unsettled measurements are displayed in half intensity indicating that 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 inc...

Page 279: ... Preview is Timed the input time record is automatically accepted after the Preview Time unless rejected first The preview time records are displayed in place of the actual measurements For single channel measurements the appropriate channel input time record is shown in each display For 2 channel measurements the DisplayA shows Ch1 time record and DisplayB shows Ch2 time record In this case use t...

Page 280: ...rejecting bad time records from corrupting an averaged measurement Command PAVA Reject Reject the displayed preview time record and do not 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 ave...

Page 281: ...d separately 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 displ...

Page 282: ... 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 283: ...raging Type is not Peak Hold Total Impulse and L may 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 Pea...

Page 284: ... 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 When the Trigger Mode is Free Run a linear averaged measurement starts with Start Reset and finishes when the Integration Time is complete The next measurement does not start until Start Reset is p...

Page 285: ...eep 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 allowed ...

Page 286: ...isplayed 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 number of Integration Cycles 1 32767 At each frequency point the inputs measure the signal at the source frequency This is done by mult...

Page 287: ...e 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 288: ...4 106 Swept Sine Average Menu SR780 Network Signal Analyzer ...

Page 289: ...nction is selected as the Measurement for a display the View and Units need to know how to compute dB from the dimensionless measurement data If the function has linear units e g FFT FFT then 20log should be used If the function has squared units e g Octave or FFT FFT then 10log should be used Auto chooses 10log if any operand in the function is naturally a squared measurement These include Cohere...

Page 290: ... exit this menu Enter Eq will enter the new function equation and exit this menu The new User Function definition is used immediately if it is being displayed Command USRF i j k l m FFT Group Command USRO i j k l m Octave Group Command USRS i j k l m Swept Sine Group Operands Use the knob to pick one of the displayed Operands and press Enter to place it in the equation at the cursor location The d...

Page 291: ...measurements FFT 1 and FFT 2 are the FFT of the Ch1 and Ch2 inputs These operands use the window chosen in the Window menu for the display which is measuring the function FFTa 1 is the FFT of the Ch1 input using the window for Display A regardless of which display is measuring the function FFTb 2 is the FFT of the Ch2 input using the window for Display B This allows a function to be defined which ...

Page 292: ...e shared 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 Octave Measurement Gr...

Page 293: ...lts are always averaged so the Avg and VecAvg operators are also not required FFT FFTu IFFT Avg and VecAvg are only available in the FFT Measurement Group FFT is the windowed FFT operator These operations switch the X axis type The current window chosen in the Window menu is used on the operand before the FFT FFTu is the un windowed FFT operator The uniform window is always used The FFT and FFTu o...

Page 294: ...ve the highlighted cursor within the equation Delete will delete the highlighted term Operands and Operations will either insert or replace at the cursor Use Insert Replace to switch between insert and replace mode Backspace deletes the term before the cursor Insert Replace Toggle between insert and replace mode while editing a User Function equation If editing in insert mode Ins appears in the up...

Page 295: ...t Display the Edit Constant menu Press Return or User Math for the main User Math menu Constants may be used as operands in a User Function There are 5 constants which may be defined and are shared by all Measurement Groups Command USRC i x y Constant Use the knob to pick one of the five Constants to edit and press Enter Real Part Enter a new value for the real part of the selected Constant The im...

Page 296: ...er 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 shown in the Marker Position Bar of the active display to the magnitude of the selected Constant No unit translation takes place Make sure that the units of the active display are correct before using this fea...

Page 297: ... 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 Hanning The Hanning window is the most commonly used window However it has an amplitude variation of about 1 5 dB for off bin signals and provides only reasonable selectivity Its side lobes are very high a...

Page 298: ...often used in impact testing on the response channel to remove oscillations which last longer than the time record Force Exponential Many impact measurements require the Force window for one channel and the Exponential window for the other channel Use User Math to define a 2 channel measurement using different windows for each input channel For example to measure a transfer function with a force w...

Page 299: ...dified Points in the time record past the Force Length are zeroed Choose Force as the FFT window before setting the Force Length The two displays can have different Force Lengths This entry field can be linked to both displays by using the Link key Command FWFL d i Expo TC Set the Expo Window Time Constant as a percentage of the FFT time record 5 1000 This is the point where the window function re...

Page 300: ...ick 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 active display User window Non Symmetric Symmetric Use Symmetric if the User window ...

Page 301: ...n 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 is scrolls down and the newest record is added to the top back While running the display may not update fast enough...

Page 302: ...splay 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 stores the Total Count number of measurement records and pauses the waterfall storage The first Total Count number of records are saved in memory The measurement in the other display...

Page 303: ...Total Count This entry field can be linked to both displays by using the Link key Command WTOT d i Skip Storage Interval Set the Waterfall Skip Storage Interval for the active display The rate at which measurement records are added to waterfall memory is set by the Skip Storage Interval This allows the waterfall memory to hold a longer time history as well as setting a variable storage rate The in...

Page 304: ... display and should be less than the Total Count in order to use the display are 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 A large View Count is a good way to display an overview of the entire buffer in order to identify a regi...

Page 305: ...d WANG d i Allocate Memory Display the Memory Allocation menu Total Available Displays the total memory available for storage either 992 2016 or 4066 blocks depending upon the amount of installed memory Each block is 2 kPoints 2048 points The total of the Capture Waterfall and Arbitrary memory allocations cannot exceed the Total Available memory It may be necessary to decrease one allocation in or...

Page 306: ... 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 Trace saves the record selected by the marker to a Trace Command MWFL d i More Display the More Waterfall menu Press Return or Waterfall for the main Waterfall menu Fast An...

Page 307: ...ont of the display New records which appear at the top are behind the older records Invisible Hidden Lines will remove the portions of the new record which are behind older records This cleans up a waterfall display by removing intersecting lines If records at the front of the waterfall are obscuring details hidden behind them reverse the waterfall direction Each display has its own Waterfall Hidd...

Page 308: ...e 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 complete the operation The stored slice contains as many points as were stored in the Waterfall buffer up to Total Count The points in a slice trace are numbered and displayed from 0 data from ...

Page 309: ...will be half as long as for a single input 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 the Capture Mode...

Page 310: ...um sampling rate is 262 1 kHz when the FFT Base Frequency is 102 4 kHz and 256 kHz when the FFT Base Frequency is 100 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 the...

Page 311: ...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 Arb Memory allocates memory blocks for the Arbitrary Source waveform The Arbitrary Source can also use the capture buffer as the output waveform Command MALC i j k Confirm Allocation Confirm Allocation places the new memory allocations into e...

Page 312: ...t 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 the buffer During playback this keeps the capture display showing the points which are currently being measured Off leaves the display Pan to that set in the Display Setup menu Command CPAN i ...

Page 313: ...uency 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 exceeds ...

Page 314: ...e display The accumulation of the statistical quantities continues 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...

Page 315: ...his key has no effect unless the Data Table 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 Delete Line Delete the...

Page 316: ...4 134 Data Table Analysis Menu SR780 Network Signal Analyzer 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 317: ... 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 Command L...

Page 318: ...egment 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 end points These markers a...

Page 319: ...ay 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 Enter or adjust the X coordinate for the Current Segment End point The X coordinates are assumed to be in th...

Page 320: ...t Testing Analysis Menu SR780 Network Signal Analyzer 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 321: ...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 322: ...ay 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 value for display A since Marker Stats was turned On or Reset This...

Page 323: ...ay 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 value for display B since Marker Stats was turned On or Reset This...

Page 324: ...ly 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 starts at the start index and includes all records through the stop in...

Page 325: ... which are analyzed is specified 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 result is stored in a data trac...

Page 326: ...144 Exceedance Statistics Menu SR780 Network Signal Analyzer ...

Page 327: ...h the knob and press Enter to make it the Current File Name This file name is used for saving and 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 c...

Page 328: ...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 when data is recalled to it The display will not update with live measurement results until the Display is set back to Live in the Display Options menu The measurement frequency span averaging and window are recalled with the data ...

Page 329: ... to save it to disk Only traces which currently have data in them may be selected To save a display to a Trace use Display to Trace Alt Print Screen Command TSAV i Disk to Trace Recall data from the Current File in the Current Directory to a Trace 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 recall from disk to...

Page 330: ...0 Network Signal Analyzer 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 331: ...ode where the stimulus is applied The name may be up to six characters long The SR785 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 SR785 files into formats suitable for modal analysis programs Command RFNA s Reference Number Enter the identification for the reference node For ...

Page 332: ...r use by external programs which convert the SR785 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 SR785 does not use t...

Page 333: ...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 334: ...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 335: ...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 336: ...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 337: ...tered 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 is specified The default extensions should be used since the directory display assumes an extensi...

Page 338: ...I 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 Vpk The first value in the file is N followed by the real part of the first point then the imaginary part of the first point etc Each value is delimited by a comma white space tab or ...

Page 339: ...librate live measurements The target trace must already store data of the type and length to be loaded from disk The file only contains data points no measurement information is recalled The recalled data simply takes the place of the stored trace data and assumes the trace s measurement parameters Measurement Averaging Window Frequency span and length The binary file contains N complex points Eac...

Page 340: ... capture buffer can be loaded into the arbitrary waveform buffer and vice versa Interval Choose to save the entire data buffer or only the playback portion Capture or Arbitrary Waveform All stored waterfall records for both displays are saved This only affects the saving of data to disk When a buffer is loaded from disk the buffer is configured to be exactly the length of the recalled data Disk to...

Page 341: ...n 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 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...

Page 342: ... point Each waterfall buffer contains a number of records For example if both displays have stored 250 400 line FFT s in the waterfall buffer the disk space required to save the entire buffer is 512 pts in FFT x 2 floats per complex pt x 250 stored records x 2 both displays 512 000 bytes If more space is required than is available on disk the buffer save will require multiple disks At each disk pr...

Page 343: ...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 344: ... 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 345: ...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 346: ...patible 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 screen for the Bitmap Pri...

Page 347: ...rt 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 interface Most HPGL plotters use this Command PDST i GPIB Control Choose the GPIB Controller Host or...

Page 348: ...he 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 position of the Note with the knob Command NOTE i j k l m s Text Y Position Adjust the vertical position of the Note with the knob ...

Page 349: ...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 SCRNXXXX EXT where XXXX is a 4 digit number which automatically increments starting at the File Start Number Command PFIL i Colors Display the Hardcopy Colors menu Press Return or Output for the ...

Page 350: ...th black or gray Command PBLK i Print Graph Select the graph print mode Black on White White on Black The graph is normally printed as Black data and grid on White background This uses the least printer ink Choosing White data and grid on Black background prints a large black area on the paper Command PGRF i Plot Color Selections Many plotters have a multipen carousel In this case different items ...

Page 351: ...gnal Analyzer Plotter Trace Pen Assign a plotter pen number to the graph data trace 1 to 8 Command PLTR i Plotter Marker Pen Assign a plotter pen number to the graph marker 1 to 8 Turn the marker off to avoid plotting it Command PLMK i ...

Page 352: ...4 170 Output Menu SR780 Network Signal Analyzer ...

Page 353: ...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 354: ...red 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 Control and Number keys and Special Keys will either insert or replace at the c...

Page 355: ...R780 Network Signal Analyzer 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 356: ...PIB 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 to from REMOTE to LOCAL front panel en...

Page 357: ...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 SR780 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 Queu...

Page 358: ...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 359: ...een 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 determining the exact frequency of a bin R...

Page 360: ...ters 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 the disk file and is used when translat...

Page 361: ...rs 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 362: ...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 363: ...eturn 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 Return for the Memory ...

Page 364: ...ial 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 store the serial numb...

Page 365: ...al Keys 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 Backsp...

Page 366: ...a parameter 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 Mac...

Page 367: ...ormal 5 39 Marker Commands Harmonic 5 41 Marker Commands Sideband 5 42 Marker Commands Band 5 43 Source Commands 5 44 Sine Source Commands 5 45 Chirp Source Commands 5 46 Noise Source Commands 5 47 Arbitrary Source Commands 5 48 Swept Sine Source Commands 5 49 Input Commands 5 51 Input Playback Commands 5 54 Trigger Commands 5 55 Average Commands FFT 5 56 Average Commands Octave 5 58 Average Comma...

Page 368: ...easurement Frequency Swept Sine Measurement Group SSTR d f 5 29 Swept Sine Start Frequency SSTP d f 5 29 Swept Sine Stop Frequency SSFR 5 29 Swept Sine Progress SRPT d i 5 29 Swept Sine Repeat Mode SSTY d i 5 29 Swept Sine Sweep Type SARS d i 5 29 Swept Sine Auto Resolution SNPS d i 5 30 Swept Sine Number of Points SSKP d i 5 30 Swept Sine Max Step Size SFST d x 5 30 Swept Sine Faster Threshold SS...

Page 369: ...rker to the Maximum MKMN d 5 38 Move the Marker to the Minimum MKCN d 5 38 Center of FFT Span to Marker Normal Marker MSEK d i 5 39 Normal Marker Seeks Mode MWID d i 5 39 Normal Marker Width MREL d i 5 39 Normal Marker Relative Mode MROX d x 5 39 Normal Marker X Offset MROY d x 5 39 Normal Marker Y Offset MXRL d i 5 39 Normal Marker X Rel Mode MRON d 5 39 Set Marker to Ref Harmonic Marker HRMN d i...

Page 370: ... Source Amplitude ARAT i 5 48 Arbitrary Source Rate ASRC i 5 48 Arbitrary Source Buffer ASTR i 5 48 Arbitrary Source Start ALEN i 5 48 Arbitrary Source Length TARB i 5 48 Trace to Arb ALOD n 5 94 Download Arbitrary Binary AGET i 5 96 Upload Arbitrary Buffer APUT i 5 96 Download Arbitrary Buffer Swept Sine Source Swept Sine Measurement Group SSAL i 5 49 Swept Sine Auto Level SSAM x 5 49 Swept Sine ...

Page 371: ...U s 5 53 Ch2 User Label INPC i 5 106 Input Ovld Read Input Playback ISTR i 5 54 Capture Playback Start ILEN i 5 54 Capture Playback Length IMOD i 5 54 Capture Playback Mode ISPD i 5 54 Capture Playback Speed Trigger TMOD i 5 55 Trigger Mode TSRC i 5 55 Trigger Source TLVL i 5 55 Trigger Level TSLP i 5 55 Trigger Slope TDLA i 5 55 Trigger Delay A TDLB i 5 55 Trigger Delay B TARM 5 55 Manual Trigger...

Page 372: ...e Length FWTC d i 5 63 FFT Expo TC TRWI d i 5 63 Trace i to Window WITR d i 5 64 Window to Trace i WSYM d i 5 64 Window Form Waterfall FFT Octave Measurement Group WDSP d i 5 65 Waterfall Display WSTO d i 5 65 Waterfall Storage WAVA d 5 65 Waterfall Records Stored WTOT d i 5 65 Waterfall Total Count WFSK d i 5 65 Waterfall FFT Skip WOSK d x 5 65 Waterfall Octave Skip WVCT d i 5 65 Waterfall View C...

Page 373: ...ent LSEG d i j x0 y0 x1 y1 5 72 Set Limit Segment i LDLT d i 5 73 Delete Limit Segment LSFT d x 5 73 Shift Limit Segments Marker Statistics MSAO d i 5 74 Marker Statistics On MSRS 5 74 Reset Marker Statistics MSAA 5 74 Marker Max A Read MSIA 5 74 Marker Min A Read MSEA 5 74 Marker Mean A Read MSSA 5 74 Marker Std Dev A Read MSAB 5 74 Marker Max B Read MSIB 5 74 Marker Min B Read MSEB 5 74 Marker M...

Page 374: ...lot Screen PLTP i 5 80 Vector Plotter Type PLTA i 5 80 Plotter GPIB Address PCIC i 5 80 GPIB Control PLTX i 5 80 Plotter Text Pen PLGD i 5 80 Plotter Grid Pen PLTR i 5 80 Plotter Trace Pen PLMK i 5 80 Plotter Marker Pen NOTE i j k l m s 5 80 Display Note System OUTX i 5 82 Output Remote Interface OVRM i 5 82 Overide Remote KCLK i 5 82 Key Click ALRM i 5 82 Alarms On ALRT i 5 82 Alarms Volume ADON ...

Page 375: ... 78 Trace i to Disk TRCL i 5 78 Disk to Trace i TLOD i n 5 92 Download Trace i Binary TASC i n 5 93 Download Trace i Ascii TGET i 5 95 Upload Trace i Buffer TPUT i 5 95 Download Trace i Buffer Data Transfer DSPN d 5 89 Display d Length DSPY d j 5 89 Read Display d bin j ASCII DSPW d i j 5 89 Read Waterfall d Record i bin j ASCII REFY d j 5 89 Read Ref Display d bin j DSPB d j 5 89 Read Display d B...

Page 376: ...Response Node Name RSNU i 5 103 Response Node Number Status CLS 5 104 Clear All Status Registers PSC i 5 104 Power On Status Clear SRE i j 5 104 Serial Poll Status Enable STB i 5 104 Serial Poll Status Read ESE i j 5 104 Standard Event Status Enable ESR i 5 105 Standard Event Status Read ERRE i j 5 105 Error Status Enable ERRS i 5 105 Error Status Read INSE i j 5 105 Instrument Status Enable INST ...

Page 377: ...load Arbitrary Binary ALRM i 5 82 Alarms On ALRT i 5 82 Alarms Volume AOVL i 5 82 Audible Overload APUT i 5 96 Download Arbitrary Buffer ARAT i 5 48 Arbitrary Source Rate ASCL d 5 85 AutoScale ASRC i 5 48 Arbitrary Source Buffer ASTR i 5 48 Arbitrary Source Start B BEXC d i 5 43 Band Exclude BMKL d i j 5 43 Band i Left Bin j BMKR d i j 5 43 Band i Right Bin j BPWR d i 5 43 Band Power BRAM d i 5 43...

Page 378: ...SWB d i j 5 91 Read Display d Waterfall Record i Binary DTBL d i 5 70 Data Table On DTRD d i 5 71 Data Table Query DUMP 5 79 Dump Display Data E EPCT i 5 75 Exceed Centile ERRE i j 5 105 Error Status Enable ERRS i 5 105 Error Status Read ESTP i 5 75 Exceed Stop Index ESTR i 5 75 Exceed Start Index EU1L i 5 52 Ch1 EU Label EU1M i 5 52 Ch1 Engineering Units Off On EU1U s 5 53 Ch1 User Label EU1V x 5...

Page 379: ... 5 41 Number of Harmonics HTHD d i 5 41 Query the Total Harmonic Distortion I I1AF i 5 51 Ch1 Anti Alias Filter I1AR i 5 51 Ch1 AutoRange Mode I1AW i 5 51 Ch1 A Weight Filter I1CP i 5 51 Ch1 Input Coupling I1GD i 5 51 Ch1 Input Grounding I1MD i 5 51 Ch1 Input Mode I1RG i 5 51 Ch1 Input Range I2AF i 5 52 Ch2 Anti Alias Filter I2AR i 5 52 Ch2 AutoRange Mode I2AW i 5 52 Ch2 A Weight Filter I2CP i 5 5...

Page 380: ...ve the Marker to the Minimum MKMX d 5 38 Move the Marker to the Maximum MMEM 5 69 Total Memory Available MREL d i 5 39 Normal Marker Relative Mode MRKB d 5 37 Query the Marker Bin MRKR d i 5 37 Marker Tracking MRKX d 5 37 Query the Marker X Position MRKY d 5 37 Query the Marker Y Position MRKZ d 5 38 Marker Z Read MRON d 5 39 Set Marker to Ref MROX d x 5 39 Normal Marker X Offset MROY d x 5 39 Nor...

Page 381: ...eride Remote P PAUS 5 84 Pause PAVA 5 57 Accept Preview PAVO d i 5 57 Average Preview PAVR 5 57 Reject Preview PAVT d x 5 57 Preview Time PBLK i 5 80 Print Black PBRI i 5 79 Print Bright PCIC i 5 80 GPIB Control PDIM i 5 80 Print Dim PDST i 5 79 Print Plot Destination PFIL i 5 79 File Start Number PGRF i 5 80 Print Graph PHSL d x 5 36 Phase Suppress Threshold PLAY i 5 88 Play Tune PLGD i 5 80 Plot...

Page 382: ...ept Sine Number of Points SPWR d i 5 42 Query the Sideband Power SRAT x 5 49 Swept Sine Ramp Rate SRCL i 5 77 Recall Settings SRCO i 5 44 Source On Off SRMP i 5 49 Swept Sine Source Ramping Off On SRPT d i 5 29 Swept Sine Repeat Mode SSAL i 5 49 Swept Sine Auto Level SSAM x 5 49 Swept Sine Amplitude SSAV 5 77 Settings to Disk SSCY d i 5 60 Swept Sine Settle Cycles SSEP d f 5 42 Sideband Separation...

Page 383: ... i j k l 5 61 FFT User Function i USRO i j k l 5 61 Octave User Function i USRS i j k l 5 61 Swept Sine User Function i V VIEW d i 5 32 Display View W WANG d i 5 66 Waterfall Angle WAVA d 5 65 Waterfall Records Stored WDSP d i 5 65 Waterfall Display WFSK d i 5 65 Waterfall FFT Skip WFST d i 5 66 Waterfall Fast Angles WGET 5 98 Upload Waterfall Buffer WHID d i 5 66 Waterfall Hidden Lines WHIT d i 5...

Page 384: ...al Analyzer XDIV d x 5 34 X Division Polar XPAN d i 5 34 X Pan XZOM d i 5 34 X Zoom Y Y2DV d x 5 34 Y Division Polar YCEN d x 5 34 Y Center Polar YDIV d x 5 34 Y Division YMAX d x 5 33 Y Maximum YMID d x 5 33 Y Midpoint YMIN d x 5 33 Y Minimum ...

Page 385: ... an input that is used to control the SR780 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 SR780 has 4 interface indicators which are displayed at the top of the screen The RS2...

Page 386: ...ed by querying the SR780 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 SR780 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 multiple query commands are sent on one command line separated by semicolons of course the ...

Page 387: ... 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 sending the ERRS query Data Synchronization Changing measurement parameters often invalidates the ...

Page 388: ...easons the function is specifically not allowed in the current measurement context or the function is only applicable for certain measurement groups For example FFT Start Frequency is grayed when the measurement is full span The FSTR set command is not allowed in this situation However the FSTR query command is still allowed An example of group specific parameter are the commands which set Swept S...

Page 389: ... The query returns the value of these parameters 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...

Page 390: ... DisplayB 1 or Both Displays 2 without regard to the active display or any parameter linking Active display and linking are screen features which do not apply to interface commands Command Context Errors Commands which perform softkey functions are not allowed unless the corresponding softkey function is allowed If the softkey is not available either shown in gray or not displayed at all then the ...

Page 391: ...s 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 The set command requires at least one display to be Live FSTR d f The FSTR command sets queries the FFT Start frequency ...

Page 392: ... 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 settled The measurement is unsettled by changing any one of several measurement parameters For example changing the input range or FFT span will unsettle the measurement If the signal comes from an...

Page 393: ... 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 i The OCHN command sets queries the Octave Channels The parameter i selects 1 0 or 2 1 channel octave analysis ...

Page 394: ...5 28 Frequency Commands SR780 Network Signal Analyzer This command is valid only when the Measurement Group is FFT or Octave ...

Page 395: ...ress 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 display d The parameter i selects Sing...

Page 396: ... 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 397: ...lay d to be Live 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 command requires display d to be Live F...

Page 398: ... 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 command sets queries the View of display d The parameter i selects the view from the list below Each view has associated units Changing the View changes the Units to the units last used with the new view ...

Page 399: ...fer Function and Coherence are unitless so only dB and Units are available Phase and Unwrapped Phase must select either degrees or radians 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 YMAX d x The YMAX command sets queries the Y Maximum top reference of display d The pa...

Page 400: ... change the X Center value Always use the XCEN command after the XDIV command YCEN d x The YCEN command sets queries the Y Center 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 Y2DV d x The Y2DV command sets queries the polar Y Division scale of display d The parameter x is a real number in the display units This co...

Page 401: ... command to select the active display in the Single format In the Single format the inactive display is still accessible via commands XAXS d i The 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 ...

Page 402: ...in DBMR x The DBMR command sets queries the dBm Reference Impedance for BOTH displays The parameter x is a real value of Ohms This affects the calculation of dBm units in both displays PHSL d x The PHSL command sets queries the Phase Suppress Threshold 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 q...

Page 403: ...e 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 command is valid only if display d is a Waterfall and the measurement is paused This c...

Page 404: ...s 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 performs Marker to Min on display d...

Page 405: ...l 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 MXRL d i The MXRL command sets queries the X Rel Mo...

Page 406: ...5 40 Marker Commands SR780 Network Signal Analyzer 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 407: ...aximum 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 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 H...

Page 408: ...y 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 display...

Page 409: ...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 BEXC 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 410: ... 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 411: ... This command is valid only when the Source Type is Sine SOFF x The SOFF command sets queries the Offset of the Sine Source The parameter x is a real number of V This command is valid only when the Source Type is Sine S2FR f The S2FR command sets queries the Frequency of Sine Tone 2 The parameter f is a frequency in Hz This command is valid only when the Source Type is Sine S2AM x The S2AM command...

Page 412: ...pe 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 CSRC i The CSRC command sets queries the Source Display The parameter i selects DisplayA 0 or DisplayB 1 This command is valid only when the Source Type is Chirp or Noise and the Measureme...

Page 413: ... 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 NPER x 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 valid only when the Source Type is Noise and the Measurement Group is Octave ...

Page 414: ...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 415: ...uto 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 command is valid only when the Measurement Group is Swept Sine SRAT x The SRAT command sets queries the Swept Sine Source Ramp Rate The parameter x is ramp rate in V s This command is valid only when the Measurement Group is Swept Sine SSUL x The SSUL comm...

Page 416: ...work Signal Analyzer SMAX x The SMAX command sets queries the Swept Sine Maximum Level The parameter x is a real number of mV This command is valid only when the Measurement Group is Swept Sine and Auto Level Reference is Ch1 or Ch2 ...

Page 417: ...and must be even If Ch1 AutoRange is On the I1RG i command will turn Ch1 AutoRange Off and set the Ch1 Range to i A1RG i The A1RG command sets queries the Ch1 AutoRanging Off On The parameter i selects Off Manual 0 or On AutoRanging 1 If i 1 and Ch1 AutoRange is already On a new AutoRange is performed I1AR i The I1AR command sets queries the Ch1 AutoRange Mode The parameter i selects Normal 0 or T...

Page 418: ...elects Off Manual 0 or On AutoRanging 1 If i 1 and Ch2 AutoRange is already On a new AutoRange is performed I2AF i The I2AF command sets queries the Ch2 Anti Aliasing Filter Off On The parameter i selects Off 0 or On 1 I2AW i The I2AW command sets queries the Ch2 A Weighting Filter Off On The parameter i selects Off 0 or On 1 IAOM i The IAOM command sets queries the Input Auto Offset Off On The pa...

Page 419: ...s the Ch2 Engineering Units Mode The parameter i selects Off 0 or On 1 EU2L i The EU2L command sets queries the Ch2 Engineering Units Label The parameter i selects the unit label i Label i Label 0 m s2 8 kg 1 m s 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 EU2V x The EU2V command sets queries the Ch2 Engineering Units per Volt scale The parameter x is real number of ...

Page 420: ...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 421: ...igger Slope The parameter i selects Rising 0 or Falling 1 TDLA i The TDLA command sets queries the Trigger Delay A The parameter i is a number of samples from 8000 to 100000 This command is valid only when the Measurement Group is FFT TDLB i The TDLB command sets queries the Trigger Delay B The parameter i is a number of samples from 8000 to 100000 This command is valid only when the Measurement G...

Page 422: ...n the Measurement Group is FFT The set command requires display d to be Live FAVN d i The FAVN command sets queries the FFT 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 The set command requires display d to be Live NAVG d The NAVG command queries the Number of Averages completed for display d F...

Page 423: ...clude 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 been acquired After accepting or rejecting the time record the display reverts back to showing the actual measurement 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 ...

Page 424: ...eted 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 Averaging...

Page 425: ...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 426: ... 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 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 Sine The s...

Page 427: ...and S indicate in which measurement groups each token is valid FFT Octave Swept Sine 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 O S Conj 102 F O S Real 103 F O S Imag 104 F O S Ln 105 F O S Exp 106 F O S FFT 107 F FFTu 108 F IFFT 109 ...

Page 428: ...F2 F1 74 F X_Spec 77 F FFT2 FFT1 78 F X_Spec 75 S Trans_Fn 76 S Trace1 41 F O S Trace2 42 F O S Trace3 43 F O S Trace4 44 F O S Trace5 45 F O S Const1 51 F O S Const2 52 F O S Const3 53 F O S Const4 54 F O S Const5 55 F O S j 60 F O S 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 a...

Page 429: ...ent Group is FFT The set command requires display d to be Live FWFL d i The FWFL command sets queries the FFT Force Window Length for display d The parameter i is a percentage of the time record from 1 to 100 This command is valid only when the Measurement Group is FFT The set command requires display d to be Live FWTC d i The FWTC command sets queries the FFT Expo Window Time Constant for display...

Page 430: ...race i Trace i will have a length of 2048 points This command is valid only when the Measurement Group is FFT WSYM d i The WSYM sets queries User Window Form for display d The parameter i selects Non Symmetric 0 or Symmetric 1 This command is valid only when the Measurement Group is FFT and the window of display d is User ...

Page 431: ...e Measurement Group is FFT or Octave WAVA d The WAVA command queries the number of records available in the waterfall buffer for display d Records are not stored in the buffer unless Waterfall Storage is on Continuous or One Shot This command is valid only when the Measurement Group is FFT or Octave WFSK d i The WFSK command sets queries the Waterfall Skip count for FFT measurements for display d ...

Page 432: ...hold for display d The parameter i is a percentage of the full scale trace height This command is valid only when the Measurement Group is FFT or Octave WHID d i The WHID command sets queries the Waterfall Hidden Lines for display d The parameter i selects Invisible 0 or Visible 1 This command is valid only when the Measurement Group is FFT or Octave WREV d i The WREV command sets queries the Wate...

Page 433: ...Commands 5 67 SR780 Network Signal Analyzer This command is valid only when the Measurement Group is FFT or Octave and the measurement is paused with waterfall storage on If there is no bin j then an error occurs ...

Page 434: ...er from 2 to the maximum allocated memory This command is valid only when the Measurement Group is FFT or Octave and the Input Source is Analog and the Source is not Arbitrary playback from Capture 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 t...

Page 435: ...aterfall 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 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 436: ...a 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 line i Bin 0 is the leftmost bin in the display If there is no bin j in ...

Page 437: ...rned 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 current measurement span the values 1 0E 34 are returned for both X and Y ...

Page 438: ...ter 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 LMAX d i command sets the last limit segment number to...

Page 439: ...ints 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 displays This command also sets Limit Segments to Show LS...

Page 440: ...t 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 Dev...

Page 441: ...er than the number of records stored in the waterfall buffer minus one This command is valid only when the Measurement Group is FFT or Octave 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 valid only when the Measurement Group is FFT or Octave EXCE d i The EXCE command starts the exceedance centile calculation...

Page 442: ...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 443: ...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 444: ...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 445: ...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 disabled until printing is completed PRTP i The PRTP command sets qu...

Page 446: ...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 selects Host 0 or SR780 1 PLTX i The PLTX command sets queries the Plotter Text Pen Number The parameter i is a pen number from 1 to 8 PLGD i The PLGD command sets queries the Pl...

Page 447: ...k Signal Analyzer 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 448: ...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 449: ... 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 450: ...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 required before the status returns to settled The measu...

Page 451: ...e 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 separately d 2 is not allowed A1RG i The A1RG command sets queries the Ch1 AutoRanging Off On The parameter i selects Off Manua...

Page 452: ...nd 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 The SNAP command rescales the Reference Display of display d to the curren...

Page 453: ...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 454: ...elects 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 SR780 s pre programmed sounds The parameter i selects a sound from 0 to 6 most ...

Page 455: ...ts 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 measurement or take the display Off Line The returned data depen...

Page 456: ...ered from 0 to length 1 The value is returned as an ASCII real number The returned data depends upon the display View and Units The data values are the same as if they were read with a marker DSPB d j The DSPB d command returns the data in display d in binary format The parameter d selects Display A 0 or Display B 1 This command is only available with the GPIB interface The DSPB d j command return...

Page 457: ...E float The DSWB d i command returns all of the data in record i in binary format Do not serial poll for IFC bit 7 in the Serial Poll status after DSWB is sent IFC will NOT be set until the transfer is complete Send the command and then make the host computer a listener and the SR780 a talker The DSWB d i returns 4 bytes per bin starting with bin 0 and continuing to bin length 1 There is no separa...

Page 458: ...s in the trace NOT the data displayed in a particular view Remember views are simply different ways 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 Trace Type n FFT Coherence CrossSpec Transfer Function 100 FFT lines 128 1st 101 points displayed 200 FFT lines 256 1st 201 points displayed 400 FFT lines 512 1st ...

Page 459: ...st On receipt of 1 4 byte binary long int executes a binary transfer to the SR780 of 2n 4 byte IEEE floats The order is real part of point 0 imag part of point 0 real part of point 1 imag part of point 1 etc Each 4 byte float is transmitted least significant byte first A total of 8n bytes are transferred Assert EOI with the final byte of the transfer Serial Poll until IFC bit 7 is set in the Seria...

Page 460: ...real part of point 0 imag part of point 0 real part of point 1 imag part of point 1 etc Each ASCII float is delimited by a comma space tab or carriage return NOT EOI Assert EOI with the final byte of the transfer Serial Poll until IFC bit 7 is set in the Serial Poll status before sending another command ALOD n The ALOD command loads binary data into the Arbitrary Waveform buffer This command is va...

Page 461: ...s TGET uploads trace information as well as trace data TPUT restores the trace type length and other attributes as well as the data The upload sequence is as follows Host Send TGET i Do NOT wait for IFC to be set in the Serial Poll status SR780 Returns n 4 byte binary long int which is the number of bytes needed to transfer the Trace buffer Host On receipt of n 4 byte binary long int executes a bi...

Page 462: ...e downloaded back to the SR780 at a later time using APUT The AGET and APUT commands allow a host computer to save and reload the Arbitrary buffer without using disks The upload sequence is as follows Host Send AGET i Do NOT wait for IFC to be set in the Serial Poll status SR780 Returns n 4 byte binary long int which is the number of bytes needed to transfer the Arbitrary buffer Host On receipt of...

Page 463: ...host computer This command is valid only via the GPIB interface The parameter i selects Ch1 0 or Ch2 1 The parameter j selects upload the whole buffer 0 or just the playback portion 1 The uploaded data should be saved in its entirety by the host computer The saved data can be downloaded back to the SR780 at a later time using CPUT The CGET and CPUT commands allow a host computer to save and reload...

Page 464: ...f an error is detected during transfer the Capture buffer reverts to the empty state and a command execution error occurs This may occur if there is insufficient Capture memory allocated Serial Poll until IFC bit 7 is set in the Serial Poll status before sending another command WGET The WGET command uploads the Waterfall buffer to the host computer This command is valid only via the GPIB interface...

Page 465: ... n bytes and the EOI If an error is detected during transfer the Waterfall buffer reverts to the empty state and a command execution error occurs This may occur if there is insufficient Waterfall memory allocated Serial Poll until IFC bit 7 is set in the Serial Poll status before sending another command Loading the Waterfall buffer loads data into the waterfall buffer and recalls the measurement p...

Page 466: ...s string is in the format Stanford_Research_Systems SR780 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 467: ...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 468: ...ection 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 name of the reference node ...

Page 469: ... 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 470: ...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 471: ...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 472: ...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 473: ...ir 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 or STB to read the Serial Poll status U...

Page 474: ...he 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 request when a TRIGGER occurs bit 0 in the Instrument Status enable register needs to be set INSE 1 command and bit 0 in the Serial Poll enable register must be set SRE 1 command W...

Page 475: ... 15 unused The Instrument status word reports on the overall measurement status of the instrument These status bits remain set until read by INST They are also cleared by the CLS command Use INSE to set bits in the Instrument status enable register Display Status Word Bit Name Set when 0 NEWA New data is available for DisplayA 1 AVGA DisplayA linear average has completed 2 STLA New settled data is...

Page 476: ...ll scale 3 HIV1 Input1 has exceeded 35 dBV Input range switched to 34 dBV 4 ARG1 Input1 has AutoRanged 5 7 unused 8 LOW2 Input2 has fallen below half full scale 9 HLF2 Input2 has exceeded half full scale 10 OVL2 Input2 has exceeded full scale 11 HIV2 Input2 has exceeded 35 dBV Input range switched to 34 dBV 12 ARG2 Input2 has AutoRanged 13 15 unused These status bits do not necessarily reflect the...

Page 477: ...h1 calibration memory fails 12 CAL2 Ch2 calibration memory fails 13 15 unused The Error status bits stay set until read by ERRS They are also cleared by the CLS command Use ERRE to set bits in the Error status enable register Bits 7 12 are set by the power on tests Bits 3 5 are set in the System Diagnostics ...

Page 478: ......

Page 479: ...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 SR780 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 480: ...ar recv 80 global GPIB receive string char cmd 80 global GPIB command string float rxBuff 401 array of IEEE floats 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 sr780 10 default GPIB address for SR780 subroutines at the end of this listing you may need to modify these for your interface card voi...

Page 481: ... mode atoi recv GetSr780 FAVT 0 type atoi recv GetSr780 FAVN 0 number atoi recv printf Avg mode d type d number d n n mode type number printf Avg start WaitAvg start a linear average and wait until done printf done n TxSr780 ASCL 0 ASCL 1 autoscale the displays 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 dis...

Page 482: ...ween 1 0 and 1 0 for i 0 i 2048 i txBuff i float i 2048 F This section needs to be modified for your GPIB interface printf Loading Arb buffer TxGpib sr780 ALOD 2048 use TxGpib so we don t wait for IFC SR780 will return a binary 1 to acknowledge transmit mla talk 10 status make SR780 a talker pc a listener rarray ack 4 length status binary read 4 bytes long int return value should be 1 printf d byt...

Page 483: ... a listener rarray ack 4 length status binary read 4 bytes long int return value should be 1 printf d bytes recvd val ld length ack TASC TLOD replaces the data in an existing Trace 5 The Trace measurement and length are not changed Download 34 bins of data real imaginary with commas to separate and EOI at the end First 33 bins are the spectrum last bin is the Total Power bin All points are complex...

Page 484: ...vice d status d n address status GetSpace void GetGpib int address routine to get an answer from a GPIB address modify this routine for your GPIB interface char temp 80 enter temp 80 length address status enter is the CEC routine to enter a string from an address Sets status 0 to indicate result OK 80 is maxlen actual received length is stored in length if status 0 handle receive errors here print...

Page 485: ...done int result avgdone avgdone 0 init avgdone status GetSr780 DSPS clear sticky bits in Display status word first TxSr780 STRT start lin average measurement do GetSr780 DSPS result atoi recv read display status word avgdone avgdone result 0x0202 Check for AVGA and AVGB status bits until both have occurred Remember they may not be set together in the same query Do not check for both in the same qu...

Page 486: ...0 Example Program SR780 Network Signal Analyzer char ch while kbhit getch clear the keyboard buffer printf n Space to continue Q to quit do ch char getch if ch q ch Q exit 0 exit while ch continue printf n ...

Page 487: ... 78W Files 6 4 Diskfiles and Remote Interface Files Using SRMERG EXE 6 4 Using the File Conversion Utility 6 5 Using SRTRANS to Convert Files to 78D to ASCII 6 5 Using SRTRANS to Convert Files to 78W to ASCII 6 6 Using SRTRANS to Convert Files to 78C to ASCII 6 6 Using SRTRANS to Convert Files to 78D to MAT file 6 7 Using SRTRANS to Convert Files to 78D to Universal File Format 6 7 Using SRBUF to ...

Page 488: ...al programs into the SR780 for display and comparison In order to meet both these needs the SR780 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 489: ... include a program SDFTOSR EXE to translate version 3 0 SDF files to SRS trace 78D files Note that because of specific differences between HP analyzers and the SR780 it is impossible to exactly match instrument setups on the two analyzers however measurement data is transferred exactly Matlab MAT Files MATLAB is a popular program for doing mathematics and for the analysis of numeric data Although ...

Page 490: ...iles Using SRMERG EXE Because buffers saved to the SR780 s internal disk drive with the Buffer to Disk softkey can span several disks and because it is necessary to record information regarding the total number of disks in the stored file buffers saved to disk with the Buffer to Disk softkey have a slightly different format from the corresponding buffers which are downloaded using the AGET I CGET ...

Page 491: ...SC will be created The default output file consists of a header section with instrument setup information followed by 4 columns of data The first column gives the data X axis values the second and third columns give the real and imaginary parts of the data and the 4th column gives the value of the selected view of the data N suppresses the output of the fourth data column view data A appends the A...

Page 492: ...play B W and Wb specify the range of traces for display A and display B that will be included in the output For instance Wa14 38 instructs the program to translate traces 14 through 38 of the display A waterfall buffer If this information is not given on the command line it will be prompted for by the program Using SRTRANS to Convert 78C to ASCII SRTRANS infile outfile A D inflie specifies the nam...

Page 493: ...ted Infile may contain wildcard characters if a set of 78D files is to be converted outfile may be either the name of a single file in which case all input files will be translated and appended to the single output file or may be the wildcard ext where each input file will be translated into an output file with the same name and the extension ext A specifies that output should be appended to an ex...

Page 494: ...FF Using SRBUF to Convert ASCII to 78C SRBUF infile outfile Bn Li Sn Xi YI infile specifies the ASCII file to be converted The file consists of a list of ASCII floating point numbers separated by whitespace characters If the file is to be uploaded to a capture buffer the floating point values correspond to a fraction of the full scale input voltage specified in the capture header If the file is to...

Page 495: ...infile outfile Vn infile specifies SDF file to be converted outfile specifies the name of the converted 78D file Vn specifies the version of your SR780 instrument You can find the version number of the instrument by pressing the system Show Version softkey on the SR780 For example use V109 for SR780 version 109 Note that since there is not a one to one correspondence between fields in the SDF file...

Page 496: ...delete all files on your drive however the USB drive must be formatted by the SR780 SR785 for the instrument to recognize the drive The USB drive installed in the SR780 SR785 has the capacity to create multiple drives There are two buttons on the far left of the drive The right button increments the drive number by one The left button increments the drive number by 10 You can use multiple drive nu...

Page 497: ...000 and it can retrieve data from drive 031 if the drive is set to 031 Only drive 000 can be read by a Windows 7 or Windows XP computer All other drives will be ignored The first drive should be 000 If you want to use the data on your computer or backup your settings to your computer the files must be in drive 000 no other drive will be seen ...

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