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Chapter 3

Operation

99

SR860 DSP Lock-in Amplifier

cables to connect the A output from the preamp to the A input of the SR860 and the B
output from the preamp (preamp ground) to the B input of the SR860. Use A

−

B as the

input configuration. Be sure to twist the A and B cables so that there is no differential
noise pickup between the cables.

The signal coupling and input impedance is now determined by the preamp.

The SR860 does NOT compensate for the gain of the preamp. The preamps will default
to their maximum gain. Measurements made by the SR860 with a preamp need to be
divided by the gain of the preamp.

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Summary of Contents for SR860

Page 1: ...Revision 2 01 Operation Manual SR860 500 kHz DSP Lock in Amplifier ...

Page 2: ...ent Service For warranty service or repair this product must be returned to a Stanford Research Systems authorized service facility Contact Stanford Research Systems or an authorized representative before returning this product for repair Information in this document is subject to change without notice Copyright Stanford Research Systems Inc 2016 All rights reserved Stanford Research Systems Inc 1...

Page 3: ...ne cord For 100V 120V use a 1 Amp fuse and for 220V 240V use a 1 2 Amp fuse See Appendix F page 177 for detailed fuse installation instructions Line Cord The SR860 has a detachable three wire power cord for connection to the power source and to a protective ground The exposed metal parts of the instrument are connected to the outlet ground to protect against electrical shock Always use an outlet w...

Page 4: ...t Warning Regarding Use With Photomultipliers and Other Detectors The front end amplifier of this instrument is easily damaged if a photomultiplier is used improperly with the amplifier When left completely unterminated a cable connected to a PMT can charge to several hundred volts in a relatively short time If this cable is connected to the inputs of the SR860 the stored charge may damage the fro...

Page 5: ...Safety and Preparation For Use iii SR860 DSP Lock in Amplifier ...

Page 6: ...iv Safety and Preparation For Use SR860 DSP Lock in Amplifier ...

Page 7: ...s 28 Scanning 30 Chapter 2 Lock in Amplifier Basics 37 What is a Lock in Amplifier 37 What Does a Lock in Measure 40 Block diagram 41 The Reference Oscillator 42 The Phase Sensitive Detectors 43 Time Constants and Sensitivity 44 Outputs and Scales 46 What is Dynamic Reserve Really 48 The Input Amplifier 50 Input Connections 51 Intrinsic Random Noise Sources 54 External Noise Sources 55 Noise Measu...

Page 8: ...nds 120 FFT Screen Commands 125 Scan Commands 128 Data Transfer Commands 132 Data Capture Commands 134 Data Streaming Commands 140 System Commands 143 Interface Commands 146 Status Reporting Commands 148 Status Byte Definitions 151 Appendix A Advanced Filters 155 Appendix B The FFT Display 161 Appendix C Using the Webserver 169 Appendix D Data Streaming and Capture 171 Appendix E Dual Reference De...

Page 9: ... whichever is greater Phase Setting Resolution 360 232 deg Phase Noise Ext TTL reference 0 001 rms at 1 kHz 100 ms 12 dB oct typical Internal reference 0 0001 rms at 1 kHz 100 ms 12 dB oct Phase Drift Sine Out to Signal In 200 mVrms 0 002 C below 20 kHz dc coupled input 0 02 C below 200 kHz 0 2 C below 500 kHz Harmonic Detect Detect at N fref where N 99 and N fref 500 kHz Dual F Reference Detect a...

Page 10: ...d by Aux In 4 Expand X Y and R may be expanded by 10 or 100 Capture Buffer 1 Mpoints internal data storage Store X X and Y R and θ or X Y R and θ at sample rates up to 1 25 MHz This is in addition to the data histories for the chart display Data Streaming Realtime streaming of data either X X and Y R and θ or X Y R and θ at sample rates up to 1 25 MHz over Ethernet interface Scanning One of the fo...

Page 11: ...Ethernet VXI 11 and telnet USB Flash Front panel slot for USB flash storage of screen shots and data and firmware upgrades Preamp Power 9 pin D connector to power SRS preamps Power 60 Watts 100 120 220 240 VAC 50 60 Hz Dimensions 17 W 5 25 H 17 D Weight 22 lbs Warranty One year parts and labor on materials and workmanship ...

Page 12: ...09 Set sine output dc mode RSRC INT EXT DUAL CHOP i 109 Set reference mode RTRG SIN POSttl NEGttl i 109 Set external reference trigger REFZ 50ohms 1Meg i 109 Set external reference input impedance PSTF j f HZ KHZ MHZ 110 Set frequency preset j to f PSTA j v NV UV MV V 110 Set sine amplitude preset j to v PSTL j v NV UV MV V 110 Set sine dc level preset j to v Signal Commands page description IVMD ...

Page 13: ...RF DAT1 DAT2 DAT3 DAT4 j OFF ON i 119 Turn data channel j strip graph off on GETSCREEN 119 Download screen capture image Strip Chart Commands page description GSPD i 120 Set horizontal scale from 0 5 s 0 to 2 days 16 GSCL DAT1 DAT2 DAT3 DAT4 j x 120 Set channel j vertical scale to x GOFF DAT1 DAT2 DAT3 DAT4 j x 120 Set channel j vertical offset GAUT DAT1 DAT2 DAT3 DAT4 j 121 Auto scale channel j G...

Page 14: ... the dc attenuator mode for scanning SCNINRVL i 129 Set the scan parameter update interval SCNENBL OFF ON i 129 Turn the scan off on SCNRUN 130 Start or resume the scan SCNPAUSE 130 Pause the scan SCNRST 130 Reset the scan SCNSTATE 130 Query the scan off reset run pause or done 0 4 SCNFREQ BEGin END j f HZ KHZ MHZ 130 Set the begin end frequency SCNAMP BEGin END j v NV UV MV V 130 Set the begin en...

Page 15: ... STREAMPORT i 142 Sets the Ethernet port to i 1024 65535 STREAMOPTION i 142 Sets big little endianness and integrity checking STREAM OFF ON i 142 Turn streaming off on System Commands page description TIME SEConds MINutes HOUrs j i 143 Set time DATE DAY MONth YEAr j i 143 Set date TBMODE AUTO INternal i 143 Set the 10 MHz timebase TBSTAT 143 Query the current 10 MHz timebase ext 0 or int 1 BLAZEX ...

Page 16: ...he standard event status byte SRE j i 148 Set the serial poll enable register STB j 148 Query the serial poll status byte PSC i 149 Set the Power On Status Clear bit ERRE j i 149 Set the error status enable register ERRS j 149 Query the error status byte LIAE j i 149 Set LIA status enable register LIAS j 150 Query the LIA status word CUROVLDSTAT 150 Query the present overload states ...

Page 17: ...E A command cannot execute correctly or a parameter is out of range 5 CMD An illegal command is received 6 URQ Set by any user front panel action 7 PON Set by power on LIA Status Word bit name usage 0 CH1OV CH1 output overload 1 CH2OV CH2 output overload 2 unused 3 UNLK External reference or Chop unlock detected 4 RANGE Input range overload detected 5 SYNCF Sync filter frequency out of range 6 SYN...

Page 18: ...yte bit name usage 0 CLK External 10 MHz clock input error 1 BACKUP Battery backup failed 2 unused 3 unused 4 VXI VXI 11 error 5 GPIB GPIB fast data transfer mode aborted 6 USBDEV USB device error interface error 7 USBHOST USB host error memory stick error ...

Page 19: ...attempting to perform an actual experiment Keys Knobs and Touch Buttons Key Front panel keys are referred to in square brackets Some keys have a second italicized label Press and hold these keys for 2 seconds to invoke the italicized function Knob Knobs are referred to in angle brackets Knobs are used to adjust parameters which have a wide range of values Some knobs have a push button function Som...

Page 20: ...indicated by the signal strength LEDs The sensitivity determines the scale factor for the analog outputs CH1 and CH2 as well as the numeric readouts and bar graphs The sensitivity does not affect the measurement values it simply determines how much signal corresponds to a full scale 10V output from CH1 and CH2 outputs and a 100 bar graph It also sets the scale for the 5 digit numeric displays The ...

Page 21: ... differential and common mode Use either sine out for single ended excitation Outputs The CH1 output can be proportional to either X or R while the CH2 output can be proportional to Y or θ Output functions include offset up to 999 of the sensitivity expand up to 100 and ratio These functions are generally only used when the CH1 or CH2 outputs are being used to drive other parts of an experiment ...

Page 22: ...ta displays as well as enter certain lock in parameters Screen Layout Press Screen Layout to cycle through the different screen layouts Trend Graph Full Screen Strip Chart Half Screen Strip Chart Full Screen FFT Half Screen FFT Big Numbers The SR860 displays up to 4 channels at a time in green blue yellow and orange Each channel is assigned a parameter using the Config key Parameters are chosen fr...

Page 23: ...ncy entry screen Numeric entry is straightforward Close will return to the data screen The buttons F1 F2 F3 and F4 are frequency presets Touching a preset will load the preset value immediately Touch and hold a preset button to memorize the current setting Other parameters may have slightly different entry screens Strip Charts The most common way to visualize the lock in outputs is to use the stri...

Page 24: ...at the right edge There is no zooming in about a point in the distant past All parameters which may be assigned to a data channel are continuously recorded even when they are not displayed This means that historical data can be viewed for all parameters simply by assigning them to a data channel and viewing the strip chart Strip charts may be paused When the graph is paused the cursor can be used ...

Page 25: ...dragging on the screen while the vertical scale palette is displayed Each graph can also be turned off Touch the scale tile to turn the graph back on All changes to the graphs are non destructive They simply change the way data is visualized Stored parameter values are not altered by scale changes Horizontal Scale Palette Horizontal scale changes are applied to the entire strip chart display and a...

Page 26: ...is paused Zooming in and out preserves the right hand edge of the graph at the point in time when the graph was paused Data storage continues in the background while the graph is paused When live scrolling is resumed with Resume the graph is redrawn so the current point is once again at the right edge ...

Page 27: ...erence frequency The default data screen is the Trend Graph The 4 displayed parameters default to X Y R and θ Each parameter has a numeric display a bar graph and a trend graph The trend graph is a continuously autoscaling graph of the recent history of each parameter This data screen has no adjustments available The default sine amplitude is 0 Vrms Thus the data displays will read 0 for X Y and R...

Page 28: ...hange the frequency to 10 kHz Use the Frequency knob to adjust the frequency to 1 00000 kHz The knob is very useful for making small adjustments or optimizing a setting Large changes are better left to the numeric keypad The measured signal amplitude X and R should stay within 1 of 500 mV and Y and θ should stay close to zero 7 Use the Amplitude knob to adjust the sine out to 5 0 mV The Amplitude ...

Page 29: ...e the signal at the A D converter without overload The Input Range should change to 100 mV 10 Press Input Range Down to select 30 mV Settings which have many options such as Input Range Time Constant and Sensitivity are changed with up and down keys The setting is indicated by LEDs The peak signal exceeds the input range so the Input Range Overload LED lights Ovld indicators also appear on the scr...

Page 30: ... an LED The outputs are less noisy with 2 poles of filtering Press Slope twice more to select 24 dB oct With 4 poles of low pass filtering even this short time constant attenuates the 2f component reasonably well and provides steady readings Press Slope again to select 6 dB oct Let s leave the filtering short and the outputs noisy for now 13 Press Sync to turn on synchronous filtering This turns o...

Page 31: ... sine wave from the synthesized function generator to the A input using a BNC cable and appropriate terminator The input impedance of the lock in is 10 MΩ The generator may require a terminator Many generators have either a 50Ω or 600Ω output impedance Use the appropriate feedthrough or T termination if necessary In general not using a terminator means that the function output amplitude will not a...

Page 32: ...dge and older data scrolls left The scroll rate is determined by the horizontal scale time per division The fastest rate is 0 5 s div and the shows 5 s of history The info bar is at the top of the screen Touch a tile to change a parameter using a keypad The numeric and bar graph displays shrink to fit above the chart The scale bar is shown below the strip chart This bar shows tiles indicating the ...

Page 33: ... scale tile Y to display its scale palette Touch to auto scale the blue Y trace The X and Y outputs are 0 2 Hz sine waves with 500 mV amplitudes 8 Touch the yellow scale tile R to display its scale palette Touch to move the trace so the newest points are vertically centered Touch repeatedly to zoom in about the center Keep zooming in until the yellow trace shows some noise The scale will probably ...

Page 34: ...ve an external monitor or TV Users who are looking at the monitor can see the lock in front panel settings Touch anywhere within the graph area to dismiss the status display The status display is dismissed when the graph area is touched or a scale palette is displayed Simply turn it back on with a touch if desired 11 Touch the white scale tile Time to display the horizontal scale palette Touch rep...

Page 35: ...ion goes away 13 Touch the white scale tile Time to display the horizontal scale palette Touch repeatedly to zoom out Touch repeatedly to zoom back in Zoom out on the horizontal time scale to show more and more history When the region where the signal was overloaded is shown the overload is indicated by the violet points along the bottom edge 14 Press Screen Layout once to change the display to th...

Page 36: ...he vertical and horizontal scales Avgs sets the amount of averages and Live toggles to Paused Use the Cursor knob to move the cursor 16 Press Screen Layout again to change the display to the half screen FFT The half screen FFT display behaves the same as the full screen version The only difference is that the numeric and bar graphs are full sized 17 Press Screen Layout again to change the display ...

Page 37: ... Amplifier 18 Press Screen Layout again to cycle back to the trend graph Use Screen Layout to cycle through the various display screens This concludes the measurement example You should have a feeling for the basic operation of the display screens ...

Page 38: ...put using a BNC cable The lock in defaults to the internal oscillator reference set at 100 000 kHz The default data screen is the Trend Graph The 4 displayed parameters default to X Y R and θ Each parameter has a numeric display a bar graph and a trend graph The trend graph is a continuously autoscaling graph of the recent history of each parameter This data screen has no adjustments available The...

Page 39: ...een Layout twice to show the half screen strip chart Now let s look at how the Sensitivity affects the different displays 6 Touch the green scale tile X to display its scale palette Touch to auto scale the green X trace Touch the green highlighted scale tile again to dismiss the scale palette auto scales the trace keeping zero at the center The zero location is indicated by the small green triangl...

Page 40: ...ar graphs Auto Scale will adjust the Sensitivity automatically 9 Press and hold the CH1 Offset knob above the CH1 BNC to display the offset keypad X Y and R may all be offset ratioed and expanded separately Since CH1 is set to X indicated by the X LED above the Select key the CH1 Offset knob and Expand key above the CH1 BNC set the X offset and expand The CH1 Select key determines which quantity X...

Page 41: ...center This is because the offset affects the value of X unlike the sensitivity 12 Press the CH1 Offset knob briefly once to turn the X offset off The offset for CH1 can be turned on and off without changing the offset value Notice how the trace of X changes when the offset is turned off Press it again to turn it back on Leave the X offset on for now 13 Press CH1 Expand once to select 10 Expand 10...

Page 42: ... V CH1 output The X graph is a line at 100 mV 2 divisions above center With offset and expand the output voltage gain and offset can be programmed to provide control of feedback signals with the proper bias and gain for a variety of situations Offsets add and subtract from the values of X Y and R Expand increases the resolution of the displays and analog outputs but does not change the values of X...

Page 43: ...rument parameters not measurement parameters are set This includes file numbering interface settings and software updates 3 Touch the h button in the Time section to highlight the hours setting Use the keypad to set the hour of day in 24 hour format The time date will highlight in orange indicating that the displayed time is not the current time but rather the time to be set Continue to enter the ...

Page 44: ...for this setup using the keypad Touch Confirm to commit the current setup to location 1 Setups are numbered 1 through 8 Setups should be named so they are easily distinguished 7 Now change the Sensitivity Time Constant and Filter Slope to new settings Change the lock in setup before recalling the saved settings 8 Press Save Recall to display the Save Recall screen again Note that the Location 1 ti...

Page 45: ...l for Location 1 A summary of settings which will change upon recall is shown Simply touch Cancel to skip recalling this setup Touch Confirm to recall the setup and dismiss this screen The Sensitivity Time Constant and Filter Slope should all return to the saved settings ...

Page 46: ...ocal pressed the lock in returns to its standard default settings See the Standard Settings list in the Operation section for a complete listing of the settings 2 Connect Aux Out 1 on the rear panel to the DVM Set the DVM to read dc volts The 4 Aux Outputs can provide programmable voltages between 10 5 and 10 5 volts The outputs can be set from the front panel or via the computer interface 3 Press...

Page 47: ...channels The Aux Inputs are always scaled to 10 V The Aux Inputs can read 4 analog voltages These inputs are useful for monitoring and measuring other parameters in an experiment such as pressure temperature position etc 6 Disconnect the DVM from Aux Out 1 Connect Aux Out 1 to Aux In 1 on the rear panel We ll use Aux Out 1 to provide an analog voltage to measure Aux In 1 should now read 5 000 V Th...

Page 48: ...edance of the lock in is 10 MΩ The generator may require a terminator Many generators have either a 50Ω or 600Ω output impedance Use the appropriate feedthrough or T termination if necessary In general not using a terminator means that the function output amplitude will not agree with the generator setting The internal oscillator should be very close to the actual generator frequency The X green a...

Page 49: ... at the top is shown in orange indicating that it is under scan control At this time the frequency is the start value or 99 9900 kHz 8 Press Play Pause reset briefly don t hold it to start the scan The Run LED turns on indicating that the scan is running The internal frequency starts scanning up The current value is shown in orange in the info bar When the end value is reached the scan resets to t...

Page 50: ...e R shows the lock in response as the internal frequency scans through the signal frequency at this time constant and filter Reduce the phase trace to see the resonance at 100 000 kHz 12 Press Config to change the assignments of the data channels Touch Data 2 Display the blue display to highlight the channel 2 data source Touch Fint from the keypad below Touch Close to return to the strip chart It...

Page 51: ...End Mode is set to repeat we see the scan repeat over and over in the history When scanning it is convenient to pause the strip chart at the end of the scan to review the results 15 Press and hold Scan setup to display the scan menu again Touch End Mode multiple times to select Once Touch Close to return to the strip chart When the End Mode is Once then the scan stops at the end value and the stri...

Page 52: ...he frequency will hold at the end value 100 010 kHz as displayed in the info bar The cursor is active when the strip chart is paused 20 Touch the white scale tile Time to display the horizontal scale palette bottom right of screen Touch start the strip chart again Touch the highlighted white scale tile again to dismiss the scale palette Notice that data collection continued while the chart was pau...

Page 53: ...0 DSP Lock in Amplifier While the scan is in progress press Scan setup briefly to turn scanning off Turn the scan off before the end and the internal frequency returns to its original value 100 000 kHz as shown in white in the info bar ...

Page 54: ...36 Getting Started Chapter 1 SR860 DSP Lock in Amplifier ...

Page 55: ...00 a very good filter centered at 10 kHz any signal in a 100 Hz bandwidth will be detected 10 kHz Q The noise in the filter pass band will be 50 μV 5 nV Hz 100 Hz 1000 and the signal will still be 10 μV The output noise is still much greater than the signal and an accurate measurement cannot be made Further gain will not help the signal to noise problem Now try following the amplifier with a phase...

Page 56: ...l be a dc signal In this case the filtered PSD output will be Vpsd 1 2 Vsig cos θsig θref This is a very nice signal it is a dc signal proportional to the signal amplitude Narrow band detection Now suppose the input is made up of signal plus noise The PSD and low pass filter only detect signals whose frequencies are very close to the lock in reference frequency Noise signals at frequencies far fro...

Page 57: ...nce source In many situations the lock in s internal oscillator may be used instead The internal oscillator is just like a function generator with variable sine output and a TTL sync which is always phase locked to the reference oscillator Magnitude and phase Remember that the PSD output is proportional to Vsigcosθ where θ θsig θref θ is the phase difference between the signal and the lock in refe...

Page 58: ...ignal proportional to the component of the signal whose frequency is exactly locked to the reference frequency The low pass filter which follows the multiplier provides the averaging which removes the products of the reference with components at all other frequencies The SR860 because it multiplies the signal with a pure sine wave measures the single Fourier sine component of the signal at the ref...

Page 59: ... cycles per second and math works best in radians For purposes of measurement frequencies as measured in a lock in amplifier are in Hz The equations used to explain the actual calculations are sometimes written using ω to simplify the expressions Phase is always reported in degrees Once again this is by custom Equations written as sin ωt θ are written as if θ is in radians mostly for simplicity Lo...

Page 60: ...t zero phase to the detected edge Internal Oscillator The internal oscillator in the SR860 is basically a 500 kHz function generator with sine and sync outputs The oscillator generates a digitally synthesized sine wave The internal oscillator sine wave is output differentially at the SINE OUT BNC s on the front panel An attenuator sets the amplitude of the output to a value between 1 nV and 2 V rm...

Page 61: ...the SR860 is very low and generally causes no problems In applications requiring no phase jitter the internal reference mode should be used Since there is no PLL the internal oscillator and the reference sine waves are directly linked and there is no jitter in the measured phase Actually the phase jitter is the phase noise of a crystal oscillator and is very very small Harmonic Detection It is pos...

Page 62: ...m the fact that the actual output is supposed to be a dc signal In fact when there is noise at the input there is noise on the output By increasing the time constant the output becomes more steady and easier to measure reliably The tradeoff comes when real changes in the input signal take many time constants to be reflected at the output This is because a single RC filter requires about 5 time con...

Page 63: ...tput BNC The Sensitivity also sets the scale for the displayed bar graphs and numerical readouts of X Y and R Note that this is a numerical output conversion Output overloads do not affect the actual measurement results They only indicate that the output value exceeds 100 of the chosen Sensitivity and the output BNC the bar graph and the displayed numerical readout will be pinned at their maximums...

Page 64: ...the rear panel and Channel 1 and 2 CH1 and CH2 outputs on the front panel X and Y Rear Panel Outputs The X and Y rear panel outputs are the outputs from the two phase sensitive detectors with low pass filtering offset and expand These outputs are the traditional outputs of an analog lock in The X and Y outputs update at 2 222 MHz CH1 and CH2 Front Panel Outputs The two front panel outputs can be c...

Page 65: ...hich is only 10 of sensitivity can be expanded to provide 10 V of output rather than only 1 V The normal use for expand is to expand the measurement resolution around some value which is not zero For example suppose a signal has a nominal value of 0 9 mV and we want to measure small deviations say 10 µV or so in the signal The Sensitivity of the lock in is set to 1 mV to accommodate the nominal si...

Page 66: ...nal value minus the offset Any display which is showing a quantity which is affected by a non unity expand will display a highlighted Expand indicator within its display Output expands affect the bar graphs The bar graphs are simply a visualization of the BNC outputs and as such are expanded to provide more visual resolution Output expands do not affect the strip charts The values being charted ar...

Page 67: ...ller value increases the analog gain The signal strength LEDs on the front panel indicate how much of the A D range is being used The general rule is to decrease the Input Range as much as possible without overloading the amplifier This increases the A D range used and optimizes the output noise performance of the lock in At an Input Range of 10 mV no additional gain is available since noise perfo...

Page 68: ...aussian noise the peak to peak noise is about 5 times the rms noise Thus the output will have about 20 nV pk pk of noise Remember that the SR860 reports its measurements in Volts referred to the input BNC In this case the SR860 will appear to have 20 nV pk pk of noise at fref at the input with its input grounded and no signal even applied If this noise floor is too large for your experiment then y...

Page 69: ...tions In order to achieve the best accuracy for a given measurement care must be taken to minimize the various noise sources that can be found in the laboratory With intrinsic noise Johnson noise 1 f noise or input noise the experiment or detector must be designed with these noise sources in mind These noise sources are present regardless of the input connections The effect of noise sources in the...

Page 70: ...s are susceptible to magnetic pickup Common Mode Signals Common mode signals are those signals which appear equally on both center and shield A or on the center of both A and B A B With either connection scheme it is important to minimize both the common mode noise and the common mode signal Notice that the signal source is held near ground potential in both illustrations above If the signal sourc...

Page 71: ...1 kΩ 10 nA range Currents from 3 µA down to 1 fA full scale can be measured The impedance of the signal source is the most important factor to consider in deciding between voltage and current measurements For high source impedances greater than 1 MΩ 1 μA range or 100 MΩ 10 nA range and small currents use the current input Its relatively low input impedance greatly reduces the amplitude and phase e...

Page 72: ...ise bandwidth of the measurement Since the input signal amplifier in the SR860 has a bandwidth of approximately 4 MHz the effective noise at the amplifier input is Vnoise 250 R nVrms or 1 3 R μV pk pk This noise is broadband and if the source impedance of the signal is large can determine the required Input Range of the lock in The amount of noise measured by the lock in is determined by the measu...

Page 73: ... noise in a current measurement The shot noise or current noise is given by f I 2 rms noise q I where q is the electron charge 1 6 10 19 coulomb I is the RMS ac current or dc current depending upon the circuit and f is the bandwidth When the current input of a lock in is used to measure an ac signal current the bandwidth is typically so small that shot noise is not important Total Noise All of the...

Page 74: ...60 Hz and Vnoise 120 V Cstray can be estimated using a parallel plate equivalent capacitor If the capacitance is roughly an area of 1 cm2 separated by 10 cm then Cstray is 0 009 pF The resulting noise current will be 400 pA at 60 Hz This small noise current can be thousands of times larger than the signal current If the noise source is at a higher frequency the coupled noise will be even greater I...

Page 75: ... Using magnetic shielding to prevent the magnetic field from crossing the area of the experiment 4 Measuring currents not voltages from high impedance detectors Resistive coupling or ground loops Currents flowing through the ground connections can give rise to noise voltages This is especially a problem with reference frequency ground currents In this illustration the detector is measuring the sig...

Page 76: ...ble This current affects the detector and the measured signal Some ways to minimize microphonic signals are 1 Eliminate mechanical vibrations near the experiment 2 Tie down cables carrying sensitive signals so they do not move 3 Use a low noise cable that is designed to reduce microphonic effects Thermocouple effects The emf created by junctions between dissimilar metals can give rise to many micr...

Page 77: ...f the average The averaging time is roughly 200 time constants for example if the time constant is 100 mS the noise measurement would take about 20 seconds to settle If the Sync filter is enabled that also affects the noise averaging time The averaging time due to the Sync filter is 100 Sync filter periods The final noise averaging time is the longer of these two averaging times or 0 5 seconds Sho...

Page 78: ... time is required If the time constant is changed then the noise measurement will need to settle to the new value X and Y noise are displayed in units of V rms The ENBW of the time constant is NOT factored into the calculation To convert to spectral noise density divide the reading by ENBW ...

Page 79: ... key with square brackets such as Key A complete description of the keys follows in this section Knobs Knobs are used to adjust the internal reference frequency reference phase shift sine output amplitude sine dc level offsets and Aux Output levels The knobs also have secondary key press functions labeled in italics below the knobs these functions are accessed by pressing the knob inward This manu...

Page 80: ...g edge The input impedance is either 1 MΩ or 50 Ω The Sine Trig is ac coupled 1 Hz For low frequencies 1 Hz it is necessary to use a TTL reference signal The TTL input provides the best overall performance and should be used whenever possible Sine Out The internal oscillator outputs are differential with 50 Ω output impedance each The output amplitude is specified as Vrms differential into 50 Ω lo...

Page 81: ...em menu Touch Sounds to toggle the key click on and off Display Off Operation Press the Blank key to operate with the front panel display and LEDs off The SR860 is still operating the outputs are active data collection continues and the unit responds to interface commands To change a setting press Blank to return to normal operation change the desired parameter then press Blank again Front Panel T...

Page 82: ...Reference Source Internal Internal Frequency 100 000 kHz Harmonic 1 Sine Amplitude 0 00 Vrms DC Level 0 0 V Ext Reference Trigger Sine Ext Reference Impedance 50 Ω Signal Input Voltage A B A Couple AC Ground Float Current Range 1 μA Input Range 1 V Time Constant 100 ms Filter Slope 6 dB Advanced Filter On Synchronous Off Sensitivity 1 V Outputs CH1 Output X CH2 Output Y All Offsets 0 00 All Expand...

Page 83: ...ground The largest allowable current before overload is around 3 µA 1 µA range or 30 nA 10 nA range No current larger than 10 mA should ever be applied to this input Voltage A B The voltage input can be either a single ended A or differential A B voltage The shields of A and B are connected and grounded by either 10 Ω Ground or 10 kΩ Float Voltage Couple This key selects the voltage input coupling...

Page 84: ...easing the gain In general use the smallest input range possible without overload Remember the largest signal whether it s at fref or just noise will be the first to overload This setting has no effect when the current input is selected The Signal Monitor on the rear panel is the amplifier output Current Range The current input uses the I connector The input burden resistance is 1 kΩ 10 nA range o...

Page 85: ...ppropriate units This time constant sets the bandwidth of the low pass filter after the phase sensitive detectors for X and Y This is the filter that removes signals at frequencies other than fref In general longer time constants provide more noise filtering and quieter measurements but longer response times The time constant also determines the equivalent noise bandwidth ENBW of the low pass filt...

Page 86: ...with RC filters They often yield better results in less time See Appendix A for more information about the advanced filters Filter Sync Pressing this key turns synchronous filtering on or off Synchronous filtering removes outputs at harmonics of the reference frequency most commonly 2 fref This is very effective at low reference frequencies since 2 fref outputs would require very long time constan...

Page 87: ... filter usually 1 fref Since the synchronous filter follows the phase sensitive detectors the time constant filters and output scaling any change in the signal amplitude reference frequency phase time constant slope or sensitivity will cause the outputs to settle for one period of the filter These transients are because the synchronous filter provides a steady output only if its input is repetitiv...

Page 88: ...le or range When CH2 outputs a voltage proportional to θ the output scale is 18 Volt or 180 10 V The phase bar graph and numeric readout scales are also unaffected by the Sensitivity Synchronous Filters and Noise Calculations Synchronous filtering and calculation of Xnoise and Ynoise are performed on the output scaled values of X and Y Thus their accuracy is affected by a poor choice of Sensitivit...

Page 89: ...Aux Input voltage of 1 000 V corresponds to unity Outputs which would exceed 10 V generate an Output Overload and the red output Overload LED will light Any corresponding displayed numeric value bar graph will indicate Scale in the display The actual measurement is unaffected since it is done in floating point and has no overload Data displayed in the strip chart will still be accurate The X and Y...

Page 90: ...l show an increased resolution but will continue to display the original value minus the offset Any display which is showing a quantity which is affected by a non unity expand will display a highlighted Expand indicator within its display Output expands affect the bar graphs The bar graphs are simply a reflection of the BNC outputs and as such are expanded to provide more visual resolution Output ...

Page 91: ...fsets can also be set using the keypad or by turning the Offset knob Turning the knob ALWAYS adjusts the offset even if the offset is toggled off and the keypad is not shown Offsets are set as a percentage of the Sensitivity up to 999 10 The offset percentage is not changed with the sensitivity it is an output function Touch Close to dismiss the keypad Touch Ratio to cycle between Off no ratio and...

Page 92: ...nfo bar across the top This bar always shows tiles displaying the reference phase frequency detected harmonic sine out amplitude and dc level Each of these parameters can be adjusted using the knobs and buttons in this section of the front panel Touching one of these tiles brings up a numeric keypad for direct entry ...

Page 93: ...to adjust the frequency In this mode the Sine Out is at the internal frequency External When the source is External the SR860 will phase lock to the external reference provided at the Ref In BNC The SR860 will lock to frequencies between 0 001 Hz and 500 kHz The external frequency is shown in the info bar The Frequency knob has no effect on the external frequency In this mode the Sine Out is at th...

Page 94: ... detection is at the measured external frequency The SR540 is driven to phase lock with this internal frequency but is subject to the mechanical limitations of its motor and slew rate The internal frequency is shown in the info bar Use the Frequency knob or the numeric keypad to adjust the internal frequency To record and view the external frequency use the Config key to assign fext to one of the ...

Page 95: ...cts the external reference input trigger mode TTL When either Pos TTL or Neg TTL is selected the SR860 locks to the selected edge of a TTL square wave or pulse train For reliable operation the TTL signal should exceed 1 5 V when high and be less than 0 5 V when low This trigger mode is dc coupled This input mode should be used whenever possible since it is less noise prone than the sine wave discr...

Page 96: ...o show the numeric entry screen When using an external reference the reference phase shift is the phase between the external reference and the digital sine wave which is multiplying the signal in the PSD This is also the phase between the sine output and the digital sine wave used by the PSD in either internal or external reference mode Changing this phase shift only shifts internal sine waves The...

Page 97: ...by the harmonic detection Its frequency is always the fundamental reference frequency Internal and Chop Reference When the reference mode is Internal or Chop these keys change the internal harmonic number Nint and detection is at Nint fint and the internal reference frequency is limited to 500 kHz Nint External Reference When the reference mode is External these keys change the external harmonic n...

Page 98: ...al can provide a trigger or sync signal to the experiment when the internal reference source is used This signal is also available when the reference is externally provided In this case the sync output is phase locked to the external reference DC Level This knob adjusts the sine out dc level The dc level is shown in the info bar at the top of the screen Touch the DC tile to show the numeric entry ...

Page 99: ...the different screen layouts Trend Graph Full Screen Strip Chart Half Screen Strip Chart Full Screen FFT Half Screen FFT Big Numbers Screen Shot Pressing Screen Shot saves a screen shot to the USB memory stick as a BMP file Set the Print Mode in the system menu Screen is an exact screen shot Print replaces the ...

Page 100: ...To change a setting press Blank to return to normal operation change the desired parameter then press Blank again The Blank LED is lit while the rest of the display is off Config The SR860 displays up to 4 channels at a time in green blue yellow and orange Each channel is assigned a parameter using the Config key Parameters are chosen from X Y R θ detected Fint Fext Reference Phase Sine Amplitude ...

Page 101: ...e data graph for wide cursors since the marker shows the min max or mean of all the data within the cursor width Relative Chart Cursor To read chart data relative to a reference point within the chart position the cursor at the desired reference location and press the Cursor knob once A stationary vertical line is placed at the reference location and the cursor readout values will be relative to t...

Page 102: ...r 3 SR860 DSP Lock in Amplifier Touch in the vertical scale paleete to change the width of the cursor In the FFT display the wide cursors always find the peak within the cursor region This makes reading an FFT much easier ...

Page 103: ...and that there is sufficient gain to drive the A D converter Remember that the signal input is both the signal at fref plus noise which may be much larger The largest component of the signal will determine the resulting input range When the input is at very low frequency Auto Range may not function well In this case it is better to watch the signal strength indicators and change the input range ma...

Page 104: ... the keypad Touch Confirm to commit the current setup or Cancel to quit the operation Locations which already contain a saved setup will show the setup name and the time and date it was saved Touch Recall for a location with a previously saved setup and a summary of settings which will change upon recall is shown Touch Cancel to skip recalling this setup or touch Confirm to recall the setup and di...

Page 105: ...stments may be made Local When a host computer places the unit in the REMOTE state the keys knobs and touchscreen are locked out The Remote indicator is on above the Local key To return to front panel operation press the Local key Press and hold Local while turning the power on to reset the unit to its default settings This does not affect the computer interface settings Save The SR860 can save da...

Page 106: ...time spent at each scan step along the way The shorter the time the more steps in the scan and the smoother the parameter varies The longer the time the fewer steps With experiments that take time to settle after a parameter change it is often beneficial to set the update time long enough to accommodate the settling The scan End Mode can be Repeat repeat Up Down or Once pause at the end When the E...

Page 107: ...ess and hold Play Pause reset to reset the scan back to the Begin Value This leaves the Ready LED on and turns the Done LED off Press Play Pause reset briefly to start the scan again To Stop Scanning Press Scan setup briefly don t hold it to turn off the scan This key turns scanning on and off The Play Pause reset has no effect unless scanning is on and the Ready LED is lit Turning the scan off re...

Page 108: ...perator follows all of its operands For more information ask your friends or check the internet The 2nd button switches the functions of the operator keys Note that the reference phase frequency and amplitude can be copied in and out of the calculator System Menu Press and hold Calc system to display the system menu The system menu is used to set non measurement parameters such computer interface ...

Page 109: ...s process for the date The time and date are used to label data files and screen shots as well as saved settings 10MHz Timebase The SR860 can accept an external 10 MHz timebase input on the rear panel This allows the internal reference frequency of the SR860 to remain frequency and phase stable with other SR860 units on the same timebase When set to Internal the external timebase input is ignored ...

Page 110: ...list of subdirectories Touch a subdirectory to select it as the destination Touch to go up one directory level Repeat until the desired directory is selected Prefix and Suffix File names are generated from the Prefix string and the Suffix number The Next File Name is shown The suffix number is automatically incremented after every file save The extension is BMP for screenshots and either CSV or MA...

Page 111: ...s to select a baud rate Select a terminator and parity VXI 11 and Web Settings The SR860 allows computers to connect via VXI 11 from a range of Trusted IP addresses or Disabled altogether Set the Trusted IP address using as a wildcard This allows any computer on a specified subnet VXI 11 access The SR860 has a webserver which allows computer access thru a webpage at the SR860 s IP address This acc...

Page 112: ... dropped packets Select the output Channels X X and Y R and θ or X Y R and θ and the desired Format 32 bit Float or 16 bit Integer Integers are scaled to the sensitivity The number of bits per sample point can range from 16 X integer to 128 XYRθ float This has an impact on the network bandwidth necessary to maintain the stream The Maximum Sample Rate can be set to Native depends on time constant o...

Page 113: ...ock in Amplifier The SR860 s firmware can be updated via the USB memory stick Follow the directions that accompany the update to prepare the memory stick Insert the memory stick into the front panel and press Update to start the process ...

Page 114: ...ystem key RS 232 Port The RS 232 interface port is configured as a DCE The baud rate and parity are set in the system menu hold the Calc system key The number of data bits is always 8 USB Port The USB port allows a computer to control the SR860 via USB The SR860 is a Test and Measurement Class instrument Ethernet Port The Ethernet port allows a computer to control the SR860 via an ethernet network...

Page 115: ... the resolution is 1 mV and the inputs are 1 MΩ These inputs can be displayed on the screen read over the computer interfaces and graphed on the strip charts Aux Out 1 4 These are auxiliary analog outputs The range is 10 5 V and the resolution is 1 mV These outputs may be programmed from the front panel via Aux Output scanned via Scan setup or controlled via the computer interfaces Aux Out 4 is us...

Page 116: ...e linked to the sine output zero crossings This is useful when the sine output amplitude is small and a synchronous trigger is required to a scope for example This output is active even when the SR860 is locked to an external reference BlazeX The BlazeX output is a 2V low latency version of the X output It s intended for experiments that require the fastest possible output response such as feedbac...

Page 117: ... Use A B as the input configuration Be sure to twist the A and B cables so that there is no differential noise pickup between the cables The signal coupling and input impedance is now determined by the preamp The SR860 does NOT compensate for the gain of the preamp The preamps will default to their maximum gain Measurements made by the SR860 with a preamp need to be divided by the gain of the prea...

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Page 119: ... RS 232 word length is always 8 bits The transmit terminator character s may also be specified Communicating With USB The SR860 is a Test and Measurement Class instrument and easily interfaces with LabVIEW NI VISA and Matlab Communicating With Ethernet The SR860 supports VXI 11 and telnet and interfaces easily with LabVIEW NI VISA and Matlab In addition SR860 has a built in webserver Data streamin...

Page 120: ...ter does not need to continually check the Interface Ready bit When using the GPIB interface serial polling may be used to check the Interface Ready bit in the Serial Poll Byte while an operation is in progress After the Interface Ready bit becomes set signaling the completion of the command then the ERR or ESB bit may be checked to verify successful completion of the command If an interface other...

Page 121: ... the command mnemonic and omitting the desired parameter s from the command No space is allowed between the command and the Values returned by the SR860 are sent as a string of ASCII characters If multiple queries are sent on one command line separated by semicolons of course the responses will be returned as semicolon separated strings Command Conventions Commands and arguments may be in either U...

Page 122: ...23456 KHZ Queries of f p or v always return the value in the base units of Hz degrees or Volts Enumerated Strings Many commands have an enumerated list of allowed settings It is possible to specify the setting with a string instead of the integer index Using the enumeration strings improves the readability of your source code Enumerated strings can either be the substring shown in CAPS or the full...

Page 123: ...60 DSP Lock in Amplifier Example Commands RSRC 1 Set reference source to external RSRC EXT RSRC Query the reference source FREQ 10E3 Set the internal reference frequency to 10000 Hz FREQ 10 KHZ FREQ 10000 0 APHS Execute Auto Phase ...

Page 124: ...may be specified in degrees default or millidegrees microdegrees radians milliradians or microradians Example PHAS 12 34 DEG Set the reference phase to 12 34 deg PHAS 1 234E1 PHAS 12340 MDEG PHAS Returns the reference phase in degrees APHS The APHS command performs the Auto Phase function This command is the same as pressing the Auto Phase key The outputs will take many time constants to reach the...

Page 125: ...rnal reference frequency Example FREQEXT Returns the external frequency in Hz FREQDET The FREQDET query returns the actual detection frequency This is helpful in dual reference mode or harmonic detection Otherwise the detection frequency is either the internal or external reference frequency Example FREQDET Returns the detection frequency in Hz HARM i The HARM i command will set the lock in to det...

Page 126: ...e effect since the SR860 will follow the chopper If multiple SR860 SR540 systems are being used in a single experiment BLADEPHASE can be used to modify the relative phase of the choppers Blade phase may be specified in degrees default or millidegrees microdegrees radians milliradians or microradians You can read more about chopper blade phase on page 77 Example BLADEPHASE 43 21 DEG Set the blade p...

Page 127: ...l i 1 dual i 2 or chop i 3 Example RSRC EXT Set the reference mode to external RSRC 1 RSRC Returns the reference mode i RTRG SIN POSttl NEGttl i The RTRG i command sets the external reference trigger mode to sine i 0 positive TTL i 1 or negative TTL i 2 Example RTRG POS Set the external reference trigger to positive TTL RTRG POSTTL RTRG 1 RTRG Returns the external reference trigger mode i REFZ 50o...

Page 128: ...s are available whenever the sine out amplitude keypad is displayed The parameter j 0 3 selects a preset A1 A4 The value of v will be rounded to 3 digits or 1 nV whichever is greater The value of v is limited to 1 nV v 2 0 V Example PSTA 2 12 3 MV Set amplitude preset A3 to 12 3 mV PSTA 2 0 0123 PSTA 2 Returns the amplitude preset A3 in Volts PSTL j v NV UV MV V The PSTL j v command sets a sine ou...

Page 129: ...e ICPL i command sets the voltage input coupling to ac i 0 or dc i 1 Example ICPL DC Set the voltage input coupling to dc ICPL 1 ICPL Returns the voltage input coupling mode i IGND FLOat GROund i The IGND i command sets the voltage input shields to float i 0 or ground i 1 Example IGND FLO Set the voltage input shields to float IGND FLOAT IGND 0 IGND Returns the voltage input grounding mode i IRNG ...

Page 130: ...ample ILVL Returns the signal strength indication SCAL i The SCAL i command sets the sensitivity according to the table below i sensitivity i sensitivity 0 1 V μA 15 10 μV pA 1 500 mV nA 16 5 μV pA 2 200 mV nA 17 2 μV pA 3 100 mV nA 18 1 μV pA 4 50 mV nA 19 500 nV fA 5 20 mV nA 20 200 nV fA 6 10 mV nA 21 100 nV fA 7 5 mV nA 22 50 nV fA 8 2 mV nA 23 20 nV fA 9 1 mV nA 24 10 nV fA 10 500 μV pA 25 5 ...

Page 131: ... oct i 1 18 dB oct i 2 or 24 dB oct i 3 Example OFSL 1 Set the filter slope to 12 dB oct OFSL Returns the filter slope i SYNC OFF ON i The SYNC i command turns the synchronous filter off i 0 or on i 1 Example SYNC ON Set the synchronous filter to on SYNC 1 SYNC Returns the state of the synchronous filter i ADVFILT OFF ON i The ADVFILT i command turns the advanced filter off i 0 or on i 1 Example A...

Page 132: ...CEXP 1 2 CEXP 1 Returns the Y expand mode i CEXP Y COFA X Y R j OFF ON i The COFA j i command turns the output offset for X j 0 Y j 1 or R j 2 to off i 0 or on i 1 Setting an offset for phase is not allowed Example COFA X ON Set X output offset to on COFA 0 1 COFA 0 Returns the X output offset state i COFA X COFP X Y R j x The COFP j x command sets the output offset percentage for X j 0 Y j 1 or R...

Page 133: ...r phase is not allowed The ratio function for X and Y are tied to aux input voltage 3 following the equation V 10 Expand V 1 000 3 In Aux Offset y Sensitivit orY X Output The ratio function for R is similar but is tied to aux input voltage 4 V 10 Expand V 1 000 4 In Aux Offset y Sensitivit R Output Example CRAT X ON Set X ratio mode to on CRAT 0 1 CRAT 0 Returns the X ratio mode CRAT X ...

Page 134: ...l Example OAUX 0 Returns the aux in1 voltage v OAUX 1 Returns the aux in2 voltage v AUXV j v NV UV MV V The AUXV j v command sets an aux output to voltage v The parameter j 0 3 selects aux output 1 4 on the rear panel The voltage v can be set from 10 5 V to 10 5 V Example AUXV 2 678 9 MV Set aux out3 to 678 9 mV AUXV 2 6 789E 1 AUXV 2 0 6789 AUXV 2 Returns the aux out3 voltage setting in Volts ...

Page 135: ...priate amount of time ARNG The ARNG command performs the Auto Range function This command is the same as pressing the Auto Range key The outputs may take many time constants to return to their steady state values ASCL The ASCL command performs the Auto Scale function This command is the same as pressing the Auto Scale key This automatically sets the sensitivity Measurements with the synchronous fi...

Page 136: ... USB memory stick must be present in the front panel USB port CDSP DAT1 DAT2 DAT3 DAT4 j parameter i The CDSP j param command assigns a parameter to data channel j This is the same parameter assignment as pressing the Config key The value of j 0 3 corresponds to the DAT1 green DAT2 blue DAT3 yellow and DAT4 orange data channels The parameter list is i enumeration parameter i enumeration parameter ...

Page 137: ...is written to a USB memory stick upon pressing the Screen Shot key After sending GETSCREEN the user s remote program should repeatedly perform a Status Byte query either by serial poll or through the VISA Read STB function but not with the STB query until the MAV bit becomes set Note that it may take several seconds before MAV is set Once the MAV bit is set in the Status Byte the user may then rea...

Page 138: ... j to x div The scale will be set to the nearest allowed scale in a 1 2 5 sequence The value of j 0 3 corresponds to the DAT1 green DAT2 blue DAT3 yellow and DAT4 orange data channels Example GSCL DAT2 0 1 Set the vertical scale for data channel 2 blue to 0 1 div GSCL 1 0 09 GSCL 1 0 12 GSCL 1 Returns the vertical scale for data channel 2 blue GSCL DAT2 GOFF DAT1 DAT2 DAT3 DAT4 j x The GOFF j x co...

Page 139: ... yellow and DAT4 orange data channels Example GACT DAT1 Auto Scale zero center data channel 1 green GACT 0 GAUF DAT1 DAT2 DAT3 DAT4 j The GAUF j command performs an Auto Find on data channel j This command is the same as pressing the button in the scale palette The value of j 0 3 corresponds to the DAT1 green DAT2 blue DAT3 yellow and DAT4 orange data channels Example GAUF DAT4 Auto Find data chan...

Page 140: ...If the chart is live then the marker is set to the most current bin location corresponding to the right and edge of the chart the marker however will not become visible until the chart is paused Example CURREL ON Set cursor to relative mode CURREL 1 CURREL Returns the cursor relative mode state i CURDISP i The CURDISP i command sets the cursor horizontal position display mode to date and time i 0 ...

Page 141: ...T j 4 returns 0 if there is no overload or unlock at the cursor positon The cursor is only available when the strip chart is paused The status response encodes three distinct sources that cause the violet error mark to appear at the bottom of the strip chart display Bit Weight Definition 0 1 Timebase error 1 2 External reference unlock 2 4 Signal overload 3 8 Sync filter error Example SCRY DAT2 Re...

Page 142: ... 00 In this example the cursor position is 2 days 16 hours 7 minutes and 30 seconds before the chart was paused corresponding to PCUR 171 on the 1 day division GSPD 15 chart When the cursor is in relative mode CURINTERVAL returns the interval between the cursor position and the marker position Performing the CURINTERVAL query when the display is not paused generates a parameter range error ...

Page 143: ...i 1 or post time constant filter i 2 Example FFTR FILT Set the FFT source to post time constant filter FFTR 2 FFTR Returns the FFT source i FFTS i The FFTS i command sets the FFT vertical scale dB div according to the table below i dB div i dB div 8 2 m 0 1 0 7 5m 1 2 0 6 10 m 2 5 0 5 20 m 3 10 4 50 m 4 20 3 100 m 5 50 2 200 m 6 100 1 500 m 7 200 The argument i is limited to 20 i 20 Vertical scale...

Page 144: ...d span as returned by FFTMAXSPAN The FFT span will be set to the nearest allowed span max span divided by powers of 2 Example FFTSPAN 305 Set the FFT span to 305 2 Hz div FFTSPAN Returns the FFT span in Hz div FFTA AVG1 AVG3 AVG10 AVG30 AVG100 i The FFTA i command sets the FFT averaging to 1 i 0 3 i 1 10 i 2 30 i 3 or 100 i 4 Example FFTA AVG3 Set the FFT averaging to 3 FFTA 1 FFTA Returns the FFT...

Page 145: ... in Hz FCRX is a query only command Example FCRX Returns the FFT cursor frequency value FCRY The FCRY query returns the amplitude value of the FFT cursor readout in dB FCRY is a query only command Note that FCRY only returns valid data when the SR860 display is set to FFT mode Example FCRY Returns the FFT cursor amplitude value ...

Page 146: ... the scan end mode to repeat SCNLOG 1 SCNLOG Returns the scan end mode i SCNSEC x The SCNSEC x command sets the scan time to x seconds The scan time is limited to 20 days 1728000 seconds Example SCNSEC 1234 Set the scan time to 1234 seconds 20 34 SCNSEC 1 234E3 SCNSEC Returns the scan time in seconds SCNAMPATTN i The SCNAMPATTN i command sets the operating mode for the output attenuators when scan...

Page 147: ... transients in the sine output Example SCNDCATTN 1 Set the scan dc level attenuator mode to fixed SCNDCATTN Returns the mode for dc level output attenuators SCNINRVL i The SCNINRVL i command sets the parameter update interval according to the table below i Update Interval i Update interval 0 8 ms 9 9 375 s 1 16 ms 10 28 12 s 2 31 ms 11 56 25 s 3 78 ms 12 112 5 s 4 155 ms 13 5 m 37 s 5 469 ms 14 11...

Page 148: ...end j 1 frequency to f The value of f will be rounded to 6 digits or 0 1 mHz whichever is greater The value of f is limited to 1 mHz f 500 kHz Example SCNFREQ BEG 1234 Set the begin frequency to 1 234 kHz SCNFREQ 0 1 234 KHZ SCNFREQ 0 Returns the begin frequency SCNAMP BEGin END j v NV UV MV V The SCNAMP j v command sets the begin j 0 or end j 1 ref amplitude to v The value of v will be rounded to...

Page 149: ...10 5 V with 1 mV resolution Example SCNAUX1 BEG 4 567 Set the begin AuxOut1 value to 4 567 V SCNAUX1 0 4567 MV SCNAUX1 0 Returns the begin AuxOut1 value SCNAUX2 BEGin END j v NV UV MV V The SCNAUX2 j v command sets the begin j 0 or end j 1 AuxOut2 value to v The voltage v can be set from 10 5 V to 10 5 V with 1 mV resolution Example SCNAUX2 END 4 567 Set the end AuxOut2 value to 4 567 V SCNAUX2 1 ...

Page 150: ...output 12 PHAse Reference Phase 4 IN1 Aux In1 13 SAMp Sine Out Amplitude 5 IN2 Aux In2 14 LEVel DC Level 6 IN3 Aux In3 15 FINT Int Ref Frequency 7 IN4 Aux In4 16 FEXT Ext Ref Frequency 8 OUT1 Aux Out1 Example OUTP 1 Returns the value of Y OUTP Y SNAP j k l The SNAP query returns the values of 2 or 3 parameters at a single instant For example SNAP is a way to query values of X and Y or R and θ whic...

Page 151: ...ere requested In this example the returned string might be 0 951359 0 0253297 1 234 The first value is X the second is Y and the third is Aux In1 Not all parameters are measured at the same rate within the SR860 The external frequency for example is only measured every reference period at low frequencies The most recent measurements for these parameters are returned by SNAP ...

Page 152: ...ivided by factors of 2 Note that if the time constant is modified during a capture the sampling rate will change mid capture This will likely create confusing results and should be avoided For the case of one sample per trigger capture see below data is stored when a trigger is detected The hardware trigger rate shouldnever exceed the maximum capture rate otherwise the SR860 will capture fewer sam...

Page 153: ...ger In both cases a falling edge at the BNC input triggers the start or stop of capture The TRIG IN BNC has a 10 kΩ internal pull up resistor to 3 3 V giving users flexibility around interfacing In one sample per trigger mode mode a new sample is captured every falling edge of the external trigger The data capture rate is determined by the rate of external triggers and need not be periodic The ext...

Page 154: ...or a given buffer length total data points capturing more parameters results in fewer points of each parameter and a shorter total capture time The capture rate is unaffected by CAPTURECFG Example CAPTURECFG 1 Capture X and Y CAPTURECFG XY CAPTURECFG Returns the capture configuration i CAPTURERATEMAX The CAPTURERATEMAX query returns the maximum allowed capture rate at the current time constant in ...

Page 155: ... edge For hardware triggered start or stop a triggered start requires using OneShot acquisition while a triggered stop required using Continuous acquisition Both parameters i and j are required in this command This command clears any previously captured data and starts a new capture Example CAPTURESTART ONE IMM Starts OneShot capture immediately CAPTURESTART 0 0 CAPTURESTOP The CAPTURESTOP command...

Page 156: ...at are overwriting old data the number of captured bytes decreases by 2048 bytes before increasing again After capture has stopped this query returns the actual number of bytes of non zero data For example an 8kB buffer is being filled with data being captured every trigger After capturing 1250 samples of X 5000 bytes of capture capture is stopped CAPTUREBYTES will report 5000 bytes of data while ...

Page 157: ...eturns wrapped data The maximum length j is 64 corresponding to 64 kbytes Both parameters i and j must be provided Capture must be stopped when executing CAPTUREGET or a range error is generated The binary block query response is in the following format nccccxxxxxxx Where is the hash character character code 35 n is a single digit specifying the number of digits to follow in the block length count...

Page 158: ...low faster streaming rates up to a limit of 1 25 MHz The actual streaming rate can be set to the maximum allowed rate divided by factors of 2 Starting and Stopping The STREAM ON OFF command turns streaming on and off NOTE Changes to streaming parameters only take effect when streaming is turned back on So if you want to change e g the kind data being streamed you need to turn streaming off change ...

Page 159: ...e streaming rate to the maximum rate divided by 2n The value of n is limited to 0 n 20 Set n 0 for the maximum streaming rate For example if STREAMRATEMAX returns 78125 then STREAMRATE 4 will set the streaming rate to 78125 24 4882 8125 Hz The STREAMRATE query returns the value n Example STREAMRATE 4 Sets the streaming rate to the max rate divided by 2 4 STREAMRATE Returns the streaming rate n STR...

Page 160: ...ta in little endian format while setting bit 0 false sends data in big endian format Setting bit 1 true enables data integrity checking while setting bit 1 false disables data integrity checking By default data is sent in big endian format with integrity checking i 2 Bit Weight Definition 0 1 Use little endian 1 2 Use data integrity checking Example STREAMOPTION 1 Send data in little endian format...

Page 161: ...20 21 DATE 2 21 DATE YEAR Returns the system clock year last 2 digits TBMODE AUTO INternal i The TBMODE i command sets the external 10 MHz timebase mode to auto i 0 or internal i 1 Example TBMODE AUTO Set the timebase mode to auto TBMODE 0 TBMODE Returns the timebase mode i TBSTAT The TBSTAT query returns the current 10 MHz timebase source either external 0 or internal 1 Example TBSTAT Returns the...

Page 162: ... Example SDFM CSV Set the data file format to csv SDFM 0 SDFM Returns the data file format i FBAS s The FBAS s command sets the file name prefix to the string s The string s must be within quotes All letters will be converted to upper case The string s is limited to 7 characters and may only contain characters which are allowed in DOS file names Example FBAS F65 Set the file name prefix to F65 FBA...

Page 163: ...CAP The DCAP command is the same as pressing the Screen Shot key The file save will take some time to complete A USB memory stick must already be in the front panel USB port SVDT The SVDT command is the same as pressing the Data Save key The file save will take some time to complete A USB memory stick must already be in the front panel USB port ...

Page 164: ...rd Event Status register see page 152 Querying OPC Always returns a 1 but does not affect the Standard Event Status register LOCL i The LOCL command sets the local remote function If i 0 the SR860 is set to LOCAL if i 1 the SR860 will go REMOTE and if i 2 the SR860 will go into LOCAL LOCKOUT The states duplicate the GPIB local remote states In the LOCAL state both command execution and keyboard in...

Page 165: ...de Remote is On then the front panel is NOT locked out when the unit is in the REMOTE state The REMOTE indicator will still be on and the LOCAL key will still return the unit to the Local state The default mode is Overide Remote On To lock out the front panel use the OVRM 0 command before local lock out Example OVRM 0 Set Overide Remote to No OVRM Returns the Overide Remote state i ...

Page 166: ...ber from 0 to 255 The ESR j command queries the value 0 or 1 of bit j 0 7 Reading the entire byte will clear it while reading bit j will clear just bit j Example ESR Returns decimal value of the standard event status byte ESR 4 Returns bit 4 of the standard event status byte SRE j i The SRE i command sets the serial poll enable register to the decimal value i 0 255 The SRE j i command sets bit j 0...

Page 167: ...ample ERRE 48 Set bits 4 and 5 in the error status enable register ERRE 4 1 Set bit 4 in the error status enable register ERRE Returns decimal value of the error status enable register ERRE 4 Returns bit 4 of the error status enable register ERRS j The ERRS command queries the value of the error status byte The value is returned as a decimal number from 0 to 255 The ERRS j command queries the valu...

Page 168: ...CUROVLDSTAT The CUROVLDSTAT command queries the present overload states of the lock in These overloads reflect the state of the lock in at the time the command is processed They are NOT set until read The value is returned is a decimal number from 0 to 4095 where the bits are defined below Bit Weight Definition 0 1 CH1 output scale 1 2 CH2 output scale 2 4 unused 3 8 External reference unlocked 4 ...

Page 169: ...OT cleared by reading the status byte using STB The bit stays set as long as the status condition exists This is true even for SRQ SRQ will be set whenever the same bit in the serial poll status byte AND enable register is set This is independent of whether a serial poll has occurred to clear the service request Using GPIB Serial Poll Except for SRQ a bit in the Serial Poll status byte is NOT clea...

Page 170: ...s set Since bit 3 in the LIA Status byte AND Enable register is set this ALSO sets bit 3 LIA in the Serial Poll Status byte Since bit 3 in the Serial Poll Status byte AND Enable register is set an SRQ is generated Bit 6 SRQ in the Serial Poll Status byte is set Further reference unlocks will not generate another SRQ until the UNLK status bit is cleared The UNLK status bit is cleared by reading the...

Page 171: ...nnel 2 scale overload 10 DAT3OV Data Channel 3 scale overload 11 DAT4OV Data Channel 4 scale overload 12 DCAPFIN Display capture to USB stick completed 13 SCNST Scan started 14 SCNFIN Scan completed The LIA Status bits stay set until cleared by reading or by the CLS command Error Status Byte bit name usage 0 CLK External 10 MHz clock input error 1 BACKUP Battery backup failed 2 unused 3 unused 4 V...

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Page 173: ...evertheless there are filters other than simple RC filters which offer quantifiable benefits to lock in users What are these benefits For two filters with the same noise bandwidth i e whose outputs would be equally noisy if the input was white noise a lock in user would always prefer a filter with a faster transient response and minimal overshoot And a lock in user would always prefer a filter wit...

Page 174: ...simply adding identical poles in succession Because the Gaussian filter is computationally intensive it is not available for time constants longer than 3s Linear Phase Filter For time constants of 10 s through 30000 s the advanced filter is a Linear Phase IIR filter with same attenuation slope as the RC filters of the same time constant and number of poles In other words the Linear Phase filter s ...

Page 175: ...f the different filters also see Step Response graphs on the following pages The chart below summarizes the noise bandwidth of the different filters Note that for a single stage all 3 filters are designed with the same noise bandwidth Equivalent Noise Bandwidth fraction of fc 2π time constant 1 Stages RC Gaussian Linear Phase 1 1 6 1 6 1 6 2 0 79 1 1 0 93 3 0 59 0 94 0 83 4 0 5 0 81 0 78 Time to s...

Page 176: ...Graphs These graphs illustrate the frequency response of the different filters at 12 and 24 dB oct Each stage of the Gaussian filter has the same ENBW as a single stage of the RC filter Each stage of the Linear Phase filter has the same roll off as a single stage of the RC filter ...

Page 177: ...Response Graphs These graphs illustrate the step response of the different filters at 12 and 24 dB oct The advanced filters always settle in less time than the RC filters Gaussian filters have increasing latency with more stages Linear Phase filters have 1 overshoot ...

Page 178: ...when using the BlazeX output In this example the input signal is a 500 kHz sinewave that abruptly changes from 10 mVrms to 20 mVrms The output filter is configured as RC 18 dB oct with a 1µs time constant Notice the BlazeX output begins responding to the amplitude step change after only 1 7 µs while the regular X output does not begin to respond until after 10 µs ...

Page 179: ...king separate measurements at fref 2 fref 3 fref etc the FFT can display the harmonic frequencies and amplitudes with amazing clarity in a single measurement Another example is noise analysis In an FFT the noise as a function of frequency is displayed The FFT Analyzer The lock in amplifier digitizes the input signal and multiplies by fref in a phase sensitive detector yielding a very narrow band m...

Page 180: ...eplacement for a full FFT spectrum analyzer instrument It is intended to give the user an overview of the spectrum of the input signal or the output of the PSD and time constant filters The length of the time record is always 1024 points the maximum span of an output FFT is determined by the time constant the window is Kaiser and the averaging is rms The amplitude is always dB Vrms and is uncalibr...

Page 181: ...A input using a BNC cable and appropriate terminator The input impedance of the lock in is 10 MΩ The generator may require a terminator Many generators have either a 50Ω or 600Ω output impedance Use the appropriate feedthrough or T termination if necessary In general not using a terminator means that the function output amplitude will not agree with the generator setting The SR860 is set to an int...

Page 182: ...rsor In the FFT display the wide cursors always find the peak within the cursor region This makes reading an FFT much easier Touch the highlighted dB div tile again to dismiss the scale palette Notice that the cursor readout at the upper right reads the peak amplitude and frequency This is the signal from the external generator The peak is about 20 dB or 0 1 Vrms The cursor reads 97 6562 kHz This ...

Page 183: ...s to 10 FFT graphs can be averaged to reduce fluctuations Averaging is exponential in the number of averages Touch twice to decrease the number of averages to 1 Turn the averaging off to speed up the display 5 Touch the Live tile along the bottom to pause the FFT display Touch Paused to return to a live display The FFT may be paused Press the Time Constant Down key multiple times to set the time c...

Page 184: ...pan is about 1 kHz At a 1 ms time constant the maximum span is about 50 kHz 4 883 kHz div At a 1 s time constant the maximum span is 1 6 kHz 152 6 Hz div 8 Increase the external generator frequency to 101 000 kHz Move the cursor to the peak Decrease the external generator frequency to 99 000 kHz The signal peak moves to the right of center and the cursor reads 101 00 kHz The signal peak moves to t...

Page 185: ...ease the filter slope to 12 dB oct The peak amplitude at 99 000 kHz is diminished even further This is the effect of the steeper time constant filter At the lock in output the 1 kHz output is attenuated further by this filter This example has provided a quick overview of the FFT display in the SR860 ...

Page 186: ...168 The FFT Display Appendix B SR860 DSP Lock in Amplifier ...

Page 187: ...e unit s IP address into the browser bar of a computer which can access the same subnet Note that typical installations do not allow the unit to be seen on the internet only on the internal subnet For full internet access consult with your IT administrator The homepage is shown below Various instrument properties are displayed This is an easy way to check the ethernet settings without writing any ...

Page 188: ...170 Using the Webserver Appendix C SR860 DSP Lock in Amplifier Click the Monitor Output tab to display a simple readout of the 4 data channels ...

Page 189: ...most significant byte of the word and B0 is the least significant byte Little endian format reverses the byte order so that the same 32 bit 4 byte word is stored as B0 B1 B2 B3 Similarly a 16 bit 2 byte integer is stored as B1 B0 in big endian format while it is B0 B1 in little endian format If the streamed data is not in the same endianness as the receiving computer then the byte order of the dat...

Page 190: ...n 0 and 31 inclusive This sample rate already takes into account the subsampling requested in the command STREAMRATE Status bit 24 is high when an input overload sync filter overload if sync filter is on or output overload if integer data is contained in the packet condition existed at the beginning of the packet Bit 25 is high when a PLL unlock or sync filter out of range condition existed at the...

Page 191: ...te is 1 25MHz If floating point XYRθ data is streamed then the data rate can exceed 1 25 MHz 4 channels 4 bytes 20 MBytes s This data rate requires Gigabit ethernet to work Fast 100Mb s ethernet is not sufficient to support the maximum data rate At high data rates we recommend putting the SR860 and the receiving computer on the same dedicated network This reduces traffic congestion for other users...

Page 192: ......

Page 193: ...modulation of the signal This results from the mixing of 2 frequencies in the experiment Often one of the frequencies is much lower than the other Let s call these frequencies ωcar and ωmod for carrier and modulation and assume ωmod ωcar If the carrier signal is sin car car t A ω then the experiment modulates this by multiplying by the modulation signal resulting in cos cos 2 sin sin mod car mod c...

Page 194: ...two frequencies and will always be lower than the greater frequency The original experimental signal contains components at the sum and difference frequencies cos cos 2 mod car mod car mod car t t A A ω ω ω ω In Dual Reference mode the SR860 multiplies by cos ωcar ωmod t in a single step resulting in the output 2 cos 2 cos 2 cos 1 4 mod car mod car mod car t t t A A ω ω ω ω The SR860 time constant...

Page 195: ...ates both North American single fuse or metric dual fuse operation This appendix provides detailed instructions for modifying the input voltage selection and replacing the line fuse Power Entry Module The line cord receptacle power switch fuse holder and line voltage selector are all part of the power entry module located on the rear panel of the SR860 Detailed instructions for changing the line v...

Page 196: ... for detailed illustrations 3 Pull the voltage selector card straight out of the housing using small needle nose plyers to grip the plastic indicator pin body 4 Orient the selector card so that the desired line voltage is readable at the bottom 5 Orient indicator pin to point up when desired line voltage is readable at the bottom note that when indicator pin is fixed successive voltages are select...

Page 197: ...ow to install or replace the fuse s 1 Disconnect and remove the power cord 2 Insert a small screwdriver at the point X as shown 3 Gently lift the entire door back away from the rear panel of the SR860 Lift away approximately 0 25 6 mm Once lifted the door will pivot on its hinges to expose the fuse holder 4 When the fuse holder is installed in the single fuse North American position apply a screwd...

Page 198: ...ether at the same time Also note that when installing the North American AG fuse the fuse is not centered on the plastic retaining hook but rather shifted towards the right hand side see image above left If the fuse is not propertly aligned the fuse holder will not seat properly and line voltage will not be provided to the instrument 6 Replace fuse holder into housing fuse first Be sure to align t...

Page 199: ...nown default state To do this press Save Recall then touch Recall default Touch Confirm to reset the SR860 to its default settings Each test generally starts with a preset This procedure will be referred to as PRESET Front Panel Test To test the front panel press and hold Local and then Auto Range at the same time Turn any knob to run through all of the LEDs Make sure all of the knobs and all of t...

Page 200: ...s are performed It is necessary to turn the unit off and on to preset it As long as the unit is powered on immediately this will not affect the test results Necessary Equipment The following equipment is necessary to complete the performance tests The suggested equipment or its equivalent should be used 1 Frequency Synthesizer Freq Range 1 Hz to 500 kHz Freq Accuracy better than 5 ppm Harmonic Dis...

Page 201: ... its operation using a DVM scope or some other piece of test equipment After checking the setup repeat the test from the beginning to make sure that the test was performed correctly If the test continues to fail contact Stanford Research Systems for further instructions Make sure that you have the unit s serial number and firmware revision code handy Have the test record on hand as well ...

Page 202: ...ollowing adjustments Touch Fint to display the internal frequency keypad Enter a frequency of 1 00 Hz Press Input Range Down multiple times Set the input range to 10 mV Press Sensitivity Down multiple times Set the sensitivity to 10 mV 3 Wait at least 10 seconds then record the reading of R yellow 4 Use the front panel to make the following adjustments Press Couple Select DC coupling 5 Wait 10 sec...

Page 203: ... touch Recall default Touch Confirm 2 Use the front panel to make the following adjustments Touch Fint to display the internal frequency keypad Enter a frequency of 1 0 kHz Touch Ampl to display the sine out amplitude keypad Enter an amplitude of 1 0 V 3 The value of R yellow should be 1 000 V within 2 4 Use the front panel to make the following adjustments Press Couple Select DC coupling Press A ...

Page 204: ...d be configured as i Reset press blue shift key then Reset ii SETACV RNDM press blue S then 3 times then then 2 times then Enter iii ACV press ACV iv a for RANGE 1 press blue R then 1 then Enter iv b for RANGE 0 1 press blue R then 0 1 then Enter iv c for RANGE 0 01 press blue R then 0 01 then Enter Procedure 1 PRESET press Save Recall then touch Recall default Touch Confirm 2 Amplitude accuracy i...

Page 205: ...6 Frequency response is checked at frequencies above 1 kHz The sine amplitude is set to 100 mV for all frequencies The test frequencies are listed below Test Frequencies 10 kHz 100 kHz 500 kHz a Use the front panel to make the following adjustments Touch Fint to display the internal frequency keypad Enter the frequency from the table b Wait for the multimeter readings to stabilize Record the value...

Page 206: ...sed to set performance Lower Limits and Upper Limits for Amplitude Accuracy and Flatness iii On the Performance Test Record for Lower and Upper limits perform the multiplication indicated with the referenced value of Sine Output Amplitude and Flatness For example Assume result A is recorded as 0 4966 V The Lower Limit at 1V will be 0 99 A 0 99 0 4966 V 0 4916 V The Upper Limit at 1V will be 1 01 A...

Page 207: ...ed below Test Frequencies 1 0 kHz 10 kHz 100 kHz 500 kHz a Use the front panel to make the following adjustments Touch Ampl to display the amplitude keypad Enter the 100 mV Press Input Range Up Down Set the input range to 100 mV Press Sensitivity Up Down Set the sensitivity to 100 mV b Set the sine output to the frequency in the table Touch Fint to display the internal frequency keypad Enter the f...

Page 208: ...E Sine Out BNC This means that each measurement will nominally be 50 of the programmed sine amplitude Procedure 1 PRESET press Save Recall then touch Recall default Touch Confirm 2 Use the front panel to make the following adjustments Touch Fint to display the internal frequency keypad Enter a frequency of 1 0 kHz Press Filter Slope adv multiple times Select 24 dB oct 3 For each of the amplitudes ...

Page 209: ...Press External Trig Select Pos TTL Press Config Touch Data1 Display to highlight the green data source Touch Fext to choose external reference frequency for Data1 Touch Close Press Screen Layout multiple times to set the screen to show half screen strip chart Touch the green vertical tile for Fe and touch autoscale to expand the trace Touch the white horizontal scale tile Time to display the horiz...

Page 210: ...f the specified 24 inch cable will introduce an additional 6 9 ns of propagation delay between sine output and signal input at 500 kHz this corresponds to 1 25 of additional phase delay Procedure 1 PRESET press Save Recall then touch Recall default Touch Confirm 2 Use the front panel to make the following adjustments Touch Fint to display the internal frequency keypad Enter a frequency of 1 0 kHz ...

Page 211: ... Fint to display the internal frequency keypad Enter the frequency from the table b Wait for the readings to stabilize Record the value of θ orange c Repeat steps 4a and 4b for all frequencies in the table 5 This completes the phase accuracy test Enter the results of this test in the test record at the end of this section ...

Page 212: ...puts repeat steps 2a through 2e a Connect the CH1 or CH2 output to the DVM Set the DVM to a 20 V range b Use the front panel to make the following adjustments Press the CH1 or CH2 Output Offset knob Turn the offset on Make sure the OFFSET LED is on Press and hold the CH1 or CH2 Output Offset knob Display the X or Y offset keypad c For each of the offsets in the table below repeat steps 2d and 2e O...

Page 213: ...reen Layout multiple times Set the screen to show 8 big numerical bar graphs Press Config Touch Data1 Display to highlight the green data source Touch In 1 to choose Aux input 1 for Data1 Repeat this to assign In2 In4 to Data2 Data4 5 For Aux Inputs 1 2 3 and 4 repeat steps 5a through 5e a Connect Aux Out 1 to the Aux Input under test with a BNC cable b For each output voltage in table 3c above re...

Page 214: ...uency of 1 0 kHz Press Input Range Down multiple times Set the input range to 10 mV Press Sensitivity Down multiple times Set the sensitivity to 100 nV Press Filter Slope adv Select 12 dB oct Press Couple Select DC coupling Press Ground Select shield Ground Press Config to display the data configuration screen Touch Data1 Display to highlight the green data source Touch Xnoise to choose Xnoise for...

Page 215: ...00 mV DC _______ 0 500 mV Common Mode Rejection Frequency Reading Upper Limit 1 kHz _______ 30 µV Sine Output Amplitude and Flatness Sine Output Ampl Lower Limit Reading Upper Limit 1 00 V 0 490 V A _______ 0 5100 V 300 mV 147 0 mV B _______ 153 0 mV 100 mV 49 0 mV C _______ 51 0 mV 30 mV 14 70 mV D _______ 15 30 mV 10 0 mV 4 98 mV E _______ 5 10 mV 1 00 mV 0 490 mV F _______ 0 510 mV Sine Ampl Fr...

Page 216: ...2 H ______ Amplitude Linearity Input Range Sine Out Ampl Lower Limit Reading Upper Limit 1 V 1 0000 Vrms 0 99 A ______ _______ 1 01 A ______ 100 00 mVrms 0 99 C ______ _______ 1 01 C ______ 10 000 mVrms 0 99 E ______ _______ 1 01 E ______ 1 0000 mVrms 0 99 F ______ _______ 1 01 F ______ Frequency Accuracy Input Frequency Lower Limit Reading Upper Limit 9 9990 kHz 9 9987 kHz _______ 9 9992 kHz Phas...

Page 217: ..._______ 10 10 V 5 000 4 95 V _______ 5 05 V 0 000 0 010 V _______ 0 010 V 5 000 5 05 V _______ 4 95 V 10 000 10 10 V _______ 9 90 V Output Voltage Lower Limit Reading Upper Limit AUX OUT 3 10 000 9 90 V _______ 10 10 V 5 000 4 95 V _______ 5 05 V 0 000 0 010 V _______ 0 010 V 5 000 5 05 V _______ 4 95 V 10 000 10 10 V _______ 9 90 V Output Voltage Lower Limit Reading Upper Limit AUX OUT 4 10 000 9...

Page 218: ...0 V _______ 9 90 V 5 000 5 05 V _______ 4 95 V 0 000 0 010 V _______ 0 010 V 5 000 4 95 V _______ 5 05 V 10 000 9 90 V _______ 10 10 V Input Voltage Lower Limit Reading Upper Limit AUX IN 4 10 000 10 10 V _______ 9 90 V 5 000 5 05 V _______ 4 95 V 0 000 0 010 V _______ 0 010 V 5 000 4 95 V _______ 5 05 V 10 000 9 90 V _______ 10 10 V Input Noise Frequency Input Range Sensitivity Reading Upper Limi...

Page 219: ... V A R305 or R302 dc offset voltage trim is injected at the fully differential summing junctions for U204 which also provides CMRR trimming for the voltage preamp front end Programmable gain blocks around U402 and U404 implement the SR860 Input Range setting with U406 driving the rear panel Signal Mon after all programmable gain is added The main analog signal is driven differentially through R428...

Page 220: ...ay control is implemented with U201 U711 All power rails for the circuit board are re regulated from the main power supply 16V to 15V and 5V with U212 U214 linear regulators Auxiliary I O The rear panel auxiliary I O circuit supports the 4 AUX OUT and 4 AUX IN analog signals Outputs are received differentially referenced to system ground from the motherboard on header J1 through difference amplifi...

Page 221: ... end module Preamp Ref In and Sine Out through the regulator board signals come in via J7 and are bussed to pins 4 5 8 and 9 of the power control connectors J2 J6 and J8 While each set of related voltage rails has a separate ground network all of these grounds are loosely tied to chassis ground through resistors R31 R36 10 kΩ each to avoid any supplies drifting away during testing before connectio...

Page 222: ...204 Circuit Description Appendix H SR860 DSP Lock in Amplifier Partial schematics follow this page ...

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