DSP TP104-plus Specifications

DSP Lock-In Amplifiermodel SR8301290 D Reamwood AvenueSunnyvale, CA94089 USAPhone: (408) 744-9040 • Fax: (408) 744-9049www.thinkSRS.com •e-mail: info@

SR830 DSP Lock-In Amplifier1-9SERIAL POLL STATUS BYTE (5-21)bit name usage0 SCN No data is being acquired1 IFC No command execution in progress2 ERR

5-17Remote Programmingfers on the RS232 interface is not recommended.The parameter i selects the display buffer (i=1, 2) and is required. Pointsare re

5-18Remote Programmingalways be ready to receive the next byte. In general, using binary trans-fers on the RS232 interface is not recommended.The para

5-19Remote ProgrammingINTERFACE COMMANDS❊RST The ❊RST command resets the SR830 to its default configurations. Thecommunications setup is not changed.

5-20Remote ProgrammingSTATUS REPORTING COMMANDSThe Status Byte definitions follow this section.❊CLS The ❊CLS command clears all status registers. The

5-21Remote ProgrammingSTATUS BYTE DEFINITIONSThe SR830 reports on its status by means of four status bytes: the Serial Poll Status byte, the Standard

5-22Remote ProgrammingSERVICE REQUESTS (SRQ)A GPIB service request (SRQ) will be generated whenever a bit in both the Serial Poll Status byte AND Seri

5-23Remote ProgrammingLIA STATUS BYTE bit name usage0 INPUT/RESRV Set when an Input or Amplifier overload isdetected.1 FILTR Set when a Time Constant

5-24Remote Programming

5-25Remote ProgrammingEXAMPLE PROGRAM 1Using Microsoft C (v5.1) with the National Instruments GPIB card on the IBM PC.To successfully interface the SR

5-26Remote Programmingvoid main(int, char *[]);void txLia(char *);void initGpib(char *);void setupLia(void);void printOutBinaryResults(void);void prin

SR830 DSP Lock-In Amplifier1-10

5-27Remote Programmingi=(int)ibcnt; /* save total number of bytes read */txLia("PAUS"); /* pause the data storage so no new points are taken

5-28Remote Programmingvoid printOutIEEEResults(void){/* prints the first 10 values of R transferred in IEEE floating point format by the SR830 */int i

5-29Remote ProgrammingtxLia("SRAT10; SEND0"); /* set 64 Hz sample rate, stop at end */txLia("DDEF1,1,0; DDEF2,1,0"); /* set CH1=R,

5-30Remote Programming

5-31Remote ProgrammingUSING SR530 PROGRAMS WITH THE SR830The SR830 responds to most SR530 programming commands. This allows the SR830 to drop into an

5-32Remote ProgrammingH The SR830 does not sense the pre-amplifier. This command is emulat-ed and always returns 0.I {n} Change the remote/local statu

5-33Remote ProgrammingIf m=2:T2,0 changes the slope to 6 dB/oct, time constant not changed.T2,1 changes the time constant to 100 ms with 12 dB/oct slo

5-34Remote Programming

PERFORMANCE TESTSIntroduction The performance tests described in this section are designed to verifywith a high degree of confidence that the unit is

6-2Performance TestsSpurious ≤ -55 dBcTTL SYNC availableRecommended SRS DS3352. AC CalibratorFreq Range 10 Hz to 100 kHzAmplitude 1 mV to 10 VAccuracy

GETTING STARTEDThe sample measurements described in this section are designed to acquaint the first time user with theSR830 DSP Lock-In Amplifier. Do

6-3Performance Tests1. Self TestsThe self tests check the lock-in hardware. These are functional tests and do not relate to the specifications.These t

6-4Performance Tests

6-5Performance Tests2. DC OffsetThis test measures the DC offset of the input.SetupConnect a 50Ω terminator to the A input. This shorts the input so t

6-6Performance Tests

6-7Performance Tests3. Common Mode RejectionThis test measures the common mode rejection of the lock-in. SetupWe will use the internal oscillator sine

6-8Performance Tests

6-9Performance Tests4. Amplitude Accuracy and FlatnessThis test measures the amplitude accuracy and frequency response.SetupWe will use the frequency

6-10Performance Testsb) Press [Sensitivity Up/Dn]Select the sensitivity from the table.c) Wait for the R reading to stabilize. Record the value of R f

6-11Performance Tests5. Amplitude LinearityThis test measures the amplitude linearity. This tests how accurately the lock-in measures a signal smaller

6-12Performance Tests

2-2Getting Started

6-13Performance Tests6. Frequency AccuracyThis test measures the frequency accuracy of the lock-in. This tests the accuracy of the frequency counterin

6-14Performance Tests

6-15Performance Tests7. Phase AccuracyThis test measures the phase accuracy of the lock-in. Due to the design of the lock-in, the phase accuracycan be

6-16Performance Tests

6-17Performance Tests8. Sine Output Amplitude Accuracy and FlatnessThis test measures the amplitude accuracy and frequency response of the internal os

6-18Performance Testsd) Press[Freq]Use the knob to set the internal oscillator frequency to the value in the table.e) Wait for the R reading to stabil

6-19Performance Tests9. DC Outputs and InputsThis test measures the DC accuracy of the DC outputs and inputs of the lock-in.SetupWe will use the digit

6-20Performance Testsc) For each output voltage in the table below, repeat steps 3d and 3e.Output Voltages-10.000-5.0000.0005.00010.000d) Use the knob

6-21Performance Tests10. Input NoiseThis test measures the lock-in input noise.SetupConnect a 50Ω termination to the A input. This grounds the input s

6-22Performance Tests

2-3THE BASIC LOCK-INThis measurement is designed to use the internal oscillator to explore some of the basic lock-in functions.You will need BNC cable

SR830 Performance Test Record Serial Number Tested ByFirmware Revision DateEquipment Used1. Self TestsTest Pass FailDATA ____ ____BATT ____ ____PROG _

SR830 Performance Test Record 5. Amplitude LinearitySensitivity Calibrator Ampl. Lower Limit Reading Upper Limit1 V 1.0000 Vrms 0.9900 V _______ 1.01

SR830 Performance Test Record 9. DC Outputs and Inputs (continued)Output Offset Lower Limit Reading Upper LimitCH2 -100.00 9.980 V _______ 10.020 V-5

SR830 Performance Test Record 9. DC Outputs and Inputs (continued)Input Voltage Lower Limit Reading Upper LimitAUX IN 1 -10.000 -10.040 V _______ -9.

CAUTIONAlways disconnect the power cord andwait at least one minute before open-ing the unit. Dangerous power supplyvoltages may be present even after

7-2Circuit Description

7-3Circuit DescriptionThe CPU board contains the microprocessorsystem. All display, front panel, disk, and comput-er interfaces are on this board. MIC

7-4Circuit DescriptionPOWER SUPPLYCAUTION: Dangerous voltages are present onthis circuit board whenever the instrument isattached to an AC power sourc

7-5Circuit DescriptionOVERVIEWThe DSP LOGIC BOARD takes a digital input fromthe A/D Converter on the Analog Input Board andperforms all of the computa

7-6Circuit Descriptiontransmit port each cycle. The transmit port oper-ates at twice the frequency of the receive port. TheDSP writes to the other cha

2-4Use the knob to adjust the phase shift until Yis zero and X is equal to the positiveamplitude.Press [Auto Phase]6. Press [Freq]Use the knob to adju

7-7Circuit DescriptionOVERVIEWThe Analog Input Board provides the very impor-tant link between the user's input signal and theDSP processor. From

7-8Circuit Descriptiona rate of 256 kHz. One channel is dedicated to theinput signal. The other channel reads one of theAux A/D inputs. The Aux inputs

Parts List7-9PARTS LISTDSP Logic Board Parts ListRef No. SRS Part No. Value Component DescriptionC 101 5-00060-512 1.0U Cap, Stacked Metal

C 283 5-00100-517 2.2U Capacitor, Tantalum, 35V, 20%, Rad C 290 5-00023-529 .1U Cap, Monolythic Ceramic, 50V, 20%, Z5U

7-11C 603 5-00038-509 10U Capacitor, Electrolytic, 50V, 20%, Rad C 604 5-00239-562 680P Cap., NPO Monolitic Ceramic, 50v, 5% RaC 610

N 503 4-00333-421 10KX5 Res. Network, SIP, 1/4W,2% (Isolated) N 601 4-00767-420 270X8 Resistor Network, DIP, 1/4W,2%,8 Ind

7-13R 220 4-00139-407 10.0M Resistor, Metal Film, 1/8W, 1%, 50PPM R 221 4-00130-407 1.00K Resistor, Metal Film, 1/8W, 1%, 50PP

TP203 1-00143-101 TEST JACK Vertical Test Jack TP204 1-00143-101 TEST JACK Vertical Test Jack

7-15U 606 3-00499-343 SR850 U606 GAL/PAL, I.C. U 608 3-00411-340 74HC273 Integrated Circuit (Thru-hole Pkg)

C 371 5-00148-545 1000P Capacitor, Monolythic Ceramic, COG, 1% C 372 5-00148-545 1000P Capacitor, Monolythic Ceramic, COG, 1% C 381 5-00148-545 1

2-511. Press the [Slope/Oct] key until 6 dB/oct isselected.Press [Slope/Oct] again to select 12 dB/oct.Press [Slope/Oct] twice to select 24 db/oct.Pre

7-17K 103 3-00444-335 HS-211-5 Relay K 104 3-00196-335 HS-212S-5 Relay

R 205 4-00321-407 1.74K Resistor, Metal Film, 1/8W, 1%, 50PPM R 207 4-00380-407 6.34K Resistor, Metal Film, 1/8W, 1%, 50PPM

Parts List7-19R 372 4-00700-407 1.62K Resistor, Metal Film, 1/8W, 1%, 50PPM R 373 4-00763-407 14.0K Resistor, Metal Film, 1/8W

7-20TP407 1-00143-101 TEST JACK Vertical Test Jack TP408 1-00143-101 TEST JACK Vertical Test Jack

7-21Z 0 0-00043-011 4-40 KEP Nut, Kep Z 0 0-00187-021 4-40X1/4PP Screw, Panhead Phillips Z 0 0-00243

7-22C 1017 5-00225-548 .1U AXIAL Capacitor, Ceramic, 50V,+80/-20% Z5U AX C 1018 5-00225-548 .1U AXIAL Capacitor, Ceramic, 50V,+80/-20% Z5U AX

7-23PC1 7-00512-701 SR810/830 CPU Printed Circuit Board Q 3 3-00021-325 2N3904 Transistor, TO-92 Package

7-24U 401 3-00551-341 128KX8-70 STATIC RAM, I.C. U 402 3-00551-341 128KX8-70 STATIC RAM, I.C.

7-25C 10 5-00219-529 .01U Cap, Monolythic Ceramic, 50V, 20%, Z5U C 11 5-00219-529 .01U Cap, Monolythic Ceramic, 50V, 20%, Z5U

7-26D 31 3-00547-310 RED COATED LED, Coated Rectangular D 32 3-00547-310 RED COATED LED, Coated Rectangular

2-6The Basic Lock-in

7-27D 88 3-00575-311 GREEN MINI LED, Subminiature D 89 3-00575-311 GREEN MINI LED, Subminiature

7-28J 2003 1-00181-165 9 PIN STRAIGHT Connector, D-Sub, Female JP4 1-00171-130 34 PIN ELH Connector, Male

7-29Z 0 0-00089-033 4” Tie Z 0 0-00097-040 #6 FLAT Washer, Flat Z 0 0-0

7-30Z 0 6-00212-630 1”X.25”CYL Ferrite Beads Z 0 6-00214-630 .5”X.25”CYL Ferrite Beads Z 0 7-00

Parts List7-31

2-7X, Y, R and θThis measurement is designed to use the internal oscillator and an external signal source to explore some ofthe display types. You wil

2-8X, Y, R and θshould now oscillate at about 0.2 Hz (the accuracyis determined by the crystals of the generator andthe lock-in).The default Channel 1

GENERAL INFORMATIONSafety and Preparation for Use 1-3Specifications 1-5Abridged Command List 1-7GETTING STARTEDYour First Measurements 2-1The Basic Lo

2-9OUTPUTS, OFFSETS and EXPANDSThis measurement is designed to use the internal oscillator to explore some of the basic lock-in outputs. Youwill need

2-105. Press [Channel 1 Auto Offset]Press [Channel 1 Offset Modify]Use the knob to adjust the X offset to 40.0%Press [Channel 1 Expand] to select x10.

2-116. Connect the DVM to the X output on the rearpanel.7. Connect the DVM to the CH1 OUTPUT on thefront panel again.Press [Channel 1 Output] to selec

2-12Outputs, Offsets and Expands

2-13STORING and RECALLING SETUPSThe SR830 can store 9 complete instrument setups in non-volatile memory.When the power is turned on with the [Setup] k

2-14Storing and Recalling Setups

2-15AUX OUTPUTS and INPUTSThis measurement is designed to illustrate the use of the Aux Outputs and Inputs on the rear panel. You willneed BNC cables

2-166. Press [Channel 2 Display] to select AUX IN 3.7. Connect Aux Out 1 to Aux In 3 on the rearpanel. Change the Channel 2 display to measure AuxInpu

SR830 BASICSLock-in amplifiers are used to detect and measurevery small AC signals - all the way down to a fewnanovolts! Accurate measurements may be

3-2SR830 BasicsThis is a very nice signal - it is a DC signal propor-tional to the signal amplitude. Narrow band detectionNow suppose the input is mad

Table of ContentsTESTINGIntroduction 6-1Preset 6-1Serial Number 6-1Firmware Revision 6-1Test Record 6-1If A Test Fails 6-1Necessary Equipment 6-1Front

3-3SR830 BasicsSo what exactly does the SR830 measure?Fourier's theorem basically states that any inputsignal can be represented as the sum of ma

3-4SR830 Basics

3-5SR830 BasicsThe functional block diagram of the SR830 DSPLock-In Amplifier is shown below. The functions inthe gray area are handled by the digital

3-6SR830 Basics

3-7SR830 BasicsA lock-in amplifier requires a reference oscillatorphase-locked to the signal frequency. In general,this is accomplished by phase-locki

3-8SR830 Basicsjitter means that the average phase shift is zerobut the instantaneous phase shift has a few milli-degrees of noise. This shows up at t

3-9SR830 BasicsThe SR830 multiplies the signal with the referencesine waves digitally. The amplified signal is con-verted to digital form using a 16 b

3-10SR830 Basics

3-11SR830 BasicsRemember, the output of the PSD contains manysignals. Most of the output signals have frequen-cies which are either the sum or differe

3-12SR830 Basicsincreasingly useful the lower the reference fre-quency. Imagine what the time constant wouldneed to be at 0.001 Hz!In the SR830, synch

SAFETY AND PREPARATION FOR USECAUTIONThis instrument may be damaged if operatedwith the LINE VOLTAGE SELECTOR set for thewrong AC line voltage or if t

3-13SR830 BasicsThe SR830 has X and Y outputs on the rear paneland Channel 1 and 2 (CH1 and CH2) outputs onthe front panel. X and Y Rear Panel Outputs

3-14SR830 BasicsThe analog output with offset and expand isOutput = (signal/sensitivity - offset) x Expand x10Vwhere offset is a fraction of 1 (50%=0.

3-15SR830 BasicsWe've mentioned dynamic reserve quite a bit inthe preceding discussions. It's time to clarifydynamic reserve a bit.What is d

3-16SR830 Basicssignal input attenuates frequencies far outside thelock-in's operating range (fnoise>>100 kHz). Inthese cases, the reserve

3-17SR830 BasicsA lock-in can measure signals as small as a fewnanovolts. A low noise signal amplifier is requiredto boost the signal to a level where

3-18SR830 Basicsthe measurement.Using either of these filters precludes makingmeasurements in the vicinity of the notch frequen-cies. These filters ha

3-19SR830 BasicsIn order to achieve the best accuracy for a givenmeasurement, care must be taken to minimize thevarious noise sources which can be fou

3-20SR830 BasicsCurrent Input (I)The current input on the SR830 uses the A inputBNC. The current input has a 1 kΩ input impe-dance and a current gain

3-21SR830 BasicsRandom noise finds its way into experiments in avariety of ways. Good experimental design canreduce these noise sources and improve th

3-22SR830 Basicsquencies more difficult.Other sources of 1/f noise include noise found invacuum tubes and semiconductors.Total noiseAll of these noise

1-4

3-23SR830 BasicsIn addition to the intrinsic noise sources discussedin the previously, there are a variety of externalnoise sources within the laborat

3-24SR830 BasicsCures for inductively coupled noise include:1) Removing or turning off the interferingnoise source.2) Reduce the area of the pick-up l

3-25SR830 BasicsLock-in amplifiers can be used to measure noise.Noise measurements are generally used to char-acterize components and detectors.The SR

3-26SR830 Basics

4-1Analog OutputsCH1 DisplayPower The power switch is on the rear panel. The SR830 is turned on by push-ing the switch up. The serial number (5 digit

4-2Front PanelKnob The knob is used to adjust parameters in the Reference display. Theparameters which may be adjusted are internal reference frequenc

4-3Front Paneltogether to enter the front panel test mode. Press [Phase] to decreasethe number of on LED's until all of the LED's are off. T

4-4Front PanelREFERENCE / PHASEPhase 0.000°Reference Source InternalHarmonic # 1Sine Amplitude 1.000 VrmsInternal Frequency 1.000 kHzExt Reference Tri

4-5Front PanelSignal Input and Filters[Input] The [Input] key selects the front end signal input configuration. The inputamplifier can be either a sin

4-6Front PanelINPUT OVLD The OVLD led in this section indicates an INPUT overload. This occursfor voltage inputs greater than 1.4Vpk (unless removed b

SR830 DSP LOCK-IN AMPLIFIER1-5SPECIFICATIONSSIGNAL CHANNELVoltage Inputs Single-ended (A) or differential (A-B).Current Input 106 or 108 Volts/Amp.Ful

4-7Front PanelSensitivity, Reserve and Time Constants[Sensitivity Up/Dn] The [Sensitivity Up] and [Sensitivity Down] keys select the full scale sen-si

4-8Front PanelThe actual dynamic reserves (in dB) for each sensitivity are listed below.Sensitivity Low Noise Normal High Reserve1 V 0 0 0500 mV 6 6 6

4-9Front Panelthe detection frequency is below 200 Hz and 100 s is the time constantand the frequency increases above 200 Hz, the time constant WILLch

4-10Front PanelRead the minimum time constant for this entry. For example, if the slopeis 12 dB/oct, the reserve is 64 dB, and the X expand is 10 (20

4-11Front PanelThe poles which are set by the time constant are the ones closest to thePSD's. For example, if the time constant is 100 ms with 12

4-12Front PanelCH1 Display and Output[Display] This key selects the Channel 1 display quantity. Channel 1 may displayX, R, X Noise, Aux Input 1 or Aux

4-13Front Panelkey. The Ratio indicator in the display is on to indicate a ratio measure-ment. Pressing this key until the AUX IN leds and the Ratio i

4-14Front Paneldisplay key ([Phase], [Freq], [Ampl], [Harm #] or [Aux Out]).[Auto Offset] Pressing this key automatically sets the X or R offset perce

4-15Front PanelCH2 Display and Output[Display] This key selects the Channel 2 display quantity. Channel 2 may displayY, θ, Y Noise, Aux Input 3 or Aux

4-16Front Paneloff returns the measurement to non-ratio mode.[Output] This key selects the CH2 OUTPUT source. The Channel 2 Output canprovide an analo

SR830 DSP Lock-In Amplifier1-6DISPLAYSChannel 1 4 1/2 digit LED display with 40 segment LED bar graph.X, R, X Noise, Aux Input 1 or 2. The display can

4-17Front Panel[Expand] Pressing this key selects the Y Expand. The expand can be 1 (noexpand), 10 or 100. If the expand is 10 or 100, the Expand indi

4-18Front PanelReference [Phase] Pressing this key displays the reference phase shift in the Referencedisplay. The knob may be used to adjust the pha

4-19Front Panel[+90°] and [-90°] The [+90°] and [-90°] keys add or subtract 90.000° from the referencephase shift. The phase does not need to be displ

4-20Front PanelIf the harmonic number is set to N, then the internal reference fre-quency is limited to 102 kHz/N.If an external reference is used and

4-21Front PanelAuto FunctionsPressing an Auto Function key initiates an auto function which may takesome time. The AUTO leds in the CH1 and CH2 displa

4-22Front Panelall possible input signals. In most cases, the following procedure shouldsetup the SR830 to measure the input signal.1.Press [AUTO GAIN

4-23Front PanelSetup[Save] Nine amplifier setups may be stored in non-volatile memory.To save asetup, press [Save] to display the buffer number (1..9)

4-24Front PanelInterface[Setup] Pressing the [Setup] key cycles through GPIB/RS232, ADDRESS,BAUD, PARITY and QUEUE. In each case, the appropriate para

4-25Front PanelHex ASCII Hex ASCII2A ❋ 34 42B + 35 52C , 36 62D - 37 72E . 38 830 0 39 931 1 3B ;32 2 3F ?33 3Hex ASCII Hex ASCII0A linefeed 50 P41 A

4-26Front PanelWARNING MESSAGESThe SR830 displays various warning messages whenever the operation of the instrument is not obvious. Thetwo tone warnin

SR830 DSP Lock-In Amplifier1-7COMMAND LISTVARIABLES i,j,k,l,m Integersf Frequency (real)x,y,z Real Numberss StringREFERENCE and PHASE page description

REAR PANELPower Entry Module The power entry module is used to fuse the AC line voltage input, selectthe line voltage, and block high frequency noise

4-28Rear PanelThese outputs are affected by the X and Y offsets and expands. Theactual outputs are X Output = (X/sensitivity - offset)xExpandx10VY Out

4-29Rear PanelUsing SRS Preamps When using either the SR550 or SR552, connect the power cable (stan-dard 9 pin D connectors) from the preamp to the re

4-30Rear Panel

completed.To help find program errors, the SR830 can dis-play its receive buffer on the displays. Use the[Setup] key to access the QUEUE display. Thel

5-2Remote Programmingbe determined by querying the SR830 for itsvalue. A query is formed by appending a questionmark "?" to the command mnem

5-3Remote ProgrammingDETAILED COMMAND LISTThe four letter mnemonic in each command sequence specifies the command. The rest of the sequence con-sists

5-4Remote ProgrammingREFERENCE and PHASE COMMANDSPHAS (?) {x} The PHAS command sets or queries the reference phase shift. Theparameter x is the phase

5-5Remote ProgrammingINPUT and FILTER COMMANDSISRC (?) {i} The ISRC command sets or queries the input configuration. The parame-ter i selects A (i=0),

5-6Remote ProgrammingGAIN and TIME CONSTANT COMMANDSSENS (?) {i} The SENS command sets or queries the sensitivity. The parameter iselects a sensitivit

SR830 DSP Lock-In Amplifier1-8DATA STORAGE page descriptionSRAT (?) {i} 5-13 Set (Query) the DataSample Rate to 62.5 mHz (0) through 512 Hz (13) or Tr

5-7Remote ProgrammingSYNC (?) {i} The SYNC command sets or queries the synchronous filter status. Theparameter i selects Off (i=0) or synchronous filt

5-8Remote ProgrammingDISPLAY and OUTPUT COMMANDSDDEF (?) i {, j, k} The DDEF command selects the CH1 and CH2 displays. The parameteri selects CH1 (i=1

5-9Remote ProgrammingAUX INPUT and OUTPUT COMMANDSOAUX? i The OAUX? command queries the Aux Input values. The parameter iselects an Aux Input (1, 2, 3

5-10Remote ProgrammingSETUP COMMANDSOUTX (?) {i} The OUTX command sets the output interface to RS232 (i=0) or GPIB(i=1). The OUTX i command should be

5-11Remote ProgrammingAUTO FUNCTIONSAGAN The AGAN command performs the Auto Gain function. This command isthe same as pressing the [Auto Gain] key. Au

5-12Remote ProgrammingDATA STORAGE COMMANDSData StorageThe SR830 can store up to 16383 points from both the Channel 1 and Channel 2 displays in an int

5-13Remote ProgrammingAliasing EffectsIn any sampled data stream, it is possible to sample a high frequency signal such that it will appear to be amuc

5-14Remote ProgrammingPAUS The PAUS command pauses data storage. If storage is already pausedor reset then this command is ignored.REST The REST comma

5-15Remote ProgrammingDATA TRANSFER COMMANDSOUTP ? i The OUTP? i command reads the value of X, Y, R or θ. The parameteri selects X (i=1), Y (i=2), R (

5-16Remote ProgrammingThe SNAP? command is a query only command. The SNAP? commandis used to record various parameters simultaneously, not to transfer