Srs-labs SR850 Manual do Utilizador

MODEL SR850 DSP Lock-In Amplifier 1290-D Reamwood Avenue Sunnyvale, California 94089 Phone: (408) 744-9040 • Fax: (408)

SR850 DSP Lock-In Amplifier1-8DTRC (?) i {, j} 6-11 Set (Query) theFull (i=0), Top (i=1) or Bottom (i=2) Display Trace to trace j (1,2,3,4).DSCL (?) {

4-18Screen Display

4-19 W R S T M N O J G H I B C A D E F Y Z P U Q V X K LAUTORESERVEAUTOGAINAUTOPHASEAUTOSCALEALT EXP ENTER0_CURSORMAX/MIN.1 3CURSORSETUP2

4-20[DISPLAY/SCALE]Select full screen or split screen display, settingsor input/output monitor, and display scaling.[AUX OUTPUTS]Program the four Aux

4-21[PAUSE/RESET] will erase the data bufferwhenever data acquisition is Paused or Done.To clear a buffer while a scan is in progress, twopresses of t

4-22saved as well. When a trace is recalled from disk,the marks are recalled as well. Existing marks arereplaced with the recalled marks.[CURSOR MAX/M

4-23Pressing [AUTO SCALE] when a chart graph isthe active display will automatically set the verticalrange and center value to display the entire rang

4-24Keypad

4-25 FUSEPULLAUX OUTAUX IN12344321X YTTL OUTIEEE-488 STD PORTPC KEYBOARD (8088)PRINTER PORTRS232 (DCE)Fuse : 1A @100/120V & 1/2A @ 220/240VTRIG

4-26REAR PANEL BNC CONNECTORSAUX IN 1-4 (A/D Inputs)These are auxiliary analog inputs which can bedigitized by the SR850. The range is -10V to +10Vand

4-27Rear PanelTRIG INThis TTL input may be used to trigger data sam-ples and/or to start data acquisition. When thesample rate is set to Trigger, samp

SR850 DSP Lock-In Amplifier1-9RDAT 6-18 Recall the Trace Data from the file specified by FNAM to the active display's trace buffer.RSET 6-18 Reca

4-28Rear Panel

SR850 MENUS5-1Default Settings 5-2Reference and Phase 5-3Internal/External ReferenceInternal Osc Frequency and AmplitudeInternal SweepsExternal Refere

5-2SR850 MenusREFERENCE / PHASEPhase 0.000°Reference Source InternalReference Slope SineHarmonic 1Sine Output 1.000 VrmsInternal Frequency 1.000 kHzIn

REFERENCE AND PHASE MENUSine OutputHarmonic12.345 deg.Rotate90 deg.InternalRef Frequency50.000 Hz# 10.100 V rmsRef. SourceRef. PhaseSine OutputHar

5-4Reference and Phase MenuReference Source The Reference Source key selects the source of the lock-in reference.Turn the knob to select the desired s

5-5Reference and Phase MenuInternal Sweep When the reference source is Internal Sweep, the SR850'ssynthesized internal reference is used as the r

5-6Reference and Phase MenuHarmonic The SR850 can detect signals at harmonics of the reference frequency.The SR850 multiplies the input signal with di

INPUT AND FILTERS MENUFloatGroundingCurrent GainSourceA A-BIGround1M 100MLine NotchesOut Line2xLineBothCouplingAC DCGroundingSourceCurrent GainINPUTFI

5-8Input and Filters MenuThe current gain determines the input current noise as well as the inputbandwidth. The 100 MΩ gain has 10 times lower noise b

GAIN AND TIME CONSTANT MENUMaxReserveFilter dB/oct.Sensitivity10 mV f.s.Manual41 dB100 mS1.2 Hz6 1218 2460 dB gainSynchronousOff< 200HzManual R

SR850 DSP Lock-In Amplifier1-10SERIAL POLL STATUS BYTE (6-28)bit name usage0 SCN No data is being acquired1 IFC No command execution in progress2 ERR

5-10Gain and Time Constant MenuReserve This key selects either maximum, minimum or manual dynamic reserve.When the reserve is maximum, the SR850 autom

5-11Gain and Time Constant Menusignal will obscure the signal at the reference and make detection difficultif not impossible. See the SR850 Basics sec

5-12Gain and Time Constant Menu<165 10 s<175 30 s12 dB/oct DC gain (dB) min time constant<55 10 µs<75 30 µs<95 100 µs<115 300 µs<

5-13Gain and Time Constant MenuFilter dB/oct This key selects the low pass filter slope (number of poles). Each polecontributes 6 dB/oct of roll off.

5-14Gain and Time Constant MenuUse of the synchronous filter results in a reduction in amplituderesolution.

OUTPUT AND OFFSET MENUFront PanelCH1 CH2Source:XX Y ROffset:0.00%Expand:1Auto:Offset & ExpandX, Y or R OutputCH1 or CH2 OutputOffsetOUTPUTOFFSETEx

5-16Output and Offset MenuOutput Offset and Expand The X, Y and R outputs may be offset and expanded. See the SR850Basics section for a complete discu

TRACE AND SCAN MENU1 ShotScan LengthSample RateTrace1 2 3 4X11❊Do Not StoreStore1 Hz16000.04:26:40.0LoopSingle Shot/LoopSample RateStore/Do Not StoreD

5-18Trace and Scan MenuThe A, B and C parameters may be set to the quantities X, Y, R, θ,Xnoise, Ynoise, Rnoise, Aux Inputs 1-4 (on the rear panel), F

5-19Trace and Scan MenuAliasing effects can occur whenever the trace being sampled containssignals at frequencies greater than twice the sample rate.

GETTING STARTEDThe sample measurements described in this section are designed to acquaint the first time user with theSR850 DSP Lock-In Amplifier. Do

5-20Trace and Scan Menu

DISPLAY AND SCALE MENUFullSettingsInput/OutputSingleDisplay ScaleMonitorFormatUp/DownTopBottomType: ChartTrace: 1±1.000 e0@ 0.010 S /divCenterFormatFu

5-22Display and Scale MenuFull, Top or Bottom Display Pressing this key selects which display's type, trace and scaling will beadjusted and displ

5-23Display and Scale MenuSeconds/div Chart graphs have a horizontal scale which determines how much of thedata buffer will be displayed. The horizont

5-24Display and Scale Menu

AUX OUTPUTS MENULinearFixedAux. OutputVoltage1 2 3 4Log2.000 VTrigger Starts?No YesTrigger Starts?VoltageFixedAux Output 1, 2, 3 or 4AUXOUTPUTS Log o

5-26Aux Outputs MenuVoltage This menu box displays the fixed voltage at the selected aux output. Thismenu box is only displayed if the output is Fixe

5-27Aux Outputs MenuA log sweep from a higher voltage to a lower voltage is just the reverseprogression as the sweep from lower to higher. More time w

5-28Aux Outputs Menu

Cursor Seek The cursor marker searches the data points within the cursor region forthe maximum or minimum data value, or calculates the mean of thereg

2-2Getting Started

5-30Cursor Setup MenuCursor Width This function selects the width of the cursor region defined by the verticaldashed lines on the chart display. Curso

Insert Mark Marks are normally added to the data buffer by pressing the [MARK] keywhile a scan is in progress. When a scan is paused or completed, mar

5-32Edit Mark MenuEdit Mark This key activates a submenu which allows marks to be labelled andviewed. This key will select the nearest mark to the lef

MATH MENUMathSmooth:Fit:Calc:Stats:FitSmoothMATHStatsCalcMath The Math menu is used to smooth, fit, change and analyze trace data.Math functions only

5-34Math MenuPressing a smoothing key will smooth the data within the active chart dis-play with the corresponding width. A width of 25 points means t

5-35Math MenuFit The Fit sub menu allows the user to fit one of three curves to the datawithin the active chart display - lines, exponentials, and Gau

5-36Math Menure-entered, the View Parameters function will re-display the best fit curveand the parameter window. Both the Do Fit and View Parameters

5-37Math Menu Pressing any key to continue will remove the parameter window while leaving the best fit curve on the display. Pressing another key to

5-38Math MenuCalc The Calculation sub menu allows the user perform simple arithmetic cal-culations with data displayed in the active chart. Operations

5-39Math MenuArgument Type The +, -, x, / operations require a second argument. The Argument Typefunction selects between a constant argument and anot

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

5-40Math MenuStats The Stats sub menu calculates a variety of statistical information about achart display calculation region defined by the Left and

Disk Keys Each softkey in this menu activates a submenu. The submenus aredescribed in detail on the following pages.DiskUtils:SettingsRecall:Save:Data

Disk Menu5-42Save Data The Save Data submenu is used to save the trace data which is on theactive chart display to the disk. Save Data Pressing this k

5-43Disk Menu Catalog On/Off This key toggles the file catalog display screen on and off. The file catalog display lists all files currently in the r

Disk Menu5-44Recall Data The Recall Data submenu is used to recall data from a binary disk fileinto the trace which is displayed by the active display

5-45Disk MenuRecall Data Pressing this key will recall the trace data and instrumentstate from the file specified in the File Name field. If the file

Disk Menu5-46Save Settings The Save Settings submenu is used to save the lock-in settings to a diskfile. The settings include all parameters which are

5-47Disk MenuRecall Settings The Recall Settings submenu is used to recall the lock-in settings from adisk file. The settings include all parameters w

Disk Menu5-48Disk Utilities The Disk Utilities submenu contains the Format Disk and Erase File func-tions. These functions should be used with care si

SYSTEM SETUP MENU5-49System Setup The System Setup menu is used to configure the system parameters.The Settings submenu configures the printer, plotte

2-45. Press the <Rotate 90 deg> softkey.Press the <deg.> softkey. Use the knob to adjust the phase shift until Yis zero and X is equal to

5-50System Setup MenuSettings Keys The Settings menu consists of two menus, with each key activating asubmenu. Use the More and Return softkeys to tog

5-51System Setup MenuReturn:ViewQueues:SetupSetupOutput ToGPIB:RS232:RS-232 GPIBOveride Remote ?GPIB AddressReturnView QueuesWord LengthOutput To RS23

5-52System Setup MenuSetup GPIB The Setup GPIB key activates the GPIB parameters submenu. GPIBinstrument address and Remote Overide are set in this su

5-53System Setup MenuOutput ToRS-232SetupRS232:Return:GPIBReceive Queue:Transmit Queue:*IDN? Stanford_Research_Systems,SR850,s/n00001,ver001 Press

5-54System Setup MenuAlarmsReturn:On OffKey ClickOn OffSetup Sound The Setup Sound key activates the sound submenu. Key click andalarms are enabled an

5-55System Setup MenuDefinePens:Return:RS232 GPIBSlowPlot SpeedBaud RatePlot Mode9600 bdFastSetup Plotter The Setup Plotter submenu configures the SR8

5-56System Setup MenuPlotter Addr. If the Plot Mode is GPIB, then the Plotter Address mustbe set. The Plotter Address may be entered from thekeypad or

5-57System Setup MenuEpsonReturn:Printer TypeHPFileSetup Printer The Setup Printer menu is used to select the type of printer attached tothe parallel

5-58System Setup MenuReturn:Down:MoveUp:Left:Right:Setup Screen The Setup Screen submenu is used to adjust the position of the displayon the screen. T

5-59System Setup Menu03 / 15 / 9103 : 45 : 12DateReturn:TimeSetup Time The Setup Time key activates the clock/calendar submenu. The time andda

2-59. Press <Sensitivity>Use the knob to change the sensitivity to50 mV.Change the sensitivity back to 20 mV.10. Press <Time Constant>Use

5-60System Setup Menu

5-61System Setup MenuPlot All The Plot All key generates a plot of the entire display, including the scaleand marker information. In single display fo

5-62System Setup Menu

5-63System Setup MenuReturn:About theSR850:About SRS:OperatingHints:CommandList:StatusBytes:About the SR850 This key displays the SR850 specifications

5-64System Setup Menu

5-65System Setup MenuKeypad Test This key activates the keypad test screen. The keypad test screen dis-plays a map of the keypad with each key represe

5-66System Setup MenuDisk Drive Test Pressing this key activates the disk drive test screen. Continuing withthis test will destroy any data on the dis

SR850 is in a remote state (front panel lockedout). The LOC indicator is on when the front panelis active (Local Mode). The SRQ indicator is onwhen th

6-2Remote Programmingcomputer is ready to receive. If either buffer over-flows, both buffers are cleared and an errorreported. The present value of a

6-3Remote ProgrammingDETAILED COMMAND LISTThe four letter mnemonic in each command sequence specifies the command. The rest of the sequence con-sists

2-613. Press [GAIN/TC]Press <Synchronous> to select <200 Hz. Display the Gain and Time Constant menu again.This turns on synchronous filterin

6-4Remote ProgrammingREFERENCE and PHASE COMMANDSPHAS (?) {x} The PHAS command sets or queries the reference phase shift. Theparameter x is the phase

6-5Remote ProgrammingHARM (?) {i} The HARM command sets or queries the detection harmonic. Thisparameter is an integer from 1 to 32767. The HARM i com

6-6Remote ProgrammingINPUT and FILTER COMMANDSISRC (?) {i} The ISRC command sets or queries the input configuration. The parame-ter i selects A (i=0),

6-7Remote ProgrammingGAIN and TIME CONSTANT COMMANDSSENS (?) {i} The SENS command sets or queries the sensitivity. The parameter iselects a sensitivit

6-8Remote ProgrammingTime constants greater than 30s may NOT be set if theharmonic x ref. frequency (detection frequency) exceeds 200 Hz. Timeconstant

6-9Remote ProgrammingOUTPUT and OFFSET COMMANDSFOUT (?) i {, j} The FOUT command sets or queries the front panel (CH1 and CH2)output sources. The para

6-10Remote ProgrammingTRACE and SCAN COMMANDSTRCD (?) i {, j, k, l, m} The TRCD command sets or queries the trace definitions. The parameteri selects

6-11Remote ProgrammingDISPLAY and SCALE COMMANDSASCL The ASCL command auto scales the active display. This command isjust like pressing the [AUTO SCAL

6-12Remote ProgrammingDHZS (?) i {, j} The DHZS command sets or queries the display horizontal scale. Theparameter i selects the Full (i=0), Top (i=1)

6-13Remote ProgrammingCURSOR COMMANDSCSEK (?) {i} The CSEK command sets or queries the cursor seek mode of the activedisplay. The parameter i selects

2-7DISPLAYS and TRACES This measurement is designed to use the internal oscillator and an external signal source to explore some ofthe display types.

6-14Remote ProgrammingMARK COMMANDSMARK The MARK command is just like pressing the [MARK] key. A mark will beplaced in the data buffer at the next sa

6-15Remote ProgrammingAUX INPUT and OUTPUT COMMANDSOAUX? i The OAUX? command queries the Aux Input values. The parameter iselects an Aux Input (1, 2,

6-16Remote ProgrammingMATH COMMANDSThe math functions operate on the trace which is graphed in the active display. If the display type is polar,then t

6-17Remote ProgrammingCALC The CALC command starts the calculation selected by the COPR com-mand. This may take some time. Use a status query command

6-18Remote ProgrammingSTORE AND RECALL FILE COMMANDSWhen using file commands, the status byte should be queried after the command is sent to check if

6-19Remote ProgrammingSETUP COMMANDSOUTX (?) {i} The OUTX command sets the output interface to RS232 (i=0) or GPIB(i=1). The OUTX i command should be

6-20Remote ProgrammingPNGD (?) {i} The PNGD command sets or queries the grid pen number. The pennumber is in the range of 1 to 6.PNAL (?) {i} The PNAL

6-21Remote ProgrammingPRINT and PLOT COMMANDSPRSC The PRSC command will print the screen display to a printer attached tothe rear panel parallel print

6-22Remote ProgrammingFRONT PANEL CONTROLS and AUTO FUNCTIONSSTRT The STRT command starts or resumes a scan (and sweep). This func-tion is the same as

6-23Remote ProgrammingDATA TRANSFER COMMANDSOUTP ? i The OUTP? i command reads the value of X, Y, R or . The parameteri selects X (i=1), Y (i=2), R (

2-8Displays and TracesHighlight the internal oscillator frequency.By setting the lock-in reference 0.2 Hz away fromthe signal frequency, the X and Y o

6-24Remote Programmingand θ are also recorded at a single instant. Thus reading X,Y OR R,θyields a coherent snapshot of the output signal. If X,Y,R an

6-25Remote Programmingtransfer does not pause between bytes. The receiving interface mustalways be ready to receive the next byte. In general, using b

6-26Remote ProgrammingThe parameter i selects a trace (1, 2, 3 or 4) and is required. If Trace i isnot stored, then an error occurs. Points are read f

6-27Remote Programmingtalker and the controlling interface a listener. Remember, the first transferwill occur with the very first point in the scan. I

6-28Remote ProgrammingINTERFACE COMMANDS❊RST The ❊RST command resets the SR850 to its default configurations. Thecommunications setup is not changed.

6-29Remote ProgrammingSTATUS REPORTING COMMANDSThe Status Byte definitions follow this section.❊CLS The ❊CLS command clears all status registers. The

6-30Remote ProgrammingSTATUS BYTE DEFINITIONSThe SR850 reports on its status by means of four status bytes: the Serial Poll Status byte, the Standard

6-31Remote ProgrammingSERVICE REQUESTS (SRQ)A GPIB service request (SRQ) will be generated whenever a bit in both the Serial Poll Status byte AND Seri

6-32Remote ProgrammingLIA STATUS BYTE bit name usage0 INPUT/RESRV Set when an INPUT or RESRV overload isdetected.1 FILTR Set when a FILTR overload is

6-33Remote ProgrammingEXAMPLE PROGRAM 1Using Microsoft C (v5.1) with the National Instruments GPIB card on the IBM PC.To successfully interface the SR

2-9Displays and Traces[AUTO SCALE] automatically scales the activedisplay. In this case, the trace data is moving andautoscaling may not do a very sat

6-34Remote Programming/* function prototypes */void main(int, char *[]);void txLia(char *);void initGpib(char *);void setupLiaForSweep(void);void

6-35Remote ProgrammingprintOutBinaryResults(); /* format and print the results */printf("\n%d bytes received.\nPress <Enter> to continue.&q

6-36Remote Programmingprintf("\n\n");for (i=0;i<10;i++)printf("%d %e\n",i,rfBuf[i]); /* this is simple since the values are alr

6-37Remote ProgrammingtxLia("DSCL0,.5;DOFF0,.5"); /* set scale from 0 to 1 V */txLia("DHZS0,11"); /* set 10s/div horizontal */prin

6-38Remote Programming

6-39Remote ProgrammingEXAMPLE PROGRAM 2Using Microsoft QUICKBASIC (v4.5) with the National Instruments GPIBcard on the IBM PC.To successfully interfac

6-40Remote Programming' Look for device named "LIA". Use IBCONF to configure the device "LIA" as above.' Assign the devi

6-41Remote ProgrammingWRT$ = "FAST2;STRD"CALL TXLIA(LIA%, WRT$)' Get FAST mode data.' The 100 sec sweep at 64 Hz has 64*100 + 1 po

6-42Remote ProgrammingEXPONENT% = RXBUF%(2 * I% + 1) - 124' compute the floating point valueR = MANTISSA% * 2! ^ EXPONENT%PRINT "I =";

PERFORMANCE TESTSIntroductionThe performance tests described in this sectionare designed to verify with a high degree of confi-dence that the unit is

2-10Displays and TracesWith a TTL reference signal, the slope needs to beset to either rising or falling edge.The signal vector on the polar graph wil

7-2Performance TestsGeneral InstallationPOWERMake sure that the power entry module on the rearpanel is set for the AC line voltage in your areaand tha

7-3Performance TestsNecessary EquipmentThe following equipment is necessary to completethe performance tests. The suggested equipmentor its equivalent

7-4Performance Tests

7-5Performance Tests1. Self TestsThe self tests check the lock-in hardware. These are functional tests and do not relate to the specifications.These t

7-6Performance Tests

7-7Performance 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

7-8Performance Tests

7-9Performance Tests3. Common Mode RejectionThis test measures the common mode rejection of the lock-in. SetupWe will use the internal oscillator sine

7-10Performance Tests

7-11Performance Tests4. Amplitude Accuracy and FlatnessThis test measures the amplitude accuracy and frequency response.SetupWe will use the frequency

2-11Displays and TracesUsing the keypad, enter a phase shift which is45° greater than the displayed phase shift.At a measured phase shift of 45°, trac

7-12Performance Testsa) Set the AC calibrator to the amplitude shown in the table.b) Press <Sensitivity>Use the knob to select the sensitivity f

7-13Performance Tests5. Amplitude LinearityThis test measures the amplitude linearity. This tests how accurately the lock-in measures a signal smaller

7-14Performance Tests3) For each of the amplitudes listed below, perform steps 3a through 3c.AC Calibrator Amplitudes R Output Expand1.0000 Vrms 1100.

7-15Performance Tests6. Frequency AccuracyThis test measures the frequency accuracy of the lock-in. This tests the accuracy of the frequency counterin

7-16Performance Tests

7-17Performance Tests7. Phase AccuracyThis test measures the phase accuracy of the lock-in. Due to the design of the lock-in, the phase accuracycan be

7-18Performance Tests

7-19Performance Tests8. Sine Output Amplitude Accuracy and FlatnessThis test measures the amplitude accuracy and frequency response of the internal os

7-20Performance Testsc) Press[GAIN/TC]<Sensitivity>Use the knob to select 1 V.[REF/PHASE]<Sine Output>[1] [ENTER]d) Press<Ref. Frequenc

7-21Performance 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

2-12Displays and Traces

7-22Performance Testsc) For each output voltage in the table below, repeat steps 5d and 5e.Output Voltages-10.000-5.0000.0005.00010.000d) Press<Vol

7-23Performance Tests10. Input NoiseThis test measures the lock-in input noise.SetupConnect a 50Ω termination to the A input. This grounds the input s

7-24Performance Tests

SR850 Performance Test Record Serial Number Tested By Firmware Revision Date Equipment Used 1. Self Tests Test Pass Fail Power On Tests ____ _

SR850 Performance Test Record 5. Amplitude LinearitySensitivity Calibrator Ampl. Lower Limit Reading Upper Limit1 V 1.0000 Vrms 0.9900 V _______ 1.01

SR850 Performance Test Record 9. DC Outputs and Inputs (continued)Output Offset Lower Limit Reading Upper LimitCH2 -100.00 9.960 V _______ 10.040 V-5

SR850 Performance Test Record 9. DC Outputs and Inputs (continued)Input Voltage Lower Limit Reading Upper LimitAUX1 -10.000 -10.040 V _______ -9.960

SR850 SERVICE8-1CAUTIONPotentially lethal voltages are present in this instrument. This unit is to be servicedby qualified service personnel only. The

8-2SR850 Service

8-3SR850 ServiceAdjusting the DC Offset and Common Mode Rejection1. The DC Offset and CMRR adjustments affect each other and must be done together. Th

2-13OUTPUTS, OFFSETS and EXPANDSThis measurement is designed to use the internal oscillator to explore some of the basic lock-in outputs. Youwill need

8-4SR850 ServiceIf the R reading (top display) is less than 1 mV, then proceed to the next step. If the reading isgreater than 1 mV, adjust the Voltag

8-5SR850 Service[GAIN/TC]<Sensitivity>Rotate the knob to select 100 mV full scaleIf the R reading (top display) is less than 1 mV, then proceed

8-6SR850 ServiceAdjusting the Notch Filters1. The Notch filter frequency and depth adjustments must be done together. This procedure requiresa BNC cab

8-7SR850 ServicePress[AUTO PHASE]The bottom display should read 0.0°.7. Press [INPUT/FILTERS]<Line Notches> to select Line[GAIN/TC]<Sensitivi

8-8SR850 Service

Power Supply BoardAnalog Input BoardDSP Logic BoardCPU BoardCAUTIONAlways disconnect the power cord andwait at least one minute before open-ing the un

9-2Circuit Description

9-3Circuit DescriptionThe CPU board contains the microprocessorsystem. All display, front panel, disk, and comput-er interfaces are on this board. MIC

9-4Circuit DescriptionSPEAKERThe speaker is driven by a timer on the 80C186.The timer outputs a square wave which is enabledby U602B and drives the sp

9-5Circuit DescriptionThe following description refers to the +5V_Psupply but describes the +5V_I supply as well.The main pass transistor is Q5. The b

2-144. Press [REF/PHASE]Press <Sine Output>Press [.] [5] [ENTER]5. Press [OUTPUT/OFFSET]Press <Auto Offset>Press <Offset>Press [4] [

9-6Circuit Description

9-7Circuit DescriptionOVERVIEWThe DSP LOGIC BOARD takes a digital input fromthe A/D Converter on the Analog Input Board andperforms all of the computa

9-8Circuit Descriptiontransmit port each cycle. The transmit port oper-ates at twice the frequency of the receive port. TheDSP writes to the other cha

9-9Circuit DescriptionOVERVIEWThe Analog Input Board provides the very impor-tant link between the user's input signal and theDSP processor. From

9-10Circuit Descriptiona rate of 256 kHz. One channel is dedicated to theinput signal. The other channel reads one of theAux A/D inputs. The Aux input

PARTS LIST 9-11 Power Supply Board Parts List Ref. SRS Part No. Value Description C 1 5-00124-526 5600U Capacitor, Elect

Parts List 9-12 Ref. SRS Part No. Value Description D 30 3-00479-301 MUR410 Diode D 31 3-004

Parts List 9-13 Ref. SRS Part No. Value Description R 37 4-00522-407 243 Resistor, Metal Film, 1/8W, 1%, 50PPM R 38 4-00517-407 3.5

Parts List 9-14 Ref. SRS Part No. Value Description C 153 5-00023-529 .1U Cap, Monolythic Ceramic, 50V, 20%, Z5U C 154 5-0

Parts List 9-15 Ref. SRS Part No. Value Description C 384 5-00100-517 2.2U Capacitor, Tantalum, 35V, 20%, Rad C 385 5-0

2-156. Connect the DVM to the X output on the rearpanel.7. Connect the DVM to the CH1 output on thefront panel again.Press <Expand>Press [1] [EN

Parts List 9-16 Ref. SRS Part No. Value Description C 655 5-00225-548 .1U AXIAL Capacitor, Ceramic, 50V,+80/-20% Z5U AX C 656 5-0

Parts List 9-17 Ref. SRS Part No. Value Description N 603 4-00463-421 82X4 Res. Network, SIP, 1/4W,2% (Isolated) N 604 4-0

Parts List 9-18 Ref. SRS Part No. Value Description R 213 4-00317-407 422 Resistor, Metal Film, 1/8W, 1%, 50PPM R 214 4-00652-407 1.

Parts List 9-19 Ref. SRS Part No. Value Description RX623 4-00053-401 200 Resistor, Carbon Film, 1/4W, 5% T 201 6-00137-601 15

Parts List 9-20 Ref. SRS Part No. Value Description U 301 3-00087-340 LF347 Integrated Circuit (Thru-hole Pkg) U 302 3-0

Parts List 9-21 Ref. SRS Part No. Value Description C 153 5-00023-529 .1U Cap, Monolythic Ceramic, 50V, 20%, Z5U C 180 5-0

Parts List 9-22 Ref. SRS Part No. Value Description C 463 5-00023-529 .1U Cap, Monolythic Ceramic, 50V, 20%, Z5U C 480 5-0

Parts List 9-23 Ref. SRS Part No. Value Description P 101 4-00015-445 100K Pot, Multi-Turn, Side Adjust P 102 4-0

Parts List 9-24 Ref. SRS Part No. Value Description R 225 4-00321-407 1.74K Resistor, Metal Film, 1/8W, 1%, 50PPM R 226 4-0

Parts List 9-25 Ref. SRS Part No. Value Description R 371 4-00763-407 14.0K Resistor, Metal Film, 1/8W, 1%, 50PPM R 372 4-0

2-16Press <Source>Use the knob to select Trace1.8. Press [TRACE/SCAN]Press the second softkey, next to the tracedefinition, to highlight the X.U

Parts List 9-26 Ref. SRS Part No. Value Description TP102 1-00143-101 TEST JACK Vertical Test Jack TP103 1-0

Parts List 9-27 Ref. SRS Part No. Value Description U 381 3-00130-340 5532A Integrated Circuit (Thru-hole Pkg) U 386 3-0

Parts List 9-28 Ref. SRS Part No. Value Description C 902 5-00003-501 10P Capacitor, Ceramic Disc, 50V, 10%, SL C 903 5-0

Parts List 9-29 Ref. SRS Part No. Value Description C 1041 5-00225-548 .1U AXIAL Capacitor, Ceramic, 50V,+80/-20% Z5U AX C 1042 5

Parts List 9-30 Ref. SRS Part No. Value Description Q 703 3-00021-325 2N3904 Transistor, TO-92 Package Q 705 3-0

Parts List 9-31 Ref. SRS Part No. Value Description U 207 3-00343-340 74ALS32 Integrated Circuit (Thru-hole Pkg) U 208 3-0

Parts List 9-32 Ref. SRS Part No. Value Description U 908 3-00040-340 74HC157 Integrated Circuit (Thru-hole Pkg) X 101 6-0

Parts List 9-33 Ref. SRS Part No. Value Description Z 0 0-00259-021 4-40X1/2"PP Screw, Panhead Phillips Z 0 0-

Parts List 9-34 Ref. SRS Part No. Value Description Z 0 1-00206-133 20 PIN DRA Connector, Male, Right Angle Z 0 1-00208

Parts List 9-35 Ref. SRS Part No. Value Description Z 0 9-00267-917 GENERIC Product Labels Miscell

2-17SCANS and SWEEPSThis measurement is designed to use the internal oscillator to explore some of the basic lock-in functions.You will need BNC cable

Parts List 9-36 NOTICE: Schematics may not show current part numbers or values. Refer to parts list for current part numbers or values.

TABLE OF CONTENTS 1-1 GENERAL INFORMATION Safety and Preparation for Use 1-3 Specifications 1-5 Abridged Command List 1-7 GETTING STA

2-184. Press [DISPLAY/SCALE]Press the <Type/Trace> softkey to select theTrace number.Use the knob to select Trace 3.5. Press [REF/PHASE]Press &l

2-19Press <Sample Rate>Use the knob to select 32 Hz.Press <Scan Length>Press [1] [0] [0] [ENTER]Press <1 Shot/Loop> to select 1 Shot

2-2010. Press [DISPLAY/SCALE]Press <Format> to select Single.Press <Type> Use the knob to select Chart.Press <Type> again to highlig

2-21Press <Cursor Seek> to select Min.Use the knob to read the frequencies of thenotch filter zeroes or minimums.13. Press [DISPLAY/SCALE]Press

2-22Scans and Sweeps16. When the scan is complete, press[TRACE/SCAN].Press <1 Shot/Loop> to select Loop.Press [PAUSE/RESET]Press [START/CONT] to

2-23USING THE DISK DRIVEThe disk drive on the SR850 may be used to store 3 types of files.1. Data FileThis includes the data in the active display tra

2-243. Press [AUTO PHASE]4. Press [DISPLAY/SCALE]Press <Format> to select Single display.Press <Type> Use the knob to adjust the display t

2-258. Press [DISK]Press <Disk Utils>Press <Disk Format>Press <Return>Press <Data Save>Press <File Name>Press [ALT] Pres

2-26The Disk DrivePress <Data Save>11. Press <Catalog> to select On.Press <Return>12. Press [PAUSE RESET]13. Press <Data Recall&g

2-27Use the knob to select the Chart display.Press <Full, Top or Bottom> to select Bottom.Use the knob to select the Chart display forthe bottom

Table of Contents 1-2 Interface Ready and Status 6-2 GET (Group Execute Trigger) 6-2 DETAILED COMMAND LIST 6-3 Reference and Phase

2-28Press <Data Recall>Press [AUTO SCALE]This recalls the data file from disk and stores it inthe active display trace. The active display trace

2-29STORING AND RECALLING SETTINGS1. Turn the lock-in on while holding down the [←](backspace) key. Wait until the power-on testsare completed. Discon

2-30Press <Catalog>Use the knob to select the settings file whichyou just saved.6. Press <Settings Recall>Press [GAIN/TC]Display the disk

2-31AUX OUTPUTS and INPUTSThis measurement is designed to illustrate the use of the Aux Outputs and Inputs on the rear panel. You willneed BNC cables

2-325. Disconnect the DVM from Aux Out 1. ConnectAux Out 1 to Aux In 1 on the rear panel. 6. Press [TRACE/SCAN]Press the second softkey, next to the t

2-3310. Press [DISPLAY/SCALE]Press <Type / Trace> to highlight the type ofthe top display.Use the knob to change the display type toChart.1 V to

2-34Aux Outputs and Inputs

2-35TRACE MATHThis example is designed to familiarize the user with the trace math functions in the lock-in. You will needBNC cables and a 50Ω termina

2-36Use the knob to select 50 nV.4. Press [TRACE/SCAN]Press <Sample Rate>Use the knob to change the sample rate to16 Hz.5. Press [DISPLAY/SCALE]

2-37Press <Return> twice.8. Press <Smooth>Press <17 point>Press [CURSOR]Use the knob to move the cursor past the leftedge of the gra

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

2-38Press <Do Calc.>Press [AUTO SCALE]Use the knob to select log10.Press <Do Calc.>Use the knob to select ❊.Press <Argument Type> to

2-39Trace MathPress <1 Shot/Loop> to select 1 Shot.13. Connect the Sine Out to the A input using aBNC cable.Wait until the value of X reaches 1

2-40Trace MathPress <Left Limit>Use the knob to position the cursor 3 divisionsto the right of the left limit.Press <Right Limit>Move the

2-41Trace MathMove the cursor past the left edge of thegraph to pan the data window until the signaldecay becomes visible again.20. Press [MATH]Press

2-42Trace Math

SR850 BASICSLock-in amplifiers are used to detect and measurevery small AC signals - all the way down to a fewnanovolts! Accurate measurements may be

3-2SR850 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

3-3SR850 BasicsSo what exactly does the SR850 meas-ure?Fourier's theorem basically states that anyinput signal can be represented as the sum ofma

3-4SR850 Basics

3-5SR850 BasicsThe functional block diagram of the SR850 DSPLock-In Amplifier is shown below. The functions inthe gray area are handled by the digital

1-4

3-6SR850 Basics

3-7SR850 BasicsA lock-in amplifier requires a reference oscillatorphase-locked to the signal frequency. In general,this is accomplished by phase-locki

3-8SR850 Basicsdegrees of noise. This shows up at the output asnoise in phase or quadrature measurements.Phase noise can also cause noise to appear at

3-9SR850 BasicsThe SR850 multiplies the signal with the referencesine waves digitally. The amplified signal is con-verted to digital form using a 16 b

3-10SR850 Basics

3-11SR850 BasicsRemember, the output of the PSD contains manysignals. Most of the output signals have frequen-cies which are either the sum or differe

3-12SR850 Basicsneed to be at 0.001 Hz!In the SR850, synchronous filters are available atdetection frequencies below 200 Hz. At higher fre-quencies, t

3-13SR850 BasicsThe SR850 has X and Y outputs on the rear paneland Channel 1 and 2 (CH1 and CH2) outputs onthe front panel. X and YThe X and Y rear pa

3-14SR850 Basicsdeviations can be expanded up to 100 timesbefore they exceed full scale (at 1 mV sensitivity).The analog output with offset and expand

3-15SR850 Basicsoutput voltages of X, Y or R in trace output calcu-lations. For example, a trace which is defined as Xand output through CH1 or CH2 in

SR850 DSP LOCK-IN AMPLIFIER1-5SPECIFICATIONSSIGNAL CHANNELVoltage Inputs Single-ended (A) or differential (A-B).Current Input 106 or 108 Volts/Amp.Ful

3-16SR850 Basics

3-17SR850 BasicsWe've mentioned dynamic reserve quite a bit inthe preceding discussions. It's time to clarifydynamic reserve a bit.What is d

3-18SR850 Basicsfrequencies than within the operating range. Whilethis may be a nice specification, removing noise atfrequencies very far from the ref

3-19SR850 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

3-20SR850 Basicsmeasurements in the vicinity of the notch frequen-cies. These filters have a finite range of attenua-tion, generally 10 Hz or so. Thus

3-21SR850 BasicsIn order to achieve the best accuracy for a givenmeasurement, care must be taken to minimize thevarious noise sources which can be fou

3-22SR850 BasicsCurrent Input (I)The current input on the SR850 uses the A inputBNC. Voltage or current input is chosen in theINPUT menu. The current

3-23SR850 BasicsRandom noise finds its way into experiments in avariety of ways. Good experimental design canreduce these noise sources and improve th

3-24SR850 Basics

3-25SR850 BasicsIn addition to the intrinsic noise sources discussedin the previously, there are a variety of externalnoise sources within the laborat

SR850 DSP Lock-In Amplifier1-6INPUTS AND OUTPUTSChannel 1 Output X, R, θ, or Trace 1-4. Traces are defined as A•B/C or A•B/C2 where A, B,and C are sel

3-26SR850 BasicsCures for inductively coupled noise include:1) Removing or turning off the interferingnoise source.2) Reduce the area of the pick-up l

3-27SR850 BasicsLock-in amplifiers can be used to measure noise.Noise measurements are generally used to char-acterize components and detectors.The SR

3-28SR850 BasicsWhich method you use depends upon the require-ments of the experiment.R noiseThe quantity Rn can be somewhat hard to under-stand. For

POWER BUTTONThe SR850 is turned on by pushing in the powerbutton. The video display may take a few secondsto warm up and become visible. Adjust the br

4-2The main area of the display is occupied by theoutput display(s). Both single and dual trace dis-plays are available. In addition, each display can

4-3Front PanelCh1 & Ch2 OutputsThe Channel 1 and Channel 2 outputs can be con-figured to output a voltage from -10 V to +10 Vproportional to X, Y,

4-4Front Panel

4-5Lock-in ParametersMaxFr= 100.00 HzFull Scale = 10 mVTrace 1Dyn Reserve = 0 dB100 mS12 dB/oct Line 2xLin AC AXX = 9.7284 mV± 10.000 e-3 0.0

4-6Screen DisplayDATA TRACESThe SR850 collects and displays data in the formof traces. There are four data traces which may bedefined. Each trace is d

4-7Up/DownSingleMonitorTrace 2Display ScaleFormatXX = 9.7284 mV± 10.000 e-3 0.0 VYcenter = 0.0 ± 50.00 e-3 VTrace 1SettingsInput/Outpu

SR850 DSP Lock-In Amplifier1-7COMMAND LISTVARIABLES i,j,k,l,m Integersf Frequency (real)x,y,z Real Numberss StringREFERENCE and PHASE page description

4-8Screen Display

4-9Center value and Trace UnitsTrace Offset and Expand IndicatorsXX = 9.7284 mV± 10.000 e-3 0.0 VTrace 1Trace Identifier Trace DefinitionFull sc

4-10X Axis (0°)Y Axis (90°)Signal VectorTrace Offset and Expand IndicatorsPOLAR GRAPHSThe polar graph is a convenient way to view magnitude and phase.

4-11center = 0.0 ± 50.00 e-3 V10 S /divY 36.000 S 58.332 e-30.000 STrace Identifier Trace Definition Cursor ReadoutVertical rangeVer

4-12Data ScrollingThe chart display acts like a strip chart recorderwhere the pen is drawing the most recent data.For example, if the sample rate is 1

4-13Screen DisplayTRACE SCANS, SWEEPS & ALIASINGTrace and Scan parameters are selected in theTRACE/SCAN menu.Trace StorageHaving defined up to fou

4-14Screen Displaythe scan length is only meaningful is parametersare being swept. Once the trace buffer has loopedaround, the oldest point (at any ti

4-15SETTINGS & INPUT/OUTPUT MONITORThe upper two lines of the screen are the monitordisplay (see the screen on pg. 4-5). The lock-insettings (sens

4-16STATUS INDICATORSThere are a number of status indicators which aredisplayed at the bottom of the screen. Theseinclude the scan, unlock, and overlo

4-17allowed), press the [HELP] key. LOC is on when-ever local front panel control is allowed (usuallyon).SRQThis indicator is on whenever a GPIB Servi