Stanford Research Systems SR865A User manual

Revision 2.04
Operation Manual
SR865A
4 MHz DSP Lock-in Amplifier
www.lambdaphoto.co.uk
Distribution in the UK & Ireland

SR865A DSP Lock-in Amplifier
Certification
Stanford Research Systems certifies that this product met its published specifications at
the time of shipment.
Warranty
This Stanford Research Systems product is warranted against defects in materials and
workmanship for a period of one (1) year from the date of shipment.
Service
For warranty service or repair, this product must be returned to a Stanford Research
Systems authorized service facility. Contact Stanford Research Systems or an authorized
representative before returning this product for repair.
Information in this document is subject to change without notice.
Copyright © Stanford Research Systems, Inc., 2015–2017. All rights reserved.
Document number 9-01715-903
Distribution in the UK & Ireland
Lambda Photometrics Limited
Lambda House Batford Mill
Harpenden Herts AL5 5BZ
United Kingdom
E: [email protected]
W: www.lambdaphoto.co.uk
T: [phone]
F: [phone]
Characterisation,
Measurement &
Analysis

Safety and Preparation For Use i
SR865A DSP Lock-in Amplifier
Safety and Preparation for Use
Warning
Dangerous voltages, capable of causing injury or death, are present
in this instrument. Use extreme caution whenever the instrument
covers are removed. Do not remove the covers while the unit is
plugged into a live outlet.
Line Voltage Selection
Caution
This instrument may be damaged if operated with the LINE VOLTAGE SELECTOR set
for the wrong ac line voltage or if the wrong fuse is installed.
The SR865A operates from a 100V, 120V, 220V, or 240V nominal ac power source
having a line frequency of 50 or 60 Hz. Before connecting the power cord, verify that the
LINE VOLTAGE SELECTOR card, located in the rear panel fuse holder, is set so that
the correct ac input voltage value is indicated by the white dot.
Conversion to other ac input voltages requires a change in the voltage selector card
position and fuse value. See Appendix F (page 177) for detailed instructions.
Line Fuse
Verify that the correct line fuse is installed before connecting the line 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 SR865A 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 which has a
properly connected protective ground. Power Cord
Grounding
A chassis grounding lug is available on the back panel of the SR865A. Connect a heavy
duty ground wire, #12AWG or larger, from the CHASSIS GROUND lug directly to a
facility earth ground to provide additional protection against electrical shock.
Grounded BNC shields are connected to the chassis ground. Do not apply any voltage to
the grounded shields. The A and B signal input shields are connected to chassis ground
through resistors and can tolerate up to 1 V of applied voltage.
GFCI (Ground Fault Circuit Interrupter)
GFCI protected outlets are often available in production and laboratory environments,
particularly in proximity to water sources. GFCI’s are generally regarded as an important
defense against electrocution. However, the use of GFCI in conjunction with the SR865A

ii Safety and Preparation For Use
SR865A DSP Lock-in Amplifier
must not be regarded as a substitute for proper grounding and careful system design.
GFCI’s must also be tested regularly to verify their functionality. Always consult an
electrician when in doubt.
Service
Do not attempt to service this instrument unless another person, capable of providing first
aid or resuscitation, is present.
Do not install substitute parts or perform any unauthorized modifications to this
instrument. Contact the factory for instructions on how to return the instrument for
authorized service and adjustment.
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 SR865A the stored charge may damage the front-end
amplifier. To avoid this problem, always discharge the cable and connect the PMT output
to the SR865A input before turning the PMT on.
Furnished Accessories
• Power Cord
• Operating Manual
Environmental Conditions
Operating
Temperature: +10 °C to +40 °C
(Specifications apply over +18 °C to +28 °C)
Relative Humidity: <90 % Non-condensing
Non-Operating
Temperature: −25°C to 65°C
Humidity: <95 % Non-condensing

Safety and Preparation For Use iii
SR865A DSP Lock-in Amplifier

iv Safety and Preparation For Use
SR865A DSP Lock-in Amplifier

Contents v
SR865A DSP Lock-in Amplifier
Contents
Safety and Preparation for Use i
Contents v
SR865A Specifications vii
SR865A Command List x
SR865A Status Bytes xv
Chapter 1 Getting Started 1
Introduction 1
SR865A Front Panel 2
SR865A Touchscreen 4
The Basic Lock-in 9
Using Displays 13
Sensitivity, Offset and Expand 20
Saving and Recalling Setups 25
Aux Outputs and Inputs 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 Measurements 58
Chapter 3 Operation 61
Introduction 61
Standard Settings 64
Signal Input 65
CH1 and CH2 Outputs: Offset, Ratio and Expand 71
Reference 74
Display 81
Cursor 83

vi Contents
SR865A DSP Lock-in Amplifier
Functions 85
Interface and Data 87
Setup 88
Rear Panel 96
Chapter 4 Programming 101
Introduction 101
Command Syntax 103
Reference Commands 106
Signal Commands 111
CH1/CH2 Output Commands 114
Aux Input and Output Commands 116
Auto Function Commands 117
Display Commands 118
Strip Chart Commands 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 Detection 175
Appendix F Fuse Installation and ac Line Select 177
Appendix G Performance Tests 181
Appendix H Circuit Description 201

Specifications vii
SR865A DSP Lock-in Amplifier
SR865A Specifications
Signal Channel
Voltage Inputs Single-ended (A) or differential (A−B)
Sensitivity (Output Scale) 1 nV to 1 V (voltage input)
1 fA to 1 μA (current input)
Input Impedance 10 MΩ+25 pF, ac (>1 Hz) or dc coupled
Input Range 10 mV to 1 V (peak); max input before overload
Gain Accuracy 1% below 200 kHz and 2% to 4 MHz (signal amplitude <30% of input range)
Input Noise 2.5 nV/√Hz above 1 kHz, 10 mV input range (typical)
CMRR Greater than 90 dB at 1 kHz (dc Coupled)
Harmonic Distortion −80 dB below 100 kHz, −60 dB above 100 kHz
Dynamic Reserve Greater than 120 dB
Current Input Ranges 1 μA or 10 nA
Reference Channel
Frequency Range 1 mHz to 4 MHz
Timebase 10 MHz In/Out phase locks the internal frequency to other SR865A units
Ext TTL Reference Minimum 2 V logic level, rising or falling edge
Ext Sine Reference 400 mV pk–pk minimum signal, ac coupled (>1 Hz)
Ext Reference Input Impedance 1 MΩor 50 Ω
Acquisition Time (2 cycles + 5 ms) or 40 ms, 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 2 MHz
Harmonic Detect Detect at N×fref where N≤99 and N×fref<4 MHz
Dual F Reference Detect at fdual = | fint − fext |
All frequencies less than 4 MHz for specified performance
Chopper Reference SR865A drives SR540 Chopper (via Aux Out 4) to lock the chopper to fint
Demodulator
dc Stability Digital output values have no offset drift
Time Constants 1 μs to 30 ks
Low Pass Filters Typical RC type filters or Advanced Gaussian/Linear Phase filters
Filter Slope 6, 12, 18, 24 dB/oct rolloffs
Synchronous Filter Available below 4 kHz
Harmonic Rejection −80 dB
Low Latency Output Rear panel BlazeX output with <2 μs delay (plus low pass filter rise/fall times)
Internal Oscillator
Frequency 1 mHz to 4 MHz
Frequency Accuracy 25 ppm + 30 μHz with internal timebase
External Timebase 10 MHz timebase input/output on rear panel
Frequency Resolution 6 digits or 0.1 mHz, whichever is greater

viii Specifications
SR865A DSP Lock-in Amplifier
Sine Output
Outputs Differential or Single-ended
Output Impedance 50 Ωsource
Amplitude 1 nVrms to 2 Vrms (specified amplitude is differential into 50 Ωloads)
Output amplitude is halved when used single-ended
Output amplitude is doubled into a high impedance load
Amplitude Resolution 3 digits or 1 nV, whichever is greater
dc Offset ±5 V, differential or common mode
Offset Resolution 3 digits or 0.1 mV, whichever is greater
Output Limit ±6 V, sum of dc offset and peak amplitude
Sync Logic level sync on rear panel (via BlazeX output)
Data
Data Channels 4 data channels are displayed and graphed (green, blue, yellow, orange)
Data Sources Each data channel can be assigned any of these data sources:
X, Y, R, θ, Aux In 1–4, Aux Out 1–2, Xnoise, Ynoise, Sine Out Amplitude, Sine Out
DC Level, reference phase, fint or fext
Data History All data sources are continuously stored at all chart display time scales.
The complete stored history of any data source can be displayed at any time.
Offset X, Y and R may be offset up to ±999% of the sensitivity
Ratio X, and Y may be ratioed by Aux In 3; R may be ratioed 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 following parameters may be scanned:
fint, Sine Out Amplitude, Sine Out DC Level, Aux Out 1 or 2.
FFT
Source Input ADC, demodulator output, or filter output
Record length 1024 bins
Averaging exponential rms
Inputs and Outputs
CH 1 Output Proportional to X or R, ±10 V full scale thru 50 Ω
CH 2 Output Proportional to Y or θ, ±10 V full scale thru 50 Ω
X and Y Outputs Proportional to X and Y, ±10 V full scale thru 50 Ω, rear panel
BlazeX Low latency output of X, ±2.0 V full scale or
logic level reference sync output, either thru 50 Ω
Aux Outputs 4 BNC D/A outputs, ±10.5 V thru 50 Ω, 1 mV resolution
Aux Inputs 4 BNC A/D inputs, ±10.5 V, 1 mV resolution, 1 MΩinput
Trigger Input TTL input triggers storage into the internal capture buffer
Monitor Output Analog output of the signal amplifier
HDMI Video output to external monitor or TV, 640x480/60 Hz.
Timebase Input/Output 1 Vrms 10 MHz clock to synchronize internal reference frequency to other units

Specifications ix
SR865A DSP Lock-in Amplifier
General
Interfaces IEEE488, RS-232, USB device (Test and Measurement Class) and 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

x Commands
SR865A DSP Lock-in Amplifier
SR865A Command List
Reference Commands
page
description
TBMODE(?) { AUTO | INternal | i }
106
Set the 10 MHz timebase
TBSTAT?
106
Query the current 10 MHz timebase ext (0) or int (1)
PHAS(?) { p } { UDEG | MDEG | DEG | URAD | MRAD | RAD }
106
Set the reference phase to p
APHS
106
Auto Phase
FREQ(?) { f } { HZ | KHZ | MHZ }
106
Set the reference frequency to f
FREQINT(?) { f } { HZ | KHZ | MHZ }
107
Set the internal reference frequency to f
FREQEXT?
107
Query the external reference frequency
FREQDET?
107
Query the detection frequency
HARM(?) { i }
107
Set harmonic detect to i
HARMDUAL(?) { i }
107
Set harmonic for dual reference mode to i
BLADESLOTS(?) {SLT6 | SLT30 | i }
108
Set the chopper blade number of slots
BLADEPHASE(?) { p } { UDEG | MDEG | DEG | URAD | MRAD |
RAD }
108
Set the chopper blade phase to p
SLVL(?) { v } { NV | UV | MV | V }
108
Set sine output amplitude to v
SOFF(?) { v } { NV | UV | MV | V }
108
Set sine output dc level to v
REFM(?) { COMmon | DIFference | i }
109
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(?) { VOLTage | CURRent | i }
111
Set input to voltage/current
ISRC(?) { A | A−B | i }
111
Set voltage input configuration
ICPL(?) { AC | DC | i }
111
Set voltage input coupling
IGND(?) { FLOat | GROund | i }
111
Set voltage input shield grounding
IRNG(?) { 1Volt | 300Mvolt | 100Mvolt | 30Mvolt | 10Mvolt | i }
111
Set voltage input range
ICUR(?) { 1MEG | 100MEG | i }
112
Set current input gain
ILVL?
112
Query the signal strength low to overload (0–4)
SCAL(?) { i }
112
Set sensitivity from 1V (0) to 1 nV (27)
OFLT(?) { i }
113
Set time constant from 1 μs (0) to 30 ks (21)
OFSL(?) { i }
113
Set filter slope from 6 dB (0) to 24 dB (3)
SYNC(?) { OFF | ON | i }
113
Turn synchronous filter off/on
ADVFILT(?) { OFF | ON | i }
113
Turn advanced filtering off/on
ENBW?
113
Query the equivalent noise bandwidth

Commands xi
SR865A DSP Lock-in Amplifier
CH1/CH2 Output Commands
page
description
COUT(?) [ OCH1 | OCH2 | j ] { , XY | RTHeta | i }
114
Set CH1/2 to (X or R)/(Y or θ)
CEXP(?) [ X | Y | R | j ] { , OFF | X10 | X100 | i }
114
Set CH1/2 expand
COFA(?) [ X | Y | R | j ] { , OFF | ON | i }
114
Turn CH1/2 output offset off/on
COFP(?) [ X | Y | R | j ] { , x }
114
Set CH1/2 output offset to x percent
OAUT [ X | Y | R | j ]
114
Auto Offset CH1/2
CRAT(?) [ X | Y | R | j ] { , OFF | ON | i }
115
Ratio Ch1/2 with Aux In 3 or 4
Aux Input and Output Commands
page
description
OAUX? [ j ]
116
Query Aux Input j (0–3)
AUXV(?) [ j ] { , v { NV | UV | MV | V } }
116
Set Aux Output j (0–3) voltage to v
Auto Function Commands
page
description
APHS
117
Auto Phase
ARNG
117
Auto Range
ASCL
117
Auto Scale
Display Commands
page
description
DBLK(?) { OFF | ON | i }
118
Turn front panel blanking off/on
DLAY(?) { TREnd | HISTory | BARHist | FFT | BARFft | BAREight | i }
118
Set Screen Layout
DCAP
118
Screen Shot to USB memory stick
CDSP(?) [ DAT1 | DAT2 | DAT3 | DAT4 | j ] { , parameter | i }
118
Assign parameter i to data channel j
CGRF(?) [ 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
GACT [ DAT1 | DAT2 | DAT3 | DAT4 | j ]
121
Auto scale with zero center channel j
GAUF [ DAT1 | DAT2 | DAT3 | DAT4 | j ]
121
Auto find for channel j
CGRF(?) [ DAT1 | DAT2 | DAT3 | DAT4 | j ] { , { OFF | ON | i } }
121
Turn channel j graph off/on
GLIV(?) { OFF | ON | i }
122
Turn strip chart off/on (pause/run)
PCUR(?) { i }
122
Move cursor to i (0=right, 639=left)
CURREL(?) {OFF | ON | i}
122
Set cursor relative or absolute mode
CURDISP(?) {i}
122
Set cursor horizontal mode to date/time or interval
CURBUG(?) {AVG | MAX | MIN | i}
122
Set cursor to mean / maximum / minimum
FCRW(?) { LIne | NARrow | WIde | i }
123
Set the cursor width
SCRY? [ DAT1 | DAT2 | DAT3 | DAT4 | STATus | j ]
123
Query the cursor data values
CURDATTIM?
123
Query the cursor horizontal position as date/time
CURINTERVAL?
124
Query the cursor horizontal position as interval

xii Commands
SR865A DSP Lock-in Amplifier
FFT Screen Commands
page
description
FFTR(?) { ADC | MIXer | FILTer | i }
125
Set FFT data source
FFTS(?) { i }
125
Set vertical scale from 1.0 dB (0) to 200 dB (7)
FFTO(?) { x }
125
Set top reference level
FAUT
126
FFT auto scale
FFTMAXSPAN?
126
Query maximum allowed frequency span in Hz/div
FFTSPAN(?) { x }
126
Set frequency span in Hz/div
FFTA(?) { AVG1 | AVG3 | AVG10 | AVG30 | AVG100 | i }
126
Set averaging
FFTL(?) { OFF | ON | i }
126
Turn FFT off/on (pause/live)
FCRW(?) { LIne | NARrow | WIde | i }
126
Set the cursor width
FCRX?
127
Query the FFT cursor frequency
FCRY?
127
Query the FFT cursor amplitude
Scan Commands
page
description
SCNPAR(?) { Fint | REFAmp | REFDc | OUT1 | OUT2 | i }
128
Set the scan parameter
SCNLOG(?) { LIN | LOG | i }
128
Set the scan type
SCNEND(?) { ONce | REpeat | UPdown | i }
128
Set the scan end mode
SCNSEC(?) { x }
128
Set the scan time to x seconds
SCNAMPATTN(?) {i}
128
Set the amplitude attenuator mode for scanning
SCNDCATTN(?) {i}
129
Set 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/end reference amplitude
SCNDC(?) [ BEGin | END | j ] { , v { NV | UV | MV | V } }
130
Set the begin/end reference dc level
SCNAUX1(?) [ BEGin | END | j ] { , v { NV | UV | MV | V } }
131
Set the begin/end AuxOut1 value
SCNAUX2(?) [ BEGin | END | j ] { , v { NV | UV | MV | V } }
131
Set the begin/end AuxOut2 value
Data Transfer Commands
page
description
OUTR? [ DAT1 | DAT2 | DAT3 | DAT4 | j ]
132
Query data channel j
OUTP? [ j ]
132
Query lock-in parameter j
SNAP? [ j, k ] { , l }
132
Query multiple lock-in parameters at once
SNAPD?
133
Query all 4 displayed parameters at once
Data Capture Commands
page
description
CAPTURELEN(?) { n }
136
Set the buffer length to n 1 kbyte blocks
CAPTURECFG(?) { X | XY | RT | XYRT | i }
136
Configure capture to X, XY, Rθor XYRθ(0–3)
CAPTURERATEMAX?
136
Query the maximum capture rate

Commands xiii
SR865A DSP Lock-in Amplifier
CAPTURERATE(?) { n }
136
Set the capture rate to (max rate)/2n
CAPTURESTART [ ONEshot | CONTinuous | i ] , [ IMMediate |
TRIGstart | SAMPpertrig | j ]
137
Start capture (OneShot or Cont) (HW trigger off/on)
CAPTURESTOP
137
Stop capture
CAPTURESTAT?
137
Query the capture buffer state
CAPTUREBYTES?
138
Query the number of bytes filled by captured data
CAPTUREPROG?
138
Query the length (kB) of captured data (after stop)
CAPTUREVAL? [ n ]
138
Query the nth sample (1, 2 or 4 values) (after stop)
CAPTUREGET? [ i ], [ j ]
139
Download binary capture buffer
Data Streaming Commands
page
description
STREAMCH(?) { X | XY | RT | XYRT | i }
140
Configure streaming to X, XY, Rθor XYRθ(0–3)
STREAMRATEMAX?
141
Query the maximum streaming rate
STREAMRATE(?) { n }
141
Set the streaming rate to (max rate)/2n
STREAMFMT(?) { i }
141
Set the streaming format to float32 (0) or int16 (1)
STREAMPCKT(?) { i }
141
Set packet size to 1024, 512, 256 or 128 bytes (0–3)
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(?) { BLazex | BIsync | UNIsync | i }
143
Select the BlazeX output
KEYC(?) { ON | MUte| i }
144
Turn sounds on or off
PRMD(?) { SCReen | PRNt | MONOchrome | i }
144
Set screen shot mode
SDFM(?) { CSV | MATfile | i }
144
Set data file type
FBAS(?) { s }
144
Set file name prefix
FNUM(?) { i }
144
Set file name suffix
FNXT?
145
Query next file name
DCAP
145
Screen shot
SVDT
145
Save data
Interface Commands
page
description
RST
146
Reset the unit to its default configuration
IDN?
146
Query the unit identification string
TST?
146
No-op, returns “0”
*OPC(?)
146
Operation Complete
LOCL(?) { i }
146
Set LOCAL (0), REMOTE (1) or LOCKOUT (2)
OVRM (?) { OFF | ON | i }
147
Set GPIB Overide Remote off (0) or on (1)

xiv Commands
SR865A DSP Lock-in Amplifier
Status Reporting Commands
page
description
CLS
148
Clear all status bytes
ESE(?) { j, } { i }
148
Set the standard event enable register
ESR? { j }
148
Query the 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

Commands xv
SR865A DSP Lock-in Amplifier
SR865A Status Bytes
Serial Poll Status Byte
bit
name
usage
0
unused
1
unused
2
ERR
An enabled bit in the error status byte has been set
3
LIA
An enabled bit in the LIA status byte has been set
4
MAV
The interface output buffer is non-empty
5
ESB
An enabled bit in the standard status byte has been set
6
SRQ
SRQ (service request) has occurred
7
unused
Standard Event Status Byte
bit
name
usage
0
OPC
Operation complete
1
INP
Input queue overflow
2
unused
3
QRY
Output queue overflow
4
EXE
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
SYNCOV
Sync filter overload
7
TRIG
Set when data storage is triggered
8
DAT1OV
Data Channel 1 output overload
9
DAT2OV
Data Channel 2 output overload
10
DAT3OV
Data Channel 3 output overload
11
DAT4OV
Data Channel 4 output overload
12
DCAPFIN
Display capture to USB stick completed
13
SCNST
Scan started
14
SCNFIN
Scan completed

xvi Commands
SR865A DSP Lock-in Amplifier
Error Status Byte
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)

Getting Started 1
SR865A DSP Lock-in Amplifier
Chapter 1
Getting Started
Introduction
The sample measurements described in this section are designed to acquaint the first time
user with the SR865A DSP Lock-In Amplifier. Do not be concerned that your
measurements do not exactly agree with these exercises. The focus of these measurement
exercises is to learn how to use the instrument. It is highly recommended that the first
time user step through some or all of these exercises before 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. Some also have a second italicized label. Press and hold
these knobs for 2 seconds to invoke the italicized function.
{Touch} Touchscreen buttons and icons are referred to in {curly} brackets.
Touchscreen buttons are used to adjust the data display as well as change
certain lock-in parameters.

2 Getting Started Chapter 1
SR865A DSP Lock-in Amplifier
SR865A Front Panel
The SR865A’s buttons and knobs are mainly used to configure the lock-in measurement,
while the touchscreen is mainly for data display. The touchscreen display is also used for
keypad entry.
Signal Path
The signal path settings configure input BNC’s, input gain, time constant and filters and
the sensitivity. Unlike previous generation lock-ins, the SR865A does not have a dynamic
reserve setting. The input range setting is simply the largest input signal before overload.
It is best to decrease the input range setting as much as possible without overload. This
increases the gain and utilizes more of the A/D converter’s range as 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 sensitivity should be viewed as an output function only.
Reference
The reference settings configure the lock-in reference frequency and source. In addition
to internal and external reference, the SR865A includes dual reference (detect at |fint −
fext|) and chop (lock an SR540 chopper TO the SR865A fint) modes.
The SR865A can be synchronized to an external 10 MHz frequency reference (from
another SR865A or other source). This allows multiple SR865A’s to run in phase sync
with each other in internal reference mode.