Page 1 DSP Lock-In Amplifier model SR830 1290 D Reamwood Avenue Sunnyvale, CA 94089 USA Phone: (408) 744-9040 • Fax: (408) 744-9049 www.thinkSRS.com •e-mail: info@thinkSRS.com Copyright © 1999 All Rights Reserved Revision 1.5 • 11/99 Stanford Research Systems...
Page 2: Table Of Contents
SR830 BASICS PROGRAMMING What is a Lock-in Amplifier? GPIB Communications What Does a Lock-in Measure? RS232 Communications The SR830 Functional Diagram Status Indicators and Queues Reference Channel Command Syntax Phase Sensitive Detectors Interface Ready and Status Time Constants and DC Gain...
Page 3 Table of Contents TESTING CIRCUITRY Introduction Circuit Boards Preset CPU and Power Supply Board Serial Number DSP Logic Board Firmware Revision Analog Input Board Test Record If A Test Fails PARTS LISTS Necessary Equipment DSP Logic Board Front Panel Display Test Analog Input Board 7-15 Keypad Test...
Page 4: Safety And Preparation For Use
LINE CORD LINE VOLTAGE SELECTION The SR830 has a detachable, three-wire power The SR830 operates from a 100V, 120V, 220V, or cord for connection to the power source and to a 240V nominal AC power source having a line fre- protective ground.
Page 6: Specifications
SR830 DSP LOCK-IN AMPLIFIER SPECIFICATIONS SIGNAL CHANNEL Voltage Inputs Single-ended (A) or differential (A-B). Current Input or 10 Volts/Amp. Full Scale Sensitivity 2 nV to 1 V in a 1-2-5-10 sequence (expand off). Input Impedance Voltage: 10 MΩ+25 pF, AC or DC coupled.
Page 7 SR830 DSP Lock-In Amplifier DISPLAYS Channel 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 also be any of these quantities divided by Aux Input 1 or 2.
Page 8 SR830 DSP Lock-In Amplifier COMMAND LIST VARIABLES i,j,k,l,m Integers Frequency (real) x,y,z Real Numbers String REFERENCE and PHASE page description PHAS (?) {x} Set (Query) the Phase Shift to x degrees. FMOD (?) {i} Set (Query) the Reference Source to External (0) or Internal (1).
Page 9 INTERFACE page description 5-19 Reset the unit to its default configurations. IDN? 5-19 Read the SR830 device identification string. LOCL(?) {i} 5-19 Set (Query) the Local/Remote state to LOCAL (0), REMOTE (1), or LOCAL LOCKOUT (2). OVRM (?) {i} 5-19 Set (Query) the GPIB Overide Remote state to Off (0) or On (1).
Page 10 SR830 DSP Lock-In Amplifier STATUS BYTE DEFINITIONS SERIAL POLL STATUS BYTE (5-21) LIA STATUS BYTE (5-23) name usage name usage No data is being acquired RSRV/INPT Set when on RESERVE or INPUT overload No command execution in progress FILTR Set when on FILTR overload...
Page 11 SR830 DSP Lock-In Amplifier 1-10...
Page 12: Getting Started
The sample measurements described in this section are designed to acquaint the first time user with the SR830 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.
Page 13 Getting Started...
Page 14: The Basic Lock-In
The Basic Lock-in THE BASIC LOCK-IN This measurement is designed to use the internal oscillator to explore some of the basic lock-in functions. You will need BNC cables. Specifically, you will measure the amplitude of the Sine Out at various frequencies, sensitivities, time con- stants and phase shifts.
Page 15 The Basic Lock-in The knob is used to adjust parameters which are Use the knob to adjust the phase shift until Y shown in the Reference display, such as phase, is zero and X is equal to the positive amplitude and frequency. The final phase value amplitude.
Page 16 The Basic Lock-in Parameters which have only a few values, such as filter slope, have only a single key which cycles 11. Press the [Slope/Oct] key until 6 dB/oct is through all available options. Press the corre- selected. sponding key until the desired option is indicated by an led.
Page 17 The Basic Lock-in...
Page 18: X, Y, R And Θ
θ X, Y, R and X, Y, R and θ This measurement is designed to use the internal oscillator and an external signal source to explore some of the display types. You will need a synthesized function generator capable of providing a 100 mVrms sine wave at 1.000 kHz (the DS335 from SRS will suffice), BNC cables and a terminator appropriate for the gener- ator function output.
Page 19 θ X, Y, R and should now oscillate at about 0.2 Hz (the accuracy is determined by the crystals of the generator and the lock-in). 4. Press [Channel 1 Display] to select R. The default Channel 1 display is X. Change the display to show R.
Page 20: Outputs, Offsets And Expands
Outputs, Offsets and Expands OUTPUTS, OFFSETS and EXPANDS This measurement is designed to use the internal oscillator to explore some of the basic lock-in outputs. You will need BNC cables and a digital voltmeter (DVM). Specifically, you will measure the amplitude of the Sine Out and provide analog outputs proportional to the measurement.
Page 21 50%. Offsets are useful for making relative measurements. In analog lock-ins, offsets were generally used to remove DC output errors from the lock-in itself. The SR830 has no DC output errors and the offset is not required for most measurements.
Page 22 Outputs, Offsets and Expands turn on the OVLD indicator in the Channel 1 display. 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 displayed values while expand increases the resolution of the display.
Page 23 Outputs, Offsets and Expands 2-12...
Page 24: Storing And Recalling Setups
Storing and Recalling Setups STORING and RECALLING SETUPS The SR830 can store 9 complete instrument setups in non-volatile memory. 1. Turn the lock-in on while holding down the When the power is turned on with the [Setup] key [Setup] key. Wait until the power-on tests are pressed, the lock-in returns to its standard set- completed.
Page 25 Storing and Recalling Setups 2-14...
Page 26: Aux Outputs And Inputs
Aux Outputs and Inputs AUX OUTPUTS and INPUTS This measurement is designed to illustrate the use of the Aux Outputs and Inputs on the rear panel. You will need BNC cables and a digital voltmeter (DVM). Specifically, you will set the Aux Output voltages and measure them with the DVM. These outputs will then be connected to the Aux Inputs to simulate external DC voltages which the lock-in can measure.
Page 27 Aux Outputs and Inputs 6. Press [Channel 2 Display] to select AUX IN 3. Change the Channel 2 display to measure Aux Input 3. 7. Connect Aux Out 1 to Aux In 3 on the rear Channel 2 should now display -5 V (Aux In 3). panel.
Page 28: Sr830 Basics
AND phase. Noise signals at frequencies other The SR830 generates its own sine wave, shown than the reference frequency are rejected and do as the lock-in reference below. The lock-in refer- t + θ...
Page 29 A dual-phase lock-in, such as the SR830, has two PSD's, with reference oscillators 90° apart, and All lock-in measurements can measure X, Y and R directly. In addition, the phase θ...
Page 30: What Does A Lock-In Measure
S(t) = 1.273sin(ωt) + 0.4244sin(3ωt) + 0.2546sin(5ωt) + ... where ω = 2πf. The SR830, locked to f will single out the first component. The measured signal will be 1.273sin(ωt), not the 2V pk-pk that you'd meas- ure on a scope.
Page 31 SR830 Basics...
Page 32: The Sr830 Functional Diagram
Lock-In Amplifier is shown below. The functions in the gray area are handled by the digital signal pro- cessor (DSP). We'll discuss the DSP aspects of the SR830 as they come up in each functional block description. Low Noise 50/60 Hz...
Page 33 SR830 Basics...
Page 34: Reference Channel
Internal Oscillator sine wave. This waveform is sin(ω + 90°). The internal oscillator in the SR830 is basically a 102 kHz function generator with sine and TTL Both reference sine waves are calculated to 20 sync outputs. The oscillator can be phase-locked bits of accuracy and a new point is calculated to the external reference.
Page 35 Noise at nearby frequencies now appears near DC and affects the lock-in output. Phase noise in the SR830 is very low and general- ly causes no problems. In applications requiring no phase jitter, the internal reference mode should be used.
Page 36: Phase Sensitive Detectors
The phase sensitive detectors (PSD's) in the A/D converter used in the SR830 is extremely SR830 act as linear multipliers, that is, they multi- linear, meaning that the presence of large noise ply the signal with a reference sine wave. Analog...
Page 37 SR830 Basics 3-10...
Page 38: Time Constants And Dc Gain
24 dB/oct ponents. This filter is what makes the lock-in such of roll off. Since the filters are digital, the SR830 is a narrow band detector. not limited to just two stages of filtering.
Page 39 This combination of filters numbers and multiplying by the gain. This allows notches all multiples of the reference frequency the SR830 to operate with 100 dB of dynamic and provides overall noise attenuation as well. reserve without any output offset or zero drift.
Page 40: Dc Outputs And Scaling
The two front panel outputs can be configured to output voltages proportional to the CH1 and CH2 The SR830 has the ability to offset the X, Y and R displays or X and Y. outputs. This is useful when measuring deviations in the signal around some nominal value.
Page 41 The X and Y offset and expand functions in the The Ratio indicator below the display is on when- SR830 are output functions, they do NOT affect ever a display is showing a ratio quantity. the calculation of R or θ. R has its own output Display output scaling offset and expand.
Page 42: Dynamic Reserve
SR830 Basics DYNAMIC RESERVE We've mentioned dynamic reserve quite a bit in because the DC output amplifier is running at very the preceding discussions. It's time to clarify high gain and low frequency noise and offset drift dynamic reserve a bit.
Page 43 SR830 run with lower reserve at this sensitivity? To set a scale, the SR830's output noise at 100 dB dynamic reserve is only measurable when the The answer to this question is - Why would you signal input is grounded.
Page 44: Signal Input Amplifier And Filters
For exam- below 60 dB or if the minimum reserve is suffi- ple, suppose the SR830 is set to 5 µV full scale cient, then these filters do not significantly improve 3-17...
Page 45 This filter is transparent to the user. Input Impedance The input impedance of the SR830 is 10 MΩ. If a higher input impedance is desired, then the SR550 remote preamplifier must be used. The SR550 has an input impedance of 100 MΩ...
Page 46: Input Connections
SR830 Basics INPUT CONNECTIONS Differential Voltage Connection (A-B) In order to achieve the best accuracy for a given measurement, care must be taken to minimize the The second method of connection is the differen- various noise sources which can be found in the tial mode.
Page 47 SR830 Basics Current Input (I) AC vs DC Coupling The current input on the SR830 uses the A input The signal input can be either AC or DC coupled. BNC. The current input has a 1 kΩ input impe- The AC coupling high pass filter passes signals dance and a current gain of either 10 above 160 mHz (0.16 Hz) and attenuates signals...
Page 48: Intrinsic (Random) Noise Sources
This can appear as voltage noise when cur- rent is passed through a resistor, or as noise in a Since the input signal amplifier in the SR830 has a current measurement. The shot noise or current bandwidth of approximately 300 kHz, the effective...
Page 49 SR830 Basics quencies more difficult. Other sources of 1/f noise include noise found in vacuum tubes and semiconductors. Total noise All of these noise sources are incoherent. The total random noise is the square root of the sum of the squares of all the incoherent noise sources.
Page 50: External Noise Sources
SR830 Basics EXTERNAL NOISE SOURCES In addition to the intrinsic noise sources discussed For example, if the noise source is a power circuit, in the previously, there are a variety of external then f = 60 Hz and V = 120 V. C...
Page 51 SR830 Basics Microphonics Cures for inductively coupled noise include: Not all sources of noise are electrical in origin. 1) Removing or turning off the interfering Mechanical noise can be translated into electrical noise source. noise by microphonic effects. Physical changes in...
Page 52: Noise Measurements
The averaging time is selected by the same amount of noise as the real filter. SR830 and ranges from 10 to 80 times the time constant. Shorter averaging times yield a very The ENBW is determined by the time constant and poor estimate of the noise (the mean varies rapidly slope as shown below.
Page 53 SR830 Basics 3-26...
Page 54: Power On/Off And Power On Tests
Sine Output Power The power switch is on the rear panel. The SR830 is turned on by push- ing the switch up. The serial number (5 digits) is shown in the CH1 and CH2 displays and the firmware version is shown in the Ref display at power on.
Page 55: Key Click On/Off
Front Panel Knob The knob is used to adjust parameters in the Reference display. The parameters which may be adjusted are internal reference frequency, ref- erence phase shift, sine output amplitude, harmonic detect number, off- sets, Aux Output levels, and various Setup parameters. Local Lockout If the computer interface has placed the unit in the REMOTE state, indi- cated by the REMOTE led, then the keys and the knob are disabled.
Page 56: Keypad Test
Press [Phase] to decrease the number of on LED's until all of the LED's are off. The SR830 is still operating, the output voltages are updated and the unit responds to inter- face commands.
Page 57: Standard Settings
Front Panel STANDARD SETTINGS If the [Setup] key is held down when the power is turned on, the lock-in settings will be set to the defaults shown below rather than the settings that were in effect when the power was last turned off. The default set- tings may also be recalled using the RST command over the computer interface.
Page 58: Signal Input And Filters
Front Panel Signal Input and Filters [Input] The [Input] key selects the front end signal input configuration. The input amplifier can be either a single-ended (A) or differential (A-B) voltage or a current (I). The voltage inputs have a 10 MΩ, 25 pF input impedance. Their connec- tor shields are isolated from the chassis by either 10 Ω...
Page 59 10 Hz or so. If the reference frequency is 70 Hz, do not use the 60 Hz notch filter! The signal will be attenuated and the phase shifted. See the SR830 Basics section for a discussion of when these filters improve a measurement.
Page 60: Sensitivity, Reserve, Time Constants
This key selects the reserve mode, either Low Noise, Normal or High Reserve. The actual reserve (in dB) depends upon the sensitivity. When the reserve is High, the SR830 automatically selects the maximum reserve available at the present full scale sensitivity. When the reserve is Low, the minimum available reserve is selected.
Page 61 It will be very likely that the noise floor of any interfering signal will obscure the signal at the reference and make detection difficult if not impossible. See the SR830 Basics section for more information. Auto Reserve Pressing [AUTO RESERVE] will change the reserve mode to the mini- mum reserve required.
Page 62 Front Panel the detection frequency is below 200 Hz and 100 s is the time constant and the frequency increases above 200 Hz, the time constant WILL change to 30 s. Decreasing the frequency back below 200 Hz will NOT change the time constant back to 100 s.
Page 63 (ENBW) of the low pass filter. This is the measurement bandwidth for X and Y noise and depends upon the time constant and filter slope. (See the Noise discussion in the SR830 Basics section.) FILTER OVLD The OVLD led in the Time Constant section indicates that the low pass filters have overloaded.
Page 64 The synchronous filter does NOT attenuate broadband noise (except at the harmonic frequencies). The low pass filters remove out- puts due to noise and interfering signals. See the SR830 Basics section for a discussion of time constants and filtering.
Page 65: Ch1 Display And Output
The bar graph is ±full scale sensitivity for X, R and X Noise, and ±10V for the Aux Inputs. Ratio displays are shown in % and the bar graph is scaled to ±100%. See the SR830 Basics section for a complete discussion of scaling.
Page 66 If the display is showing a quantity which is affected by an offset or a non-unity expand, then the Offset and Expand indicators are turned on below the display. See the SR830 Basics section for a complete discussion of scaling, off- sets and expands. [Offset On/Off] Pressing this key turns the X or R offset (as selected by the [Display] key) on or off.
Page 67 Front Panel display key ([Phase], [Freq], [Ampl], [Harm #] or [Aux Out]). [Auto Offset] Pressing this key automatically sets the X or R offset percentage to offset the selected output quantity to zero. [Expand] Pressing this key selects the X and R Expand. Use the [Display] key to select either X or R.
Page 68: Ch2 Display And Output
The bar graph is ±full scale sensitivity for Y and Y Noise, ±180 ° for θ, and ±10V for the Aux Inputs. Ratio displays are shown in % and the bar graph is scaled to ±100%. See the SR830 Basics section for a complete discussion of scaling.
Page 69 If the display is showing a quantity which is affected by an offset or a non-unity expand, then the Offset and Expand indicators are turned on below the display. See the SR830 Basics section for a complete discussion of scaling, off- sets and expands. [Offset On/Off] Pressing this key turns the Y offset on or off.
Page 70 Front Panel [Expand] Pressing this key selects the Y Expand. The expand can be 1 (no expand), 10 or 100. If the expand is 10 or 100, the Expand indicator below the display will turn on. The output can never exceed full scale when expanded.
Page 71: Reference
Front Panel Reference [Phase] Pressing this key displays the reference phase shift in the Reference display. The knob may be used to adjust the phase. The phase shift ranges from -180° to +180° with 0.01° resolution. When using an external reference, the reference phase shift is the phase between the external reference and the digital sine wave which is multi- plying the signal in the PSD.
Page 72 When the reference mode is internal, this is the excitation source provid- ed by the SR830. When an external reference is used, this sine output provides a sine wave phase locked to the external reference. The rear panel TTL Output provides a TTL square wave at the reference frequency.
Page 73 102 kHz/N. If an external reference is used and the reference frequency exceeds 102 kHz/N, then N is reset to 1. The SR830 will always track the external reference. Pressing this key displays the harmonic number in the Reference dis- play.
Page 74: Auto Functions
Front Panel Auto Functions Pressing an Auto Function key initiates an auto function which may take some time. The AUTO leds in the CH1 and CH2 displays will be on while the function is in progress. A multi-tone sound will indicate when the auto function is complete and the AUTO leds will turn off.
Page 75 Front Panel all possible input signals. In most cases, the following procedure should setup the SR830 to measure the input signal. 1.Press [AUTO GAIN] to set the sensitivity. 2.Press [AUTO RESERVE]. 3.Adjust the time constant and roll-off until there is no Time Constant overload.
Page 76: Setup
Front Panel Setup [Save] Nine amplifier setups may be stored in non-volatile memory.To save a setup, press [Save] to display the buffer number (1..9) in the CH2 dis- play. Use the knob to select the desired buffer number. Press [Save] again to store the setup in the buffer, or any other key to abort the save process.
Page 77: Interface
Setup. GPIB/RS232 The SR830 only outputs data to one interface at a time. Commands may be received over both interfaces but responses are directed only to the selected interface. Make sure that the selected interface is set correctly before attempting to program the SR830 from a computer.
Page 78 No front panel adjustments may be made. This indicator is on whenever a GPIB Service Request is generated by the SR830. SRQ stays on until a serial poll is completed. ACTIVE This indicator flashes when there is activity on the computer interface.
Page 79: Warning Messages
Front Panel WARNING MESSAGES The SR830 displays various warning messages whenever the operation of the instrument is not obvious. The two tone warning alarm sounds when these messages are displayed. Display Warning Message Meaning LOCL LOut LOCAL LOCKOUT If the computer interface has placed the unit in the REMOTE state, indicated by the REMOTE led, then the keys and the knob are disabled.
Page 80: Rear Panel
The RS232 interface connector is configured as a DCE (transmit on pin 3, receive on pin 2). The baud rate and parity are programmed with the [Setup] key. To connect the SR830 to a PC serial adapter, which is usu- ally a DTE, use a straight thru serial cable.
Page 81: Preamp Connector
Rear Panel These outputs are affected by the X and Y offsets and expands. The actual outputs are X Output = (X/sensitivity - offset)xExpandx10V Y Output = (Y/sensitivity - offset)xExpandx10V where the offset is a percentage of full scale and the expand is an integer from 1, 10 or 100.
Page 82: Using Srs Preamps
9 pin D connectors) from the preamp to the rear panel preamp con- nector on the SR830. Use BNC cables to connect the A output from the preamp to the A input of the SR830. The B output from the preamp (preamp ground) may be connected to the B input of the SR830.
Page 83 Rear Panel 4-30...
Page 84: Status Indicators And Queues
" " are IEEE- 488.2 (1987) defined common commands. These commands also function identically on RS232. The SR830 is configured as a DCE ( transmit on Commands may require one or more parameters. pin 3, receive on pin 2) device and supports CTS/ Multiple parameters are separated by commas (,).
Page 85: Interface Ready And Status
Values returned by the SR830 are sent as a string is finished. Thus a response to the status query in of ASCII characters terminated by a carriage itself signals that the previous command is fin- return <cr>...
Page 86: Detailed Command List
Remote Programming DETAILED COMMAND LIST The four letter mnemonic in each command sequence specifies the command. The rest of the sequence con- sists of parameters. Multiple parameters are separated by commas. Parameters shown in { } are optional or may be queried while those not in { } are required. Commands that may be queried have a question mark in parentheses (?) after the mnemonic.
Page 87: Reference And Phase
Remote Programming REFERENCE and PHASE COMMANDS PHAS (?) {x} The PHAS command sets or queries the reference phase shift. The parameter x is the phase (real number of degrees). The PHAS x com- mand will set the phase shift to x. The value of x will be rounded to 0.01°. The phase may be programmed from -360.00 ≤...
Page 88: Input And Filter
Remote Programming INPUT and FILTER COMMANDS ISRC (?) {i} The ISRC command sets or queries the input configuration. The parame- ter i selects A (i=0), A-B (i=1), I (1 MΩ) (i=2) or I (100 MΩ) (i=3). Changing the current gain does not change the instrument sensitivity. Sensitivities above 10 nA require a current gain of 1 MΩ.
Page 89: Gain And Time Constant
Remote Programming GAIN and TIME CONSTANT COMMANDS SENS (?) {i} The SENS command sets or queries the sensitivity. The parameter i selects a sensitivity below. sensitivity sensitivity 2 nV/fA 50 µV/pA 5 nV/fA 100 µV/pA 10 nV/fA 200 µV/pA 20 nV/fA 500 µV/pA 50 nV/fA 1 mV/nA...
Page 90 Remote Programming SYNC (?) {i} The SYNC command sets or queries the synchronous filter status. The parameter i selects Off (i=0) or synchronous filtering below 200 Hz (i=1). Synchronous filtering is turned on only if the detection frequency (refer- ence x harmonic number) is less than 200 Hz.
Page 91: Display And Output
Remote Programming DISPLAY and OUTPUT COMMANDS DDEF (?) i {, j, k} The DDEF command selects the CH1 and CH2 displays. The parameter i selects CH1 (i=1) or CH2 (i=2) and is required. The DDEF i, j, k com- mand sets display i to parameter j with ratio k as listed below. CH1 (i=1) CH2 (i=2) display...
Page 92: Aux Input And Output
Remote Programming AUX INPUT and OUTPUT COMMANDS OAUX? i The OAUX? command queries the Aux Input values. The parameter i selects an Aux Input (1, 2, 3 or 4) and is required. The Aux Input voltages are returned as ASCII strings with units of Volts. The resolution is 1/3 mV.
Page 93: Setup
OVRM i In general, every GPIB interface command will put the SR830 into the REMOTE state with the front panel deactivated. To defeat this feature, use the OVRM 1 command to overide the GPIB remote. In this mode, the front panel is not locked out when the unit is in the REMOTE state.
Page 94: Auto Functions
Remote Programming AUTO FUNCTIONS AGAN The AGAN command performs the Auto Gain function. This command is the same as pressing the [Auto Gain] key. Auto Gain may take some time if the time constant is long. AGAN does nothing if the time constant is greater than 1 second.
Page 95: Data Storage
Data Storage The SR830 can store up to 16383 points from both the Channel 1 and Channel 2 displays in an internal data buffer. The data buffer is NOT retained when the power is turned off. The data buffer is accessible only via the computer interface.
Page 96 Remote Programming Aliasing Effects In any sampled data stream, it is possible to sample a high frequency signal such that it will appear to be a much lower frequency. This is called aliasing. For example, suppose the lock-in is detecting a signal near 1 Hz with a relatively short time constant. The X output will have a DC component and a 2 Hz component (2xf).
Page 97 Remote Programming PAUS The PAUS command pauses data storage. If storage is already paused or reset then this command is ignored. REST The REST command resets the data buffers. The REST command can be sent at any time - any storage in progress, paused or not, will be reset.
Page 98: Data Transfer
Remote Programming DATA TRANSFER COMMANDS The OUTP? i command reads the value of X, Y, R or θ. The parameter OUTP ? i i selects X (i=1), Y (i=2), R (i=3) or θ (i=4). Values are returned as ASCII floating point numbers with units of Volts or degrees. For example, the response might be "-1.01026".
Page 99 Remote Programming The SNAP? command is a query only command. The SNAP? command is used to record various parameters simultaneously, not to transfer data quickly. OAUX? i The OAUX? command reads the Aux Input values. The parameter i selects an Aux Input (1, 2, 3 or 4) and is required. The Aux Input voltages are returned as ASCII strings with units of Volts.
Page 100 = m x 2 (exp-124) where m is the mantissa and exp is the exponent. The data within the SR830 is stored in this format. Data transfers using this format are faster than IEEE floating point format. If data transfer speed is important, the TRCL? command should be used.
Page 101 At fast sample rates, it is important that the receiving interface be able to keep up. If the SR830 finds that the interface is not ready to receive a point, then the fast transfer mode is turned off.
Page 102: Interface
LOCL (?) {i} The LOCL command sets the local/remote function. If i=0 the SR830 is LOCAL, if i=1 the SR830 will go REMOTE, and if i=2 the SR830 will go into LOCAL LOCKOUT state. The states duplicate the GPIB local/remote states.
Page 103: Status Reporting
Remote Programming STATUS REPORTING COMMANDS The Status Byte definitions follow this section. CLS command clears all status registers. The status enable regis- ters are NOT cleared. ESE (?) {i} {,j} ESE i command sets the standard event enable register to the decimal value i (0-255).
Page 104: Status Byte Definitions
Remote Programming STATUS BYTE DEFINITIONS The SR830 reports on its status by means of four status bytes: the Serial Poll Status byte, the Standard Event Status byte, the LIA Status byte, and the Error Status byte. The status bits are set to 1 when the event or state described in the tables below has occurred or is present.
Page 105: Service Requests
Remote Programming SERVICE REQUESTS (SRQ) A GPIB service request (SRQ) will be generated whenever a bit in both the Serial Poll Status byte AND Serial Poll Enable register is set. Use SRE to set bits in the Serial Poll Enable register. A service request is only generated when an enabled Serial Poll Status bit becomes set (changes from 0 to 1).
Page 106: Lia Status Byte
Remote Programming LIA STATUS BYTE name usage INPUT/RESRV Set when an Input or Amplifier overload is detected. FILTR Set when a Time Constant filter overload is detected. OUTPT Set when an Output overload is detected. UNLK Set when a reference unlock is detected. RANGE Set when the detection frequency switches ranges (harmonic x ref.
Page 107 Remote Programming 5-24...
Page 108 [Setup] key. The default GPIB address is 8; use this address unless a conflict occurs with other instruments in your system. The SR830 will be set to GPIB address 8 whenever a reset is performed (power on with the [Setup] key down).
Page 109 <devName>\n"); exit(1); else initGpib(SR830); txLia("OUTX1"); /* Set the SR830 to output responses to the GPIB port */ setupLia(); /* Setup the SR830 */ printf("\nAcquiring Data\n"); ibtmo(lia,0); /* turn off timeout for lia or set the timeout longer than the scan (10 seconds). The timeout measures the time to transfer the FULL number of bytes, not the time since the most recent byte is received.*/...
Page 110 /* format and print results */ printf ("End of Program"); void printOutBinaryResults(void) /* calculates the first 10 values of R based on the X and Y values taken in FAST mode by the SR830 */ int i; float x,y,r; int *ptr;...
Page 111 Remote Programming void printOutIEEEResults(void) /* prints the first 10 values of R transferred in IEEE floating point format by the SR830 */ int i; printf("\n\n"); for (i=0;i<10;i++) printf("%d %e\n",i,rfBuf[i]); /* this is simple since the values are already IEEE floats */...
Page 112 Remote Programming txLia("SRAT10; SEND0"); /* set 64 Hz sample rate, stop at end */ txLia("DDEF1,1,0; DDEF2,1,0"); /* set CH1=R, CH2=theta. Buffers store CH1 and CH2 */ printf("Scan is Initialized, Press <Enter> to Begin Scan..."); getch(); 5-29...
Page 113 Remote Programming 5-30...
Page 114: Using Sr530 Programs
SR530 application with a minimum of program changes. Of course, some changes will be required and some features are unique to one instrument or the other. For example, SR530 commands can not put the SR830 into a configuration which is not allowed by the SR830. All program routines which query the SR530 status MUST be rewritten to query the equivalent SR830 status using the SR830 status commands.
Page 115 Remote Programming The SR830 does not sense the pre-amplifier. This command is emulat- ed and always returns 0. I {n} Change the remote/local status. The SR830 Override Remote mode can override the I2 command. Use the OVRM command to change this.
Page 116 V {n} Change the value of the SRQ mask. This command changes the serial poll enable register of the SR830. The serial poll byte is that of the SR830 not the SR530! Programs which query the SR530 status need to be changed to query the equivalent SR830 status byte.
Page 117 Remote Programming 5-34...
Page 118: Introduction
Test Record Make a copy of the SR830 Performance Test Record at the end of this section. Fill in the results of the tests on this record. This record will allow you to determine whether the tests pass or fail and also to preserve a record of the tests.
Page 119: Front Panel Display Test
Performance Tests ≤ -55 dBc Spurious TTL SYNC available Recommended SRS DS335 2. AC Calibrator Freq Range 10 Hz to 100 kHz Amplitude 1 mV to 10 V Accuracy 0.1% External phase locking capability Recommended Fluke 5200A 3. DC Voltmeter Range 19.999 V, 4 1/2 digits Accuracy...
Page 120: Self Tests
Performance Tests 1. Self Tests The self tests check the lock-in hardware. These are functional tests and do not relate to the specifications. These tests should be checked before any of the performance tests. Setup No external setup is required for this test. Procedure 1) {PRESET} (Turn on the lock-in with the [Setup] key pressed) Check the results of the DATA, BATT, PROG and DSP tests.
Page 121 Performance Tests...
Page 122: Dc Offset
Performance Tests 2. DC Offset This test measures the DC offset of the input. Setup Connect a 50Ω terminator to the A input. This shorts the input so the lock-in's own DC offset will be measured. Procedure 1) {PRESET} (Turn the lock-in off and on with the [Setup] key pressed) 2) Press the keys in the following sequence: [Freq] Use the knob to set the frequency to 1.00 Hz.
Page 123 Performance Tests...
Page 124: Common Mode Rejection
Performance Tests 3. Common Mode Rejection This test measures the common mode rejection of the lock-in. Setup We will use the internal oscillator sine output to provide the signal. Connect the Sine Out to both the A and B inputs of the lock-in. Use equal length cables from A and B to a BNC TEE.
Page 125 Performance Tests...
Page 126: Amplitude Accuracy And Flatness
Performance Tests 4. Amplitude Accuracy and Flatness This test measures the amplitude accuracy and frequency response. Setup We will use the frequency synthesizer to provide an accurate frequency and the AC calibrator to provide a sine wave with an exact amplitude. Connect the output of the frequency synthesizer to the phase lock input of the calibrator.
Page 127 Performance Tests b) Press [Sensitivity Up/Dn] Select the sensitivity from the table. c) Wait for the R reading to stabilize. Record the value of R for each sensitivity. 4) Frequency response is checked at frequencies above 1 kHz. The test frequencies are listed below. Test Frequencies 24 kHz 48 kHz...
Page 128: Amplitude Linearity
Performance Tests 5. Amplitude Linearity This test measures the amplitude linearity. This tests how accurately the lock-in measures a signal smaller than full scale. Setup We will use the frequency synthesizer to provide an accurate frequency and the AC calibrator to provide a sine wave with an exact amplitude.
Page 129 Performance Tests 6-12...
Page 130: Frequency Accuracy
Performance Tests 6. Frequency Accuracy This test measures the frequency accuracy of the lock-in. This tests the accuracy of the frequency counter inside the unit. The counter is used only in external reference mode. The internal oscillator frequency is set by a crystal and has 25 ppm frequency accuracy.
Page 131 Performance Tests 6-14...
Page 132: Phase Accuracy
Performance Tests 7. Phase Accuracy This test measures the phase accuracy of the lock-in. Due to the design of the lock-in, the phase accuracy can be determined by measuring the phase of the internal oscillator Sine Out. Setup Connect the Sine Out to the A input of the lock-in using a 1 meter BNC cable. Do not use any termination. Procedure 1) {PRESET} (Turn the lock-in off and on with the [Setup] key pressed) 2) Press the keys in the following sequence:...
Page 133 Performance Tests 6-16...
Page 134: Sine Output Amplitude
Performance Tests 8. Sine Output Amplitude Accuracy and Flatness This test measures the amplitude accuracy and frequency response of the internal oscillator Sine Out. Setup We will use the lock-in to measure the Sine Out. Connect the Sine Out to the A input of the lock-in. Procedure 1) {PRESET} (Turn the lock-in off and on with the [Setup] key pressed) 2) Press the keys in the following sequence:...
Page 135 Performance Tests d) Press [Freq] Use the knob to set the internal oscillator frequency to the value in the table. e) Wait for the R reading to stabilize. Record the value of R. f) Repeat steps 4d and 4e for all of the frequencies listed. 5) This completes the sine output amplitude accuracy and frequency response test.
Page 136: Dc Outputs And Inputs
Performance Tests 9. DC Outputs and Inputs This test measures the DC accuracy of the DC outputs and inputs of the lock-in. Setup We will use the digital voltmeter (DVM) to measure the DC outputs of the lock-in. Then we will use one of the outputs to generate a voltage to measure on the DC inputs.
Page 137 Performance Tests c) For each output voltage in the table below, repeat steps 3d and 3e. Output Voltages -10.000 -5.000 0.000 5.000 10.000 d) Use the knob to adjust the Aux Output level to the value from the table. e) Record the DVM reading. 4) Press [Aux Out] Display Aux Out 1 on the Reference display.
Page 138: 10. Input Noise
Performance Tests 10. Input Noise This test measures the lock-in input noise. Setup Connect a 50Ω termination to the A input. This grounds the input so the lock-in's own noise is measured. Procedure 1) {PRESET} (Turn the lock-in off and on with the [Setup] key pressed) 2) Press the keys in the following sequence: [Sensitivity Down] Set the sensitivity to 100 nV.
Page 139 Performance Tests 6-22...
Page 140: Performance Test Record
Page 1 of 4 SR830 Performance Test Record Serial Number Tested By Firmware Revision Date Equipment Used 1. Self Tests Test Pass Fail DATA ____ ____ BATT ____ ____ PROG ____ ____ ____ ____ 2. DC Offset Input Coupling Reading...
Page 141 Page 2 of 4 SR830 Performance Test Record 5. Amplitude Linearity Sensitivity Calibrator Ampl. Lower Limit Reading Upper Limit 1.0000 Vrms 0.9900 V _______ 1.0100 V 100.00 mVrms 0.0990 V _______ 0.1010 V 10.000 mVrms 0.0098 V _______ 0.0102 V 6.
Page 142 Page 3 of 4 SR830 Performance Test Record 9. DC Outputs and Inputs (continued) Output Offset Lower Limit Reading Upper Limit -100.00 9.980 V _______ 10.020 V -50.00 4.980 V _______ 5.020 V 0.00 -0.010 V _______ 0.010 V 50.00 -5.020 V...
Page 143 Page 4 of 4 SR830 Performance Test Record 9. DC Outputs and Inputs (continued) Input Voltage Lower Limit Reading Upper Limit AUX IN 1 -10.000 -10.040 V _______ -9.960 V -5.000 -5.030 V _______ -4.970 V 0.000 -0.020 V _______ 0.020 V...
Page 144: Circuit Boards
Display Board Keypad Board CIRCUIT BOARDS CAUTION The SR830 has five main printed circuit boards. Always disconnect the power cord and The five boards shown contain most of the active wait at least one minute before open- circuitry of the unit. The rear panel circuit board ing the unit.
Page 145 Circuit Description...
Page 146 Circuit Description CPU and POWER SUPPLY BOARD The CPU board contains the microprocessor SPIN KNOB system. All display, front panel, disk, and comput- er interfaces are on this board. The knob is an optical encoder buffered by U612. Each transition of its outputs is clocked into U610 MICROPROCESSOR SYSTEM or U611 and generates an interrupt at the output of U602A.
Page 147 Circuit Description POWER SUPPLY The 24 VDC brushless fan cools the heat sink and CAUTION: Dangerous voltages are present on power supply rectifiers. this circuit board whenever the instrument is attached to an AC power source and the rear panel power switch is "on". Always disconnect the power cord and wait at least one minute before opening the unit.
Page 148 30 MHz clock. This keeps the VCO DSP PROCESSOR within range at all frequencies. The SR830 utilizes a Motorola 24-bit DSP56001 TIMING GENERATOR digital signal processor (U501). The DSP is config- ured without external memory. The lock-in algo-...
Page 149 Circuit Description transmit port each cycle. The transmit port oper- ±22V from the power supply is used to generate ates at twice the frequency of the receive port. The ±15V for the op amps. ±5.6V for analog switches DSP writes to the other channel of each DAC via a and op amps is generated from the ±15V supplies.
Page 150 The design of the are attenuated by at least 96 dB. This is accom- front end input amplifier in the SR830 was driven plished with an 8-zero 9-pole elliptical low pass by an effort to provide optimum performance in the filter.
Page 151 Circuit Description a rate of 256 kHz. One channel is dedicated to the input signal. The other channel reads one of the Aux A/D inputs. The Aux inputs are multiplexed so that each input is read every four cycles. The two digital output streams are buffered by U406 and sent to the DSP board.
Page 152 Parts List PARTS LIST DSP Logic Board Parts List Ref No. SRS Part No. Value Component Description C 101 5-00060-512 1.0U Cap, Stacked Metal Film 50V 5% -40/+85c C 114 5-00100-517 2.2U Capacitor, Tantalum, 35V, 20%, Rad C 117 5-00100-517 2.2U Capacitor, Tantalum, 35V, 20%, Rad C 119...
Page 153 Parts List C 283 5-00100-517 2.2U Capacitor, Tantalum, 35V, 20%, Rad C 290 5-00023-529 Cap, Monolythic Ceramic, 50V, 20%, Z5U C 301 5-00002-501 100P Capacitor, Ceramic Disc, 50V, 10%, SL C 302 5-00002-501 100P Capacitor, Ceramic Disc, 50V, 10%, SL C 303 5-00002-501 100P...
Page 154 Parts List C 603 5-00038-509 Capacitor, Electrolytic, 50V, 20%, Rad C 604 5-00239-562 680P Cap., NPO Monolitic Ceramic, 50v, 5% Ra C 610 5-00002-501 100P Capacitor, Ceramic Disc, 50V, 10%, SL C 611 5-00002-501 100P Capacitor, Ceramic Disc, 50V, 10%, SL C 630 5-00033-520 Capacitor, Electrolytic, 16V, 20%, Rad...
Page 155 Parts List 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 N 602 4-00334-425 10KX5 Resistor Network SIP 1/4W 2% (Common) N 603 4-00463-421 82X4 Res. Network, SIP, 1/4W,2% (Isolated) N 604 4-00463-421 82X4 Res.
Page 156 Parts List R 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%, 50PPM R 222 4-00188-407 4.99K Resistor, Metal Film, 1/8W, 1%, 50PPM R 226 4-00782-448 54.9 Resistor, Metal Film, 1W, 1%, R 227 4-00193-407 Resistor, Metal Film, 1/8W, 1%, 50PPM...
Page 157 Parts List TP203 1-00143-101 TEST JACK Vertical Test Jack TP204 1-00143-101 TEST JACK Vertical Test Jack TP301 1-00143-101 TEST JACK Vertical Test Jack TP302 1-00143-101 TEST JACK Vertical Test Jack TP303 1-00143-101 TEST JACK Vertical Test Jack TP304 1-00143-101 TEST JACK Vertical Test Jack TP401 1-00143-101...
Page 158 Parts List U 606 3-00499-343 SR850 U606 GAL/PAL, I.C. U 608 3-00411-340 74HC273 Integrated Circuit (Thru-hole Pkg) U 609 3-00411-340 74HC273 Integrated Circuit (Thru-hole Pkg) U 610 3-00387-340 74HC245 Integrated Circuit (Thru-hole Pkg) U 611 3-00440-340 74HC573 Integrated Circuit (Thru-hole Pkg) U 612 3-00440-340 74HC573...
Page 159 Parts List 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 1000P Capacitor, Monolythic Ceramic, COG, 1% C 382 5-00148-545 1000P Capacitor, Monolythic Ceramic, COG, 1% C 386 5-00013-501 Capacitor, Ceramic Disc, 50V, 10%, SL C 390...
Page 160 Parts List K 103 3-00444-335 HS-211-5 Relay K 104 3-00196-335 HS-212S-5 Relay K 105 3-00444-335 HS-211-5 Relay L 501 6-00006-602 Inductor, Radial N 101 4-00560-421 47KX3 Res. Network, SIP, 1/4W,2% (Isolated) N 102 4-00244-421 10KX4 Res. Network, SIP, 1/4W,2% (Isolated) N 103 4-00497-421 1.5KX4...
Page 161 Parts List 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 R 208 4-00556-407 2.94K Resistor, Metal Film, 1/8W, 1%, 50PPM R 221 4-00595-407 13.3K Resistor, Metal Film, 1/8W, 1%, 50PPM R 222 4-00663-407 Resistor, Metal Film, 1/8W, 1%, 50PPM...
Page 162 Parts List R 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, 1%, 50PPM R 374 4-00158-407 2.00K Resistor, Metal Film, 1/8W, 1%, 50PPM R 375 4-00158-407 2.00K Resistor, Metal Film, 1/8W, 1%, 50PPM R 379 4-00303-407 7.87K...
Page 163 Parts List TP407 1-00143-101 TEST JACK Vertical Test Jack TP408 1-00143-101 TEST JACK Vertical Test Jack TP501 1-00143-101 TEST JACK Vertical Test Jack TP502 1-00143-101 TEST JACK Vertical Test Jack TP503 1-00143-101 TEST JACK Vertical Test Jack TP504 1-00143-101 TEST JACK Vertical Test Jack TP505 1-00143-101...
Page 164 Parts List 0-00043-011 4-40 KEP Nut, Kep 0-00187-021 4-40X1/4PP Screw, Panhead Phillips 0-00243-003 TO-220 Insulators 0-00373-000 CARD EJECTOR Hardware, Misc. 1-00087-131 2 PIN JUMPER Connector, Female CPU and Power Supply Parts List Ref No. SRS Part No. Value Component Description BT701 6-00001-612 BR-2/3A 2PIN PC...
Page 165 Parts List C 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 C 1019 5-00225-548 .1U AXIAL Capacitor, Ceramic, 50V,+80/-20% Z5U AX C 1021 5-00225-548 .1U AXIAL Capacitor, Ceramic, 50V,+80/-20% Z5U AX C 1022 5-00225-548 .1U AXIAL...
Page 166 Parts List 7-00512-701 SR810/830 CPU Printed Circuit Board 3-00021-325 2N3904 Transistor, TO-92 Package 3-00021-325 2N3904 Transistor, TO-92 Package Q 401 3-00026-325 2N5210 Transistor, TO-92 Package Q 701 3-00022-325 2N3906 Transistor, TO-92 Package Q 702 3-00021-325 2N3904 Transistor, TO-92 Package Q 705 3-00022-325 2N3906 Transistor, TO-92 Package...
Page 167 Screw, Panhead Phillips 1-00087-131 2 PIN JUMPER Connector, Female 5-00262-548 .01U AXIAL Capacitor, Ceramic, 50V,+80/-20% Z5U AX 7-00501-720 SR830-8 Fabricated Part Front Panel Display Board Parts List Ref No. SRS Part No. Value Component Description 3-00546-340 HDSP-4830 Integrated Circuit (Thru-hole Pkg)
Page 168 Parts List C 10 5-00219-529 .01U Cap, Monolythic Ceramic, 50V, 20%, Z5U C 11 5-00219-529 .01U Cap, Monolythic Ceramic, 50V, 20%, Z5U C 12 5-00219-529 .01U Cap, Monolythic Ceramic, 50V, 20%, Z5U C 13 5-00219-529 .01U Cap, Monolythic Ceramic, 50V, 20%, Z5U C 14 5-00219-529 .01U...
Page 169 Parts List D 31 3-00547-310 RED COATED LED, Coated Rectangular D 32 3-00547-310 RED COATED LED, Coated Rectangular D 33 3-00547-310 RED COATED LED, Coated Rectangular D 34 3-00547-310 RED COATED LED, Coated Rectangular D 35 3-00547-310 RED COATED LED, Coated Rectangular D 36 3-00547-310 RED COATED...
Page 170 Parts List D 88 3-00575-311 GREEN MINI LED, Subminiature D 89 3-00575-311 GREEN MINI LED, Subminiature D 90 3-00575-311 GREEN MINI LED, Subminiature D 91 3-00575-311 GREEN MINI LED, Subminiature D 92 3-00575-311 GREEN MINI LED, Subminiature D 93 3-00575-311 GREEN MINI LED, Subminiature D 94...
Page 171 Res. Network, SIP, 1/4W,2% (Isolated) N 13 4-00263-425 1.0KX7 Resistor Network SIP 1/4W 2% (Common) 7-00492-701 SR830 DISPLAY Printed Circuit Board 7-00493-701 SR830 KPD BD Printed Circuit Board 7-00437-701 FFT/DSP LI Printed Circuit Board 7-00513-701 SR810/830 AB IN Printed Circuit Board 7-00514-701...
Page 172 Parts List 0-00089-033 4” 0-00097-040 #6 FLAT Washer, Flat 0-00100-040 1/4X1/16 Washer, Flat 0-00104-043 #4 NYLON Washer, nylon 0-00108-054 1” #26 Wire #26 UL1061 0-00122-053 2-1/4” #24 Wire #24 UL1007 Strip 1/4x1/4 Tin 0-00125-050 3” #18 Wire #18 UL1007 Stripped 3/8x3/8 No Tin 0-00126-053 3-1/2”...
Page 173 Parts List 6-00212-630 1”X.25”CYL Ferrite Beads 6-00214-630 .5”X.25”CYL Ferrite Beads 7-00124-720 TRANSCOVER2-MOD Fabricated Part 7-00406-720 SR770-12 Fabricated Part 7-00497-740 SR830-1 Keypad, Conductive Rubber 7-00499-735 SR830-4/-5 Injection Molded Plastic 7-00500-709 SR830 Lexan Overlay 7-00502-721 SR830-9 Machined Part 7-00505-720 SR830-12 Fabricated Part...
Page 174 Parts List 7-31...

SRS Labs SR830 Manual

General Information

Getting Started

Sr830 Basics

Operation

Front Panel

Rear Panel

Using SRS Preamps

Detailed Command List

Status Byte Definitions

Using Sr530 Programs

Performance Tests

Performance Test Record

Quick Links

Need help?

Questions and answers

Related Manuals for SRS Labs SR830

Summary of Contents for SRS Labs SR830

Table of Contents