SRS Labs manual SR530 Guide to Programming, Communicating with the SR530, Command Syntax

Page 23

SR530 Guide to

Programming

The SR530 Lock-in Amplifier is remotely programmable via both RS232 and GPIB interfaces. It may be used with laboratory computers or simply with a terminal. All front panel features (except signal input selection and power) may be controlled and read via the computer interfaces. The SR530 can also read the analog outputs of other laboratory instruments using its four general purpose analog input ports. There are also two programmable analog output ports available to provide general purpose control voltages.

Communicating with the SR530

Before using either the RS232 or GPIB interface, the appropriate configuration switches need to be set. There are two banks of 8 switches, SW1 and SW2, located on the rear panel. SW1 sets the GPIB address and SW2 sets the RS232 parameters. The configuration switches are read continuously and any changes will be effective immediately. For details on switch settings, see page 7 at the front of this manual.

Command Syntax

Communications with the SR530 use ASCII characters. Commands to the SR530 may be in either UPPER or lower case.

A command to the SR530 consists of one or two command letters, arguments or parameters if necessary, and an ASCII carriage return (<cr>) or line-feed (<lf>) or both. The different parts of the command do not need to be separated by spaces. If spaces are included, they will be ignored. If more than one parameter is required by a command, the parameters must be separated by a comma. Examples of commands are:

G 5 <cr>

set the sensitivity to 200 nV

T 1,4 <cr>

set the pre filter to 30 mS

F <cr>

read the reference frequency

P 45.10 <cr>

set phase shift to 45.10¡

X 5,-1.23E-1 <cr>

set port X5 to -0.123 V

Multiple commands may be sent on a single line. The commands must be separated by a semicolon

(;)character. The commands will not be executed until the terminating carriage return is sent.

An example of a multiple command is:

G 5; T 1,4; P 45.10 <cr>

It is not necessary to wait between commands. The SR530 has a command input buffer of 256 characters and processes the commands in the order received. Likewise, the SR530 has an output buffer (for each interface) of 256 characters.

In general, if a command is sent without parameters, it is interpreted as a request to read the status of the associated function or setting. Values returned by the SR530 are sent as a string of ASCII characters terminated usually by carriage return, line-feed. For example, after the above command is sent, the following read commands would generate the responses shown below.

Command

Response from the SR530

G <cr>

5<cr><lf>

T 1 <cr>

4<cr><lf>

P <cr>

45.10<cr><lf>

The choice of terminating characters sent by the SR530 is determined by which interface is being used and whether the 'echo' feature is in use. The terminating sequence for the GPIB interface is always <cr><lf> (with EOI). The default sequence for RS232 is <cr> when the echo mode is off, and <cr><lf> when the echo mode is on. The terminating sequence for the RS232 interface may be changed using the J command.

Note that the terminating characters are sent with each value returned by the SR530. Thus, the response to the command string G;T1;P<cr> while using the RS232 non-echo mode would be 5<cr>4<cr>45.10<cr>.

Front Panel Status LED's

The ACT LED flashes whenever the SR530 is sending or receiving characters over the computer interfaces.

The ERR LED flashes whenever an error has occurred, such as, an illegal command has been received, a parameter is out of range, or a communication buffer has exceeded 240 characters. This LED flashes for about three seconds on power-up if the battery voltage is insufficient to retain previous instrument settings.

19

Page 22 Page 24
Image 23
Page 22 Page 24
Contents Model SR530 Page Table of Contents Appendix C Gpib NON-OPERATING OperatingPage SR530 Specification Summary Gpib DemodulatorFront Panel Summary Enbw Abridged Command List Status Byte Definition Configuration SwitchesSensitivity Signal InputsSignal Filters SR510 Guide to Operation Front PanelChannel 1 Display Dynamic ReserveStatus Display SelectOffset Channel OutputOutput Channel Rel ChannelChannel 2 Display Expand ChannelRcosø Output Auto Phase Trigger Level Rsinø OutputReference Input Time Constant Reference ModePhase Controls Reference DisplayLocal and Remote PowerDefaults SR530 Guide to Operation Rear Panel Page Front Panel Status LEDs Command SyntaxSR530 Guide to Programming Communicating with the SR530Try-Out with an Ascii Terminal RS232 Echo and No Echo OperationLOW Norm High SR530 Command ListN1,n2,n3,n4 Page Bit ErrorsStatus Byte Common Software Problems include ResetTrouble-Shooting Interface Problems Common Hardware Problems includeSR530 with the Gpib Interface SR530 with the RS232 InterfaceSR530 with Both Interfaces Serial Polls and Service RequestsGpib with RS232 Echo Mode Measurement Example Lock-in TechniqueShielding and Ground Loops Understanding the SpecificationsPage Page SR530 Block Diagram DC Amplifiers and System Gain Signal ChannelPhase Sensitive Detectors Reference ChannelCircuit Description Demodulator and Low Pass Amplifier Reference OscillatorMicroprocessor Control Analog Output and ControlExpand Front PanelGpib Interface Power SuppliesRS232 Interface Calibration and Repair Multiplier AdjustmentsAmplifier and Filter Adjustments Replacing the Front-End Transistors Notch FiltersNon-Essential Noise Sources Appendix a Noise Sources and CuresPage Page Case 2 RS232 with Control Lines Case 1 The Simplest ConfigurationAppendix B Introduction to the RS232 Baud RateFinal Tip Stop BitsParity Voltage LevelsBus Description Appendix C Introduction to the GpibProgram Example IBM PC, Basic, via RS232 Appendix D Program ExamplesProgram Example IBM PC, Microsoft Fortran v3.3, via RS232 Page #include stdio.h Program Example IBM PC, Microsoft C v3.0, via RS232Page Program Example 4 IBM PC,Microsoft Basic, via Gpib ′INCREMENT X6 Output by 2.5 MV Program Example HP85 via Gpib Documentation Dpdt Oscillator Board Parts ListPC1 SW1BT1 Main Board Parts ListBR1 BR2SR530 Component Parts List SR530 Component Parts List CX1 22U MINPIN D Gpib ShieldedMPSA18 CY1FU1 SR530 Component Parts List SR530 Component Parts List SR530 Component Parts List SR530 Component Parts List SR530 Component Parts List SR513 Assy SPSTX84PDT SR530 Component Parts List Static RAM, I.C Z80A-CPU#4 Flat TIE AnchorTranscover MicaFront Panel Board Parts List RED LD3 LD1LD2 Quad Board Parts List SR530 Component Parts List PC1 SR530 Component Parts List Miscellaneous Parts List SR530 Component Parts List

SR530, Lock-In Amplifier specifications

The SRS Labs Lock-In Amplifier, model SR530, is a powerful tool designed for high-precision measurements in the realm of scientific research and industrial applications. This state-of-the-art instrument excels in extracting small signals from noisy environments, making it an invaluable asset for experiments in fields such as physics, engineering, and materials science.

One of the main features of the SR530 is its ability to perform synchronous detection, which is key to improving signal-to-noise ratios. By utilizing a reference signal, the device correlates the incoming signal with the reference to effectively filter out noise, allowing for the accurate measurement of weak signals that might otherwise be obscured. This process of phase-sensitive detection is fundamental to the operation of the Lock-In Amplifier.

The SR530 offers a wide frequency range, covering from 0.1 Hz to 100 kHz. This broad frequency response allows it to handle a diverse array of signals, making it suitable for various applications including optical detection, capacitance measurements, and in many cases, voltammetry. The device is also equipped with multiple inputs and outputs, facilitating the integration with other laboratory equipment and enabling complex experimental setups.

Precision is further enhanced with its adjustable time constant, which allows users to optimize the response time based on experimental needs. The user can choose time constants from 10 microseconds to 10 seconds, accommodating fast dynamic measurements as well as those requiring stability over longer durations.

Another remarkable characteristic of the SR530 is its digital processing capabilities. The device features a highly accurate digital voltage measurement system, minimizing drift and ensuring long-term stability. Additionally, the use of microprocessors enhances data handling and allows for features such as programmable settings, facilitating automated measurements.

Moreover, the SR530 includes a range of output options, including analog outputs, which can be used for direct signal processing, as well as digital interfaces for integration with computers. This ensures that users can not only capture high-fidelity data but also analyze and display it efficiently.

In conclusion, the SRS Labs SR530 Lock-In Amplifier stands out due to its sophisticated technology, versatile features, and robust performance. Its precision, flexibility, and ease of use make it an ideal choice for researchers and engineers looking to unlock the potential of weak signal measurement in complex environments.
Top Page Image Contents