SRS Labs Lock-In Amplifier manual RS232 Echo and No Echo Operation, Try-Out with an Ascii Terminal

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The REM LED is on whenever the SR530 is programmed to be in the remote state.

RS232 Echo and No Echo

Operation

In order to allow the SR530 to be operated from a terminal, an echo feature has been included which causes the unit to echo back commands received over the RS232 port. This feature is enabled by setting switch 6 on SW2 to the DOWN position. In this mode, the SR530 will send line-feeds in addition to carriage returns with each value returned and will also send the prompts 'OK>' and '?>' to indicate that the previous command line was either processed or contained an error. Operating the SR530 from a terminal is an ideal way to learn the commands and responses before attempting to program a computer to control the SR530. When the unit is controlled by a computer, the echo feature should be turned off to prevent the sending of spurious characters which the computer is not expecting.

Try-Out with an ASCII Terminal

Before attempting any detailed programming with the SR530, it is best to try out the commands using a terminal. Connect a terminal with an RS232 port to the RS232 connector on the rear panel of the SR530. A 'straight' RS232 cable is required since the SR530 is a DCE and the terminal is a DTE. Set the baud rate, parity, and stop bits to match the terminal by setting SW2 per the switch setting table given on page 7. The echo mode should be enabled (switch 6 DOWN). After setting SW2 and connecting the terminal, hold down the LOCAL key while turning the unit on. This causes the SR530 to assume its default settings so that the following discussion will agree with the actual responses of the SR530. The ACT and ERR LED's on the front panel will flash for a second and the sign-on message will appear on the terminal. Following the message, the prompt 'OK>' will be displayed. This indicates that the SR530 is ready to accept commands.

Type the letter 'P' followed by a carriage return (P<cr>). The SR530 responds by sending to the terminal the characters 0.00 indicating that the phase is set to 0 degrees. In general, a command with no arguments or parameters reads a setting of the unit. To set the phase to 45 degrees, type the command, P45<cr>. To see that the phase did change, use the SELECT key on the front panel to display the phase on the REFERENCE

DIGITAL DISPLAY. Typing the phase read command, P<cr>, will now return the string 45.00 to the terminal.

Now read the gain using the sensitivity read command, G<cr>. The response should be 24 meaning that the sensitivity is at the 24th setting or 500 mV. Change the sensitivity by typing G19<cr>. The sensitivity should now be 10 mV. Check the front panel to make sure this is so.

The Channel 1 Output of the lock-in is read by typing the command, Q1<cr>. The response is a signed floating point number with up to 5 significant digits plus a signed exponent. Change the gain to 10 uV using the G10 command. The response to the Q1 command will now be similar to the previous one except that the exponent is different.

Attach a DC voltmeter to the X6 output on the rear panel. The range should allow for 10V readings. The voltage at the X6 output can be set using the X6 command. Type X6,5.0<cr> and the X6 output will change to 5.0V. To read this back to the terminal, just type X6<cr>. When setting the X6 voltage, the voltage may be sent as an integer (5), real (5.000), or floating point (0.500E1) number. Now connect the X6 output to the X1 input (also on the rear panel). X1 through X4 are analog input ports. To read the voltage on X1, simply type X1<cr>. The response 5.000 should appear on the terminal. The analog ports X1 through X6 can be used by your computer to read outputs of other instruments as well as to control other laboratory parameters.

At this point, the user should experiment with a few of the commands. A detailed command list follows.

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Contents Model SR530 Page Table of Contents Appendix C Gpib Operating NON-OPERATINGPage SR530 Specification Summary Demodulator GpibFront Panel Summary Enbw Abridged Command List Configuration Switches Status Byte DefinitionSignal Inputs Signal FiltersSR510 Guide to Operation Front Panel SensitivityDynamic Reserve StatusDisplay Select Channel 1 DisplayOutput Output ChannelRel Channel Offset ChannelExpand Channel Rcosø OutputChannel 2 Display Auto Phase Rsinø Output Reference InputTrigger Level Reference Mode Phase ControlsReference Display Time ConstantPower DefaultsLocal and Remote SR530 Guide to Operation Rear Panel Page Command Syntax SR530 Guide to ProgrammingCommunicating with the SR530 Front Panel Status LEDsRS232 Echo and No Echo Operation Try-Out with an Ascii TerminalSR530 Command List LOW Norm HighN1,n2,n3,n4 Page Errors Status ByteBit Reset Trouble-Shooting Interface ProblemsCommon Hardware Problems include Common Software Problems includeSR530 with the RS232 Interface SR530 with the Gpib InterfaceSerial Polls and Service Requests Gpib with RS232 Echo ModeSR530 with Both Interfaces Lock-in Technique Measurement ExampleUnderstanding the Specifications Shielding and Ground LoopsPage Page SR530 Block Diagram Signal Channel Phase Sensitive DetectorsReference Channel DC Amplifiers and System GainCircuit Description Reference Oscillator Demodulator and Low Pass AmplifierAnalog Output and Control ExpandFront Panel Microprocessor ControlPower Supplies RS232 InterfaceGpib Interface Multiplier Adjustments Amplifier and Filter AdjustmentsCalibration and Repair Notch Filters Replacing the Front-End TransistorsAppendix a Noise Sources and Cures Non-Essential Noise SourcesPage Page Case 1 The Simplest Configuration Appendix B Introduction to the RS232Baud Rate Case 2 RS232 with Control LinesStop Bits ParityVoltage Levels Final TipAppendix C Introduction to the Gpib Bus DescriptionAppendix D Program Examples Program Example IBM PC, Basic, via RS232Program Example IBM PC, Microsoft Fortran v3.3, via RS232 Page Program Example IBM PC, Microsoft C v3.0, via RS232 #include stdio.hPage Program Example 4 IBM PC,Microsoft Basic, via Gpib ′INCREMENT X6 Output by 2.5 MV Program Example HP85 via Gpib Documentation Oscillator Board Parts List PC1SW1 DpdtMain Board Parts List BR1BR2 BT1SR530 Component Parts List SR530 Component Parts List 22U MIN PIN DGpib Shielded CX1CY1 FU1MPSA18 SR530 Component Parts List SR530 Component Parts List SR530 Component Parts List SR530 Component Parts List SR530 Component Parts List SPSTX8 4PDTSR513 Assy SR530 Component Parts List Z80A-CPU Static RAM, I.CTIE Anchor TranscoverMica #4 FlatFront Panel Board Parts List RED LD1 LD2LD3 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.
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