SRS Labs Lock-In Amplifier, SR530 manual Calibration and Repair, Multiplier Adjustments

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Calibration and Repair

This section details calibration of the instrument. Calibration should be done only by a qualified electronics technician.

********* WARNING *********

The calibration procedure requires adjusting the instrument with power applied and so there is a risk of personal injury or death by electric shock. Please be careful.

Most of the calibration parameters are determined by a computer aided calibration procedure after burn-in at the factory. These calibration parameters are quite stable and so will not need to be adjusted. Calibration parameters which may need field adjustment are detailed below.

Multiplier Adjustments

On the HIGH dynamic reserve setting, there can be some reference frequency feedthrough. This section describes how to null this unwanted output.

This adjustment requires an oscilloscope and a signal generator which can provide a 500Hz reference signal.

Allow the unit to warm up for about 1 hour.

Reset the unit by turning it off and back on while holding the LOCAL key down.

Select voltage input A and connect a 50 1/2 terminator or shorting plug to the A input BNC connector. Connect the 500 Hz reference signal to the reference input. Set the SENSITIVITY to 1mV and the DYN RES to HIGH. The PRE TIME CONSTANT should be set to 1mS and the POST TIME CONSTANT to NONE. Connect the scope to the CHANNEL 1 OUTPUT on the front panel. Set the scope to 2V/div and 5mS/div. Externally trigger the scope using the reference input signal.

After about 90 seconds, the scope display should show a 500 Hz sine wave on a 30 Hz (500/16 Hz) square wave. Remove the four screws holding the top panel on. Slide the top panel back about half way. Using a small screwdriver, adjust P402 at location D2 to

minimize the 500 Hz output. Adjust P403 at location C2 to minimize the 30 Hz output.

Now set the both time constants to 1S. Adjust P404 at location F4 to zero the output. This adjustment has a range of 20% of full scale on the HIGH dynamic reserve setting. (2% on NORM and 0.2% on LOW). This zeroes the DC output of Channel 1 on all dynamic reserve ranges.

Now connect the scope to the CHANNEL 2 OUTPUT. Set the PRE TIME CONSTANT to 1mS and the POST TIME CONSTANT to NONE. Adjust P1102 to minimize the 500 Hz output. Adjust P1103 to minimize the 30 Hz output. Set both time constants to 1S. Adjust P1104 to zero the output. All three potentiometers are located on the plug-in board in the center of the main circuit board.

Replace the top panel.

Amplifier and Filter Adjustments

This section describes how to adjust the Common Mode Rejection and Line notch filter frequencies. An oscilloscope and a signal generator which can provide an accurate line frequency and twice line frequency sine wave are required.

Allow the unit to warm up for about 1 hour.

Reset the unit by turning it off and back on while holding the LOCAL key down.

Remove the four screws holding down the top panel. Slide the panel back about halfway.

CMRR

Set the reference frequency to 100 Hz. It is convenient to use the SYNC output of the signal generator as the reference input if it is available. Connect the sine output of the signal generator to the A input and set the input selector to A. With the SENSITIVITY at 100mV, adjust the amplitude of the input signal to 100 mV (full scale).

Now set the input selector to A-Band connect the signal to both the A and B inputs. Set the SENSITIVITY to 20µV, the DYN RES to NORM and the BANDPASS filter IN. Connect the scope to the SIGNAL MONITOR output on the rear panel. Set the scope to AC coupled, 0.2V/div, and 10mS/div. Externally trigger the scope using the reference input signal.

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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 DefinitionSR510 Guide to Operation Front Panel Signal InputsSignal Filters SensitivityDisplay Select Dynamic ReserveStatus Channel 1 DisplayRel Channel OutputOutput Channel Offset ChannelExpand Channel Rcosø OutputChannel 2 Display Auto Phase Rsinø Output Reference InputTrigger Level Reference Display Reference ModePhase Controls Time ConstantPower DefaultsLocal and Remote SR530 Guide to Operation Rear Panel Page Communicating with the SR530 Command SyntaxSR530 Guide to Programming 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 Common Hardware Problems include ResetTrouble-Shooting Interface Problems 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 Reference Channel Signal ChannelPhase Sensitive Detectors DC Amplifiers and System GainCircuit Description Reference Oscillator Demodulator and Low Pass AmplifierFront Panel Analog Output and ControlExpand 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 Baud Rate Case 1 The Simplest ConfigurationAppendix B Introduction to the RS232 Case 2 RS232 with Control LinesVoltage Levels Stop BitsParity 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 SW1 Oscillator Board Parts ListPC1 DpdtBR2 Main Board Parts ListBR1 BT1SR530 Component Parts List SR530 Component Parts List Gpib Shielded 22U MINPIN D 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.CMica TIE AnchorTranscover #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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