SRS Labs SR530, Lock-In Amplifier manual

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Capacitive Coupling. A voltage on a nearby piece of apparatus (or operator) can couple to a detector via a stray capacitance. Although Cstray may be very small, the coupled in noise may still be larger than a weak experimental signal.

Capacitive Noise Coupling

To estimate the noise current through Cstray into the detector we have

i= Cstray dV = jwCstrayVnoise dt

where a reasonable approximation to Cstray can be made by treating it as parallel plate capacitor. Here, w is the radian frequency of the noise source (perhaps 2 * π * 60Hz ), Vnoise is the noise voltage source amplitude (perhaps 120 VAC). For an area of A = (.01 m)2 and a distance of d = 0.1m, the 'capacitor' will have a value of 0.009 pF and the resulting noise current will be 400pA. This meager current is about 4000 times larger than the most sensitive current scale that is available on the SR510 lock-in.

Cures for capacitive coupling of noise signals include:

1)removing or turning off the interfering noise source,

2)measuring voltages with low impedance sources and measuring currents with high impedance sources to reduce the effect of istray,

3)installing capacitive shielding by placing both the experiment and the detector in a metal box.

Inductive Coupling. Here noise couples to the experiment via a magnetic field:

Inductive Noise Coupling

A changing current in a nearby circuit gives rise to a changing magnetic field which induces an emf in the loop connecting the detector to the experiment.

(emf = dØ B/dt.) This is like a transformer, with the experiment-detector loop as the secondary winding.)

Cures for inductively coupled noise include:

1)removing or turning off the interfering noise source (difficult to do if the noise is a broadcast station),

2)reduce the area of the pick-up loop by using twisted pairs or coaxial cables, or even twisting the 2 coaxial cables used in differential hook-ups,

3)using magnetic shielding to prevent the magnetic field from inducing an emf (at high frequencies a simple metal enclosure is adequate),

4)measuring currents, not voltages, from high impedance experiments.

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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 SwitchesSignal Filters Signal InputsSR510 Guide to Operation Front Panel SensitivityStatus Dynamic ReserveDisplay Select Channel 1 DisplayOutput Channel OutputRel Channel Offset ChannelExpand Channel Rcosø OutputChannel 2 Display Auto Phase Rsinø Output Reference InputTrigger Level Phase Controls Reference ModeReference Display Time ConstantPower DefaultsLocal and Remote SR530 Guide to Operation Rear Panel Page SR530 Guide to Programming Command SyntaxCommunicating with the SR530 Front Panel Status LEDsTry-Out with an Ascii Terminal RS232 Echo and No Echo OperationLOW Norm High SR530 Command ListN1,n2,n3,n4 Page Errors Status ByteBit Trouble-Shooting Interface Problems ResetCommon Hardware Problems include Common Software Problems includeSR530 with the Gpib Interface SR530 with the RS232 InterfaceSerial Polls and Service Requests Gpib with RS232 Echo ModeSR530 with Both Interfaces Measurement Example Lock-in TechniqueShielding and Ground Loops Understanding the SpecificationsPage Page SR530 Block Diagram Phase Sensitive Detectors Signal ChannelReference Channel DC Amplifiers and System GainCircuit Description Demodulator and Low Pass Amplifier Reference OscillatorExpand Analog Output and ControlFront Panel Microprocessor ControlPower Supplies RS232 InterfaceGpib Interface Multiplier Adjustments Amplifier and Filter AdjustmentsCalibration and Repair Replacing the Front-End Transistors Notch FiltersNon-Essential Noise Sources Appendix a Noise Sources and CuresPage Page Appendix B Introduction to the RS232 Case 1 The Simplest ConfigurationBaud Rate Case 2 RS232 with Control LinesParity Stop BitsVoltage Levels Final TipBus 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 PC1 Oscillator Board Parts ListSW1 DpdtBR1 Main Board Parts ListBR2 BT1SR530 Component Parts List SR530 Component Parts List PIN D 22U MINGpib 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 Static RAM, I.C Z80A-CPUTranscover TIE AnchorMica #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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