PID module mounts on control platform

Paul Boughton

TTI (Thurlby Thandar Instruments) is introducing the SIM960 analogue PID controller as the latest addition to the SRS SIM (Small Instrumentation Modules) family.

SIM is described as a robust, versatile platform in which up to eight high-performance instruments share the same compact mainframe and computer interface. Unlike some other modular systems, both front-panel and computer operation is possible. SIM provides the functionality that users need while avoiding the cost of unnecessary features. Users can configure their own systems from a broad and growing selection of modules.

The SIM960 analogue PID controller combines analogue signal handling with digital control, giving the user the best of both worlds. High-bandwidth (100kHz) control loops may be implemented without discrete time or quantisation artefacts.

Furthermore, the low-noise front end brings better performance to noise-sensitive applications such as laser power and wavelength stabilisation, cryogenics and scanning probe microscopy. User-settable gain of up to 1000 times gives greater flexibility, thereby reducing the need for input pre-amplification. The unit can be used together with the SIM921 AC resistance bridge to provide a flexible and cost-effective temperature control system.

An internal ramp generator can control voltage slew rate between predefined start and stop setpoints. The output is clamped within upper and lower user limits to guard against system overload. Conditional integration electronics provide anti-windup on the integrating capacitors, leading to faster recovery from saturation conditions.

The amplified error signal (P x e) and the output may be monitored with an LED bar display or via the millivolt-resolution numeric display. The 'setpoint' and 'measure' input signals can also be monitored on the numeric display.

Front-panel control enables easy adjustment of system parameters and convenient monitoring of input and output signals. Power and serial communication are via a 15-pin D-sub connector that mates with the SIM900 mainframe. All instrument parameters can be set and queried via the serial interface.

SIM960 analogue PID controller

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