Model 331 Autotuning Temperature Controller - Advanced Research Systems - #1

Intelligently designed and well-integrated for high performance and ease of use, the Model 331 Temperature Controllers are suitable for most cryogenic and many higher temperature measurement and control applications. The Model 331 Temperature Controllers combine the easy operation and unsurpassed reliability of the Model 330 with improved sensor input and interface flexibility, including compatibility with negative temperature coefficient (NTC) RTDs. Backed by Lake Shore's tradition of excellence in cryogenic sensors and instrumentation, the Model 331 Temperature Controllers set the standard for mid-price range temperature control instruments.

The Model 331 Temperature Controllers are available in two versions. The Model 331S is fully equipped for interface and control flexibility. The Model 331E shares measurement and display capability with the Model 331S, but does not include the IEEE-488 interface, relays, analog voltage output, or a second control loop. The purchaser's choice of Model 331S or 331E must be specified at time of order and cannot be reconfigured in the field.

The Model 331 Temperature Controllers are designed for high performance with sensors across the 1.4 to over 1000 K temperature range and in difficult sensing conditions, including magnetic fields. The Model 331 Temperature Controllers feature two inputs, with a high-resolution 24-bit analog-to-digital converter and separate current source for each input. Sensors are optically isolated from other instrument functions for quiet and repeatable sensor measurements. Sensor data from each input can be read up to ten times per second, with display updates twice each second.

Standard temperature response curves for silicon diodes, platinum RTDs, and many thermocouples are included. Up to twenty 200-point CalCurves^TM for Lake Shore calibrated sensors or user curves can be loaded into non-volatile memory via computer interface or the instrument front panel. A built-in SoftCal^TM algorithm can also be used to generate curves for silicon diodes and platinum RTDs, for storage as user curves.

The Model 331E offers one and Model 331S two proportional-integral-derivative (PID) control loops. A PID control algorithm calculates control output based on temperature setpoint and feedback from the control sensor. Wide tuning parameters accommodate most cryogenic cooling systems and many small high temperature ovens. Control output is generated by a high-resolution digital-to-analog converter for

smooth continuous control. The first control loop drives heater output. Both versions also include manual control mode.

Heater output for the Models 331S and 331E is a well-regulated variable DC current source. Heater output is optically isolated from other circuits to reduce interference and ground loops. Heater output can provide up to 50 W of continuous power as resistive heater load and includes two lower ranges for systems with less cooling power. Heater output is short circuit protected to prevent instrument damage if the heater load is accidentally shorted.

The setpoint ramp feature allows smooth continuous changes in setpoint and can also make the approach to a setpoint temperature more predictable. The zone feature can automatically change control parameter values for operation over a large temperature range; values for ten different temperature zones can be loaded into the instrument, which will select the next appropriate value on setpoint change.

Model 331E is equipped with a serial RS-232C interface, while Model 331S includes serial RS-232C and parallel IEEE-488 interfaces. Maximum reading rate can be achieved with either interface. The most frequently used functions can be accomplished from the instrument front panel with one or two keystrokes. Nearly every function on the instrument front panel can also be performed via computer interface. Both versions include Model 330 command emulation mode for drop-in interchangeability with Model 330 temperature controllers in existing systems.

High and low alarms for each input can be used in latching mode, requiring user intervention before alarms reset. For the Model 331S, alarms can also be used in conjunction with relays in non-latching mode, where alarms automatically reset when the activation condition ends, to perform simple on-off control functions. Relay assignments are configurable so that one relay may be assigned to each input or both assigned to a single input for high/low control.

The Model 331S's analog voltage output can be configured to send a voltage proportional to temperature to a strip chart recorder or data acquisition system. The user may select the scale and data sent to the output, including temperature, sensor units, or linear equation results. Under manual control, the analog voltage output can also serve as a voltage source for any other application.