Open-frame PID controllers cut installation costs

Edited by the Engineeringtalk editorial team Jan 31, 2003

Available from Audon Electronics is a novel range of low-cost open-frame temperature/process controllers.

Available from Audon Electronics is a novel range of low-cost open-frame temperature/process controllers.

There are several controllers in the range for use with either traditional AC loads or with DC Peltier-type heat engines.

All controllers feature serial communication ports, PID control, alarms, built-in solid-state-relay output and easy-to-use programming software.

Once programmed, these controllers can operate in stand-alone mode or can form part of a larger Scada system.

These controllers make for a lower cost alternative to traditional panel-mount controllers, and their onboard SSRs reduce installation costs.

The model 5C7-461 is a 250V AC 15A output temperature controller that accepts type J, K, or S thermocouples or a +/-100mV process input.

The controller consists of a printed circuit card mounted to an integral heat sink/mounting bracket that is DIN compatible and may be mounted either horizontally or vertically.

Connections are via screw and spade terminals.

The 5C7-461 controller is configured through a RS485 communications port using the Windows setup program.

Once the controller is configured, the PC may be disconnected and the controller can be left to operate as a stand-alone unit.

The software allows the operator to select the applicable thermocouple type and scaling, set PID tuning parameters, set control limits, configure alarms, give the controller an identifying name, select either heating or cooling mode, plus select and enable a protective password.

Controller tuning parameters consist of proportional bandwidth (P), integral gain (I), and the derivative rate (D) for selecting P, PI, PD, or PID operation.

An on/off operating mode with an adjustable hysteresis may also be selected.

Alarm selections consist of no alarm function, a fixed high and/or low temperature alarm or tracking alarms.

These alarms can be selected for either latching or nonlatching operation and drives an alarm relay output.

Alarm reset is accomplished either via the PC communications interface or an optional local switch.

The Windows software also permits the monitoring of actual temperature, set temperature, percent of power applied to the load, and alarm status in.

It allows selection of the set temperature, turning the power on or off, cancelling an alarm condition, tuning the controller settings and displaying the current sensor selection.

The models 5C7-250/251 are similar controllers but have RS232 communication ports and are designed for use with thermistors.

The models 5C7-361/362 are designed to provide bidirectional control of Peltier-type thermoelectric heat engines for both cooling and heating applications.

The controllers' H-bridge MOSFET output drive configuration allows for bidirectional flow of current through the thermoelectric modules with a capacity up to 25A.