Model TC-24-25 RS232 Temperature Controller

APPLICATION
TheTC-24-25 RS232 is a bi-directional control for independent thermoelectric coolers or in conjunction with auxiliary or supplemental resistive heaters for both cooling and heating applications. The "H" bridge configuration of the solid state MOSFET output devices allows for the bi-directional flow of current through the thermoelectric coolers. Highly efficient N-channel output devices are used for this control mode.

This controller is PC programmable via an RS232 communication port for direct interface with a compatible PC. The RS232 communications interface has 1500 VAC isolation from all other electronic circuitry minimizing interference from noise or errant signals caused by common ground loops. The easily accessible communications link permits a variety of operational mode configurations. Field selectable parameters or data acquisition in a half duplex mode can be performed. This controller will accept a communications cable length in accordance with RS232 interface specifications. The supplied software is compatible with Windows 95/98 and Windows NT.

Once the desired set parameters are established, the PC may be disconnected and the TC-24-25 RS232 becomes a unique, stand alone controller. All parameter settings are retained in non-volatile memory.

The user friendly, communications software requires no prior programming experience to establish operation. A command set is provided for qualified personnel to program a software interface or use as an embedded control.

Mechanically, the control printed circuit board is mounted to a metal bracket that is suitable for either horizontal or vertical orientation. Input and output connections are accessible via screw type terminal strips, fast-on terminals, and a 0.100 center connector.

TECHNICAL DESCRIPTION
The TC-24-25 RS232 is capable of operating from an input supply voltage of 12 through 28 VDC, common to many available thermoelectric coolers. The self-contained MOSFET output devices deliver load currents from 0.1 to 25 amperes (NOTE: consult appropriate installation instructions for power supply and heat sinking requirements for high current operation). This unit will control total load power up to 680 watts with a finite temperature resolution of 0.05°C.

The output signal to the thermoelectric cooler is Pulse Width Modulated and is PC selectable for either 675 Hz or 2700 Hz operation. Pulse Width Modulation averages the amount of energy provided to the module and reduces the extreme temperature excursions that are experienced with an "on/off" system. This tends to extend the life and reliability of the thermoelectric devices. The PWM control scheme affords control accuracy to within ±0.05°C. at the control sensor.

The controller tuning structure allows designation of a variety of control features. The computer set value provides for manual control of the output, either polarity, from 0% to 100% of load power. Proportional bandwidth (P) in degrees, integral reset (I) in repeats per minute, and the derivative rate (D) in minutes may be configured for P, PI, PD, or PID control. In addition, a deadband control (on/off) with an adjustable hysteresis may be selected. Differential temperature control is offered when two input sensing thermistors are chosen.

A control temperature range of -20°C. to 100°C is standard when using TE Technology's standard thermistor sensor probe for the PC's primary set temperature. Additional external set temperature input types may be selected. They include a remote set temperature potentiometer, a 0 to 5 VDC signal, and a 0 to 20 ma current loop. These secondary inputs are used to define and "map" the secondary input to an adjustable temperature range. Differential set temperature control may also be selected from this configuration menu. All temperatures may be consistently displayed in °C or °F.

Differential control is accomplished by selecting the primary set temperature with the second thermistor input and establishing the offset with the computer set temperature. The unit will control the differential between Input 2 (reference temperature) and Input 1 (actual system temperature).

Two types of control output modes may be selected. This determines the direction of the current flow through the thermoelectric cooler during the heat cycle. This current flow may be from Wire Point WP1 ( ) to Wire Point WP2 (-). Alternatively, this current flow may be reversed from WP2 ( ) to WP1 (-) as selected in the configuration menu.

Several alarm types may be selected which provide a 5 VDC output, rated for 25 ma of current. They consist of no alarm function, tracking alarm, and fixed value alarm. Alarm set temperature values are entered in the setup menu. The computer-controlled selection is available for additional embedded controller input/output options. The alarm setup menu also provides for selection of an alarm latching condition. The alarm sensor may be either the control temperature sensor or a secondary thermistor sensor.

The various alarms have the ability to determine the status of the output power to the thermoelectric cooler or auxiliary heater. Power may be maintained during an alarm condition or the main power may be shut down.

The TC-24-25 RS232 comes with one MP-2379 thermistor. If you would like to purchase additional thermistors, please indicate when ordering.

SPECIFICATIONS

• Input voltage from 12 to 28 VDC
• Self-contained, 0.1 to 25 A load rating
• PC programmable via RS232 communications port
• Bi-directional control for heating and cooling applications
• Solid state "H" bridge operation
• Control temperature of -20ºC to 100ºC
• Proportional (P), Integral (I) and Derivative (D) control that can be selected as P, PI, PD or PID; or on/off with an adjustable hysteresis
• Temperature resolution of 0.05ºC
• Pulse width modulation of output
• Selectable modulation frequency of 675 Hz or 2700 Hz
• Control stability of ±0.05ºC
• 1500 VAC isolated RS232 communications interface
• Controls up to 680 W
• Set temperature selectable
• PC set with controller stand alone operation
• Remote user set temperature potentiometer
• 4 to 20 MA current loop
• 0V to 5V adjustable range
• Differential temperature control
• No computer programming experience required to use the communications software program
• Command set is provided so programmers may create their own software interface or embedded controller applications
• PC configurable alarms for 5VDC at 25MA
• Alarm cancel: selectable via PC or remote contacts
• Non-volatile memory retention of parameters