Temperature Controller, TEC and Heater

What is the final control element, i.e. how does the controller know whether to operate the heating device or the cooling device?

A block of aluminum is being cooled/heated, and a RTD or Thermocouple will be placed on a surface of these block and the reading from this sensor will be compared to the setpoint in the controller to determine which device is necessary.

Many single loop PID controllers can handle heat-cool applications, driving a heater when the PV temperature is below setpoint and driving the cooling element when the PV temperature is above the setpoint. There's usually some form of deadband adjustment to avoid running both simultaneously.

Every single loop PID controller I've come across can be configured to run On-Off, as an alternative to proportional control. Modulating the cycle time of an binary control element is typically called time proportional or pulse width modulation, depending on the device's heritage.

I don't know what a TEC is. Are you talking about a Peltier style cooler?

Regardless, can this TEC be driven in an on-off mode by supplying a voltage/current source and then turning it off?

Or does it requires some varying voltage to drive it? If so, can your model supply that output voltage range for whatever the impedance of the TEC is?

If so, then it's likely to be workable.

A thermoelectric cooler (TEC) is an another name for a Peltier Cooler.

For this application, I believe I will require two separate control loops because the heater and the TEC have different responses. Furthermore, for the TEC output, I would like PI or PID control, but the output of the control loop as a duty cycle, so full power would be an 100% duty cycle, and the duty cycle would decrease as the temperature sensor read closer to the setpoint. Since the heater will most likely be powered by alternating current, something similar to go to a relay connected to 120 V AC.

Thank you very much. I will looking over the manual for the UDC2500.

While this is a relatively small application compared to what the controller may be expecting, the devices are low powered, I will keep you auto-tune warning in mind.

A standard thermostat for a heating cooling unit set on automatic

will do all that you ask

The performance requirement was clearly stated:

>where there are temperature setpoints from 0 C to 180 C

>an RTD or Thermocouple will be placed on a surface of this block

How does one get either of these typical residential/commercial automatic heat/cooling thermostats to

a) cover the stated range of 0-180°C?

b) remotely sense the surface temperature at the target temperature range, given their construction with internal temperature sensors?

I do not know how tight of a dead band you need, or the mass of the item that you are testing. I do a lot of work at the local university dealing with environmental chambers, incubators and other lab equipment, where temperature control is critical.

As stated above there are many PLC,s out there that will give you dual control, and may be suitable for your need.

The following may not be for you, but it is another method of tight temperature control. Most environmental chambers and incubators will run the cooling cycle solid, using pulsed re-heat to trim the temperature to the set point. This works well between -20 and +35 deg C. Above that I rely on a PLC with a PID.

If you wish to pulse the heat, than a SCR driven by the controller would be best to handle any load.