small plc with a thermacouple input


Thread Starter


We are looking for a small plc similar to a Siemens s7-221 (cheapy!) but with a thermacouple input. We usually use temperature controllers
for our heaters but I would rather do it via touchscreen control.

Thank you all
You could use an Allen Bradley Micrologix PLC with a Thermocouple input and use their Panelview 550 Touchscreen communicating on DH485 Protocol
I have been using the IDEC series PLC. They have several models and a fairly decent software platform. It is worth having a look at, they are about half the price of an Allen Bradley.

Zan Von Flue

Does this mean you want to network the controllers?

S7-200 EM231 is a 4 input module for thermoelements used with CPUs 222, 224 and 226.

At work I have (per oven group), a central PLC (S7-315-2 DP) with a touch screen and 20 ovens( with FM355C). Because it's a Profibus CPU, it's also possible to use the a DP-thermalelement input(for example from Wago or Beckoff) mounted close to the oven, and use the internal loop controller in the CPU, this would be cheaper. I haven't found how many internal controllers are allowed to be called up. Set and actual temperature values can be directly controlled. Not small - touchscreen - network - reliable.
just a thought

Steve Myres, PE

The approach that I've seen for this issue is to use an analog to frequency converter into a high speed count input on the PLC. Calex 8500 or 8600 series should do what you want.

The other approach would be ot find a small PLC with analog input. The DL05 series from Automation Direct has an add-in module available for analog. PLC plus module is around $200, I think, but you'll also need a thermocouple to DC
analog transmitter.
I agree with the IDECs IZUMI choice. They are very compact and cheap. You can also choose from several models and they support almost every kind of thermocouple inputs.

Don Clutterbuck

I would look at the Horner OCS product. It is an Plc/Operator interface built in one unit.
You can add a thermocouple card. The Ocs also has built in Auto tuning PID loops. goto