Analog card for Thermocouple

I had a question about thermocouples and analog card. I have a 1762-if20f2 and i am useing the outputs to control a vfd and i am trying to use the inputs to read a thermocouple. I have 6 heaters i am using on a blow molding machine 4 of the thermocouples are wired to a 1762-IT4 thermocouple card and 3 of the 4 are working the 4th i think is just a bad thermocouple. The other 2 thermocouples i have hooked up to a 1762-IF20f2. I dont know if i it setup wrong or it just wont work with thermocouples. Could someone give me some direction on how to use the analog card with a thermocouple. I know i should just buy another thermocouple card but if i could get the IF20f2 to work that would be better. Thank you.

A thermocouple produces a millivolt signal, your 1762-IF2OF2 requires a 0 to 10vdc or 4-20mA singal. The simplest way to make the two devices work together would be to use a signal conditioner matched to your type thermocouple.

There are many different types of signal conditioners or temperature transmitters that could be recommended.

I normally prefer to use a standard analog input with thermocouples and add the signal conditioners. Standard analog inputs are less expensive and more readily available. Using 4-20mA is much more noise immune. But, in your case since you already have the 1762-IT4 card in your system, if there is room to add another one, that might be the cleaner solution.

Welcome to PLCTalk!

Check the setup file for the -IT4 card. Each of the inputs can be set for different type thermocouples.

It could be on channel is programmed for K type and the others T, or similar.

Also, the wire all the way from the thermocouple to the PLC input terminals has to be the same type thermocouple wire, and if run through terminal strips there may be a problem if the metal in the terminal itself is the wrong type.

Spectrum Controls makes some really nice 1762 hardware as well as for other platforms.

Thanks for all of the advice. I ended up ordering another thermocouple card from ***********. Again thank you for the input.