6ES7331-7PF11-0AB0 Siemens TC module wiring question

[p17061]

Hello,

We have a project in which we will use the 6ES7331-7PF11-0AB0 TC module for measuring temperature. We use K type thermocouples normally. Our electrician has drawn the system with the K type thermocouples connections in a junction box and then the wiring leaving the junction box to the PLC 6ES7331-7PF11-0AB0 module is normal LIYCY 8x0,34 cable that is not thermocouple cable. He then has the PT100 external compensation thermometer connected in the same junction box and from the junction box to the 6ES7331-7PF11-0AB0 module is normal LIYCY 8x0,34 cable. I am wondering how this will work if the K type thermocouples are connected in the junction box and the wiring back to the module is of different materials than the thermocouple? Is it so that when using a PT100 external compensation thermometer, the channels measure the voltage and it does not matter that the wires connected to the module are of different materials than the thermocouples? We will use "external compensation" in the module configuration.

Thanks for your help!

Pete

 

[daba]

It is in the junction box where you will be creating "Cold-Junctions", i.e. junctions between your "K" thermocouple metals, and your copper wires.

These dissimilar metal junctions will generate their own voltages, which must be accounted for to get a proper reading of the "Hot" junction, i.e. the thermocouple itself.

Mounting the PT100 sensor in the junction box is exactly the way to compensate for the thermocouple effects of the connections in it.