Hi guys, I'm working on a project which includes monitoring the temperature of 90gallon tank and controlling it with a PID. I just have a quick question, for me to be able to extend the length of the thermocouple, can I use just simple copper wire toward the female plug (coming from the PID) or do I have to use the same thermocouple wire?
I believe that the junction at which the two wire meet is where the magic happens, so it wouldn't matter what I use as an extension? Am I right?
You can connect any wire for that. The heat detection properties of a thermocouple is found at the junction of the two different metals. Everything else is just to carry voltage that the junction produces due to The Seebeck effect.
You have to be careful here. In some cases you have to use cable with the same makeup as the thermocouple, and in others you can use what is called compensating cable. If you don't, you are just creating another thermocouple connection (metals of dissimlar type), creating another thermocouple junction. Every time you make a connection of unlike metals, you create a new junction, and you start getting an average or spurious readings of all the junctions. I would suggest you look deeper & contact an instrument manufacturing company for further info. Many of them would have applications manuals etc.. Also you may find further info from component suppliers with temperature controllers in their catalogues.
Hmmm.. I hadn't thought of that.
Correct me if I'm wrong, but If the compensating cable and the wire from the Thermocouple are properly insulated and are not subjected to the temperature being measured, there shouldn't be any problem right?