I have a controller with two k-type thermocouple inputs. I'd like to have one of those inputs be the difference between the two TCs. Since TCs are voltage devices, it looks like an opamp would be perfect here. Maybe three: one for each TC, then one to compare the two signals and send the difference to the TC input. I've just never cared about microvolt levels before. Would this work?
The temperature ranges I will be measuring will be from 20C to 200C, they will never be negative.
I also need to have one TC still connected to the controller, so the circuit diagram below won't work for me, I don't think.
The controller is Japanese from 1997 and has no manual. It has K-type inputs.