KNOWLEDGEBASE

What is a thermocouple (TC) and how does it work?

A thermocouple (TC) is a temperature sensor. It reads the temperature in the kiln and gives the information to the DynaTrol or pyrometer. A TC is made from 2 different metals. Type K TCs are alumel (-) and chromel (+). Alumel is magnetic, chromel is not. Also, when examined closely, alumel is a bit more copper colored and chromel is a bit more silvery. Type S TCs are Platinum and Platinum with 10% Rodium. Once the two metals are welded together, a small millivoltage is actually generated from the welded joint. This millivoltage changes degree by degree as the kiln gets hotter/ colder. The millivoltage can be sensed by the DynaTrol or by a pyrometer, and each different amount of millivoltage is assigned to a different temperature. The DynaTrol can translate the millivoltage signal into a recognizable temperature. Because the signal is in millivolts any point of resistance in the circuit will change the millivolt value and the corresponding displayed temp reading. Old TC wires, a poor connection, or overheated/ pinched TC wires are the most common ways to have an inaccurate TC reading. Because there is more than one TC in the kiln it becomes difficult for the controller to even out the different temps when one of them is not reading accurately. E- 1 and the elements seem fine is the result when this happens.