How Thermocouples Work

Thermocouple is a temperature device. Its main features are wide temperature measurement range and stable temperature measurement performance. At the same time, it has a simple structure, good dynamic response, and can transmit electrical signals remotely, which is convenient and centralized control. The temperature measurement principle of thermocouple is based on connecting two different conductors or semiconductors into a closed loop. When the temperatures at the two junctions are different, a thermoelectric potential will be generated in the loop. This phenomenon is called, also known as. The thermoelectric potential generated in a closed loop consists of two potentials, "thermoelectric potential" and "contact potential". Thermoelectric potential refers to the potential generated by the two ends of the same conductor due to different temperatures. Different conductors have different electron densities, so the potential they generate is also different. Contact potential refers to the potential formed when two different conductors are in contact because their electron densities are different, so a certain amount of electron diffusion occurs. The size of the contact potential depends on the material properties of the two different conductors and the temperature of their contact points.

At present, the thermocouples used internationally have a standard specification. The international regulations stipulate that thermocouples are divided into eight different scales, namely B, R, S, K, N, E, J and T. The lowest measurable temperature is minus 270 degrees Celsius and the highest is 1800 degrees Celsius. Among them, B, R, and S belong to the platinum series of thermocouples. Since platinum is a precious metal, they are also called precious metal thermocouples, and the remaining ones are called cheap metal thermocouples.