It is a thermosensitive element, a primary instrument.ThermocoupleDirect temperature measurement. A closed loop composed of conductors made from two different materials, due to the difference in materials, different electronic densities result in electron diffusion, which, upon stabilization and equilibrium, generates an electric potential. When there is a temperature gradient between the two ends, an electric current is produced in the loop, creating a thermoelectric potential. The greater the temperature difference, the stronger the current. After measuring the thermoelectric potential, the temperature value can be known.