A thermocouple is a temperature-sensing element and a primary instrument that directly measures temperature. It consists of a closed circuit composed of two conductors of different materials. Due to the difference in materials, different electron densities cause electron diffusion, and an electric potential is generated after reaching a stable equilibrium. When there is a temperature gradient between the two ends, a current is generated in the circuit, producing a thermoelectric potential. The larger the temperature difference, the larger the current. The temperature value can be determined after measuring the thermoelectric potential. A thermocouple is essentially an energy converter that converts thermal energy into electrical energy.
Technical advantages of thermocouples: Thermocouples have a wide temperature measurement range and relatively stable performance; high measurement accuracy, as the thermocouple is in direct contact with the object being measured and is not affected by the intermediate medium; fast thermal response time, as thermocouples respond quickly to temperature changes; large measurement range, thermocouples can continuously measure temperatures from -40 to +1600℃; reliable performance and good mechanical strength. They have a long service life and are easy to install.
A thermocouple must consist of a closed circuit made of two conductors (or semiconductors) of different properties but meeting certain requirements. There must be a temperature difference between the measuring end and the reference end of the thermocouple.
Two conductors or semiconductors A and B of different materials are welded together to form a closed circuit. When there is a temperature difference between the two junctions 1 and 2 of conductors A and B, an electromotive force is generated between them, thus forming a current in the circuit. This phenomenon is called the thermoelectric effect. Thermocouples work by utilizing this effect.
