Thermocouple is a commonly used temperature measuring component in temperature measuring instruments. It directly measures the temperature and converts the temperature signal into a thermoelectric potential signal, which is converted into the temperature of the measured medium by an electric meter (secondary meter). The shape of various thermocouples is often very different due to needs, but their basic structure is roughly the same, usually composed of hot electrode, insulating sleeve, protection tube, junction box and etc., and often equip with display instrument, recording instrument and electronic regulator, like multiplex temperature meter, black test corner and etc.

According to the seeback effect, when two different metals are connected together, there is a contact voltage between the two contact points, which depends on the temperature. The connection of thermocouple materials is standard, and the different properties of the thermocouple materials determine their different applications.

The technical advantages of thermocouple: 1). thermocouple temperature measurement range is wide, performance is stable; 2). measurement accuracy is high, thermocouple is in direct contact with the object to be tested, and is not affected by intermediate medium; 3). thermal response time is fast, and thermocouple has flexible response to temperature change; 4). The measuring range is large, and the thermocouple can be continuously measured from -40 to + 1600 °C; 5). the thermocouple has reliable performance and good mechanical strength. 6). The service life is long and the device is convenient.