Thermocouple is a commonly used temperature measurement instrument in temperature measurement components. It directly measures the temperature, and transfer the temperature signal into a thermoelectromotive force signal, through the electrical instrument (secondary instrument) into the measured medium temperature. The various thermocouples are often very different in appearance, but their basic structures are generally the same. They are usually made up of the main parts of the thermal electrode, insulation sheathing tube and junction box. They are usually used in conjunction with display instruments, recording instruments and electronic adjustment supporting the use of equipment.