When is composed of two different conductors or semiconductor a circuit, the mutual connection at both ends. As long as the temperature of the two nodes is different, such as the end temperature of t, called end or hot end work, on the other side temperature is to is called the free end, circuit will generate an electromotive force. The direction and size of the electromotive force is related to the conductor material and the temperature of the two contact, this phenomenon is called 'thermoelectric effect', the electromotive force is called 'thermoelectric emfs. In the process of application of thermocouple thermoelectric potential problems need attention has the following three 1, thermocouple thermoelectric potential is the difference on both ends of the thermocouple temperature function, rather than a function of temperature difference on both ends of the thermocouple; 2, the size of the thermocouple thermoelectric potential produced by, when material is uniform thermocouple, has nothing to do with the length and diameter of thermocouple, and only at the ends of the thermocouple material composition and temperature difference; 3, when the two thermocouple wire thermocouple material composition is determined, the size of the thermocouple thermoelectric potential, only related with the thermocouple temperature difference; If the thermocouple cold end temperature keeping, this into the thermocouple thermoelectric potential is only the end of the single value function of temperature. Two different welding material a conductor or semi-conductor a and b, form a closed loop. When two conductor temperature difference between two persistent points 1 and 2, occurs between the electromotive force, thus forming the size of a current in the circuit, this kind of phenomenon called the thermoelectric effect. Thermocouple is in using this effect to work. When is composed of two different conductors or semiconductor a circuit, the mutual connection at both ends. As long as the temperature of the two nodes is different, such as the end temperature of t, called end or hot end work, on the other side temperature is to is called the free end, circuit will generate an electromotive force. The direction and size of the electromotive force is related to the conductor material and the temperature of the two contact, this phenomenon is called 'thermoelectric effect', the electromotive force is called 'thermoelectric emfs.