The utility model relates to a temperature sensing element, which is a primary instrument. The closed circuit composed of 2 different components of the conductor, due to different materials, different electron density to produce electron diffusion, stable equilibrium after the potential. When the ends of the gradient temperature, the loop current will produce, produce thermal electromotive force, temperature difference is greater, the greater the current. After the thermal electromotive force measured can know the temperature value. A thermocouple is actually an energy converter that converts heat energy into electrical energy.

Technical advantages: thermocouple thermocouple temperature range, stable performance; high - precision measurement, thermocouple in direct contact with the measured object, is not affected by the medium heat; fast response time, thermocouple temperature change of flexible response; measuring range, thermocouple from the continuous measurement of -40 + 1600 C can be reliable; thermocouple, mechanical good strength. Long service life, convenient device.

Couple must be by two kind of different but with certain requirements of the conductor (or semiconductor) material to form a loop. There is a temperature difference between the thermocouple measuring end and the reference end.

Two different materials of the conductor or semiconductor A and B welded together to form a closed loop. When there is a temperature difference between two and of the conductor A and B, the electromotive force is generated between the two, so it is a kind of electric current in the circuit. Thermocouples are working with this effect.