Thermocouple as the temperature measurement based on the principle of, temperature-sensing component in thermoelectric phenomena of the seebeck discovered is 1821. I. e. , when the two different conductor or semiconductor into a closed loop, if they are the ends of the junction temperature is different, it creates an electric current in the circuit, the electromotive force in this shows that the circuits. This physical phenomenon called the thermoelectric effect or the seebeck effect, the corresponding temperature difference electromotive force is called the seebeck potential, thermoelectric potential for short. K type thermocouple under 0 ℃ temperature can be measured, if is Ⅲ K type thermocouple, the lower measurable - Temperature of 200 ℃. K type thermocouple and other working principle of thermocouple, same type K thermocouple is positive, nickel-chromium alloy of nickel and silicon alloy anode welded together at the end of the two conductors. The welding end of the two conductors called K type thermocouple thermal electrode, the weld end for the hot end, the welding end of the cold end. In temperature measurement, the measured object medium, insert the thermocouple to the hot side to feel the temperature of the measured medium, the cold end under constant temperature, electric measuring instrument is connected by wires. Due to the thermocouple at both ends of the temperature is different, can produce thermoelectric potential in the thermocouple circuit, in the case of the thermocouple cold junction temperature unchanged, produced by the thermocouple thermoelectric potential changes with the temperature of hot end, only as a result, with electrical measuring instrument measured the value of thermoelectric potential, can calculate the corresponding temperature value.