Thermocouple as a more commonly used temperature measuring instrument in industrial production, the utilization rate in all walks of life is very high, many people do not understand the working principle of this instrument, in actual use, can understand the working principle of thermocouple for usual use is also a lot of benefits. Here is a brief introduction to thermocouples and how they work
Widespread use of thermocouples:
As one of the most widely used temperature sensors in industrial temperature measurement, thermocouples, together with platinum thermal resistance, account for about 60% of the total number of temperature sensors, thermocouples are usually used with display instruments, etc., to directly measure the surface temperature of liquids, vapors and gaseous media and solids in the range of -40 ~ 1800 ° C in various production processes.
Advantages of thermocouples:
① High measurement accuracy;
② Wide measuring range;
③ Simple structure, easy to use thermocouple.
Basic principle of thermocouple temperature measurement
Thermocouple is a temperature sensing element, is a primary instrument, it directly measures the temperature, and converts the temperature signal into the thermoelectric motive force signal, and then converts the temperature of the measured medium through the electrical instrument (secondary instrument).
The basic principle of thermocouple temperature measurement is that two different components of the material conductor composed of a closed loop, when there is a temperature gradient at both ends, there will be current through the loop, at this time there is an electromotive force between the two ends - thermoelectric motive force, which is the so-called Seebeck effect.
The two different components of the homogeneous conductor is a thermal electrode, the higher temperature end is the working end, the lower temperature end is the free end, the free end is usually at a constant temperature. According to the function relationship between thermoelectric motive force and temperature, the index table of thermocouple is made. The index meter is obtained under the condition that the free end temperature is 0℃, and different thermocouples have different index meters.
When a third metal material is connected in the thermocouple loop, as long as the temperature of the two contacts of the material is the same, the thermocouple will generate a thermoelectric potential that will remain unchanged, that is, it will not be affected by the third metal access loop. Therefore, in the thermocouple temperature measurement, you can access the measuring instrument, after measuring the thermoelectric motive force, you can know the temperature of the measured medium.
