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How the thermocouple works

Release date: 2017-07-20 09:44:06 Visits: 677

Thermocouple is the temperature measurement and control instruments commonly used in temperature measurement components, it directly measure the temperature, and the temperature signal into a thermoelectromotive force signal, through the electrical instrument into the measured medium temperature. The appearance of the various thermocouples is often very different because of the need, but their basic structure is roughly the same.

Thermocouple temperature measurement of the basic working principle is composed of two different components of the material composition of the closed loop, when there is a temperature gradient at both ends, the circuit will have a current through, there is between the two ends of the electromotive force - thermoelectromotive force, This is called the Seebeck effect.

Two different components of the homogeneous conductor for the thermal electrode, the higher the temperature of the end of the working end, the lower end of the temperature is free, the free end is usually at a constant temperature. According to the relationship between the thermoelectromotive force and the temperature, the thermocouple indexing table is made. The indexing table is obtained under the condition that the free end temperature is 0 ℃, and the different thermocouples have different indexing tables.

When the third metal material is connected to the thermocouple circuit, the thermoelectric power generated by the thermocouple will remain constant as long as the temperature of the two contacts of the material is the same, that is, not affected by the third metal access circuit. Therefore, the thermocouple temperature measurement, access to measuring instruments, measured thermoelectromotive force, you can know the temperature of the measured medium.

Thermocouple temperature measurement requirements of its cold end (the measurement side of the hot end, through the lead and the measurement circuit connected to the end of the cold side) to maintain the same temperature, the thermal potential of the temperature and the measured temperature was a certain proportion.

During the measurement, the cold end (ambient) temperature changes will seriously affect the accuracy of the measurement. In the cold side to take some measures to compensate for the cold side of the temperature changes caused by the impact of the cold side of the thermocouple compensation as normal. A special compensating wire displacement sensor for connection to a measuring instrument.
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