Method for distinguishing the positive and negative poles of armored thermocouples
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As a type of thermocouple, armored thermocouples also have positive and negative poles. Can we accurately distinguish the positive and negative poles of armored thermocouples in the process of applying them?
The task principle of armored thermocouples is to form a closed circuit with two different materials of conductors. Whenever there is a temperature gradient at both ends, a circuit will occur, and current will flow through this circuit. At this time, there is electrical energy between the two ends, and this electrical energy is called thermoelectric potential, which is the famous Seebeck effect.
The two different materials of conductors are thermoelectric poles. Here, if the end with a higher temperature is the deformed task end, and vice versa, the end with a lower temperature is the free end. Under normal circumstances, the free end is in a constant temperature state.
Create a thermocouple calibration table based on the functional correlation between thermoelectric potential and temperature; The scale is a scale that is lost at a temperature of 0 ℃ at the free end, and there are differences in the scale of thermocouples.
In the entire circuit of the thermocouple, if a third metal material is connected and the temperature of the two contacts of the material is the same for a certain period of time, the thermoelectric potential generated by the thermocouple will remain stable and not be affected by the connection of the third metal material to the circuit.
Therefore, when using thermocouples for temperature measurement, a measuring instrument can be connected to measure the thermoelectric potential, and the temperature of the measured medium can be determined. When measuring temperature with a thermocouple, it is requested that the temperature of its cold end (the measuring end is the hot end, and the end connected to the measuring circuit through the process lead is called the cold end) remain stable, so that the magnitude of its thermoelectric potential is proportional to the measured temperature.
If the temperature changes during measurement, it will seriously affect the accuracy of the measurement.
The use of certain methods to compensate for the effects caused by temperature changes at the cold end is called thermocouple cold end compensation deformity. Use common compensating wires to connect with measuring instruments.
