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What is the working principle of thermocouple?
Release time:
2024-02-29
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Abstract
The working principle of thermocouple (thermocouple principle) what is thermocouple?
This is to start from the principle of thermocouple temperature measurement. Thermocouple is a temperature sensing element and an instrument. It directly measures the temperature and converts the temperature signal into a thermal electromotive force signal, which is converted into an electrical instrument (secondary instrument). The temperature of the measured medium. Thermocouple temperature measurement is the basic principle of two different components of the material of the conductor to form a closed loop, when the two ends of the temperature gradient, there will be a current through the loop, at this time between the two ends of the Seebeck electromotive force-thermal electromotive force, which is the so-called Seebeck effect. Two different components of the homogeneous conductor for the hot electrode, the higher end of the temperature is the working end, the lower end of the temperature is the free end, the free end is usually at a constant temperature. According to the function relationship between thermal electromotive force and temperature, the thermocouple indexing table is made. The indexing table is obtained under the condition that the free end temperature is 0 ℃, and different thermocouples have different indexing tables. When the third metal material is connected to the thermocouple circuit, as long as the temperature of the two junctions of the material is the same, the thermoelectric potential generated by the thermocouple will remain unchanged, that is, it will not be affected by the third metal in the circuit. Therefore, in the thermocouple temperature measurement, can access the measuring instrument, measured after the thermal electromotive force, you can know the temperature of the measured medium. B: Thermocouple working principle: two different components of the conductor (called thermocouple wire or hot electrode) at both ends of the synthetic loop, when the junction temperature is not the same, in the loop will produce electromotive force, this phenomenon is called thermoelectric effect, and this electromotive force is called thermoelectric potential. Thermocouple is the use of this principle for temperature measurement, which is directly used to measure the temperature of the medium end is called the working end (also known as the measuring end), the other end is called the cold end (also known as the compensation end). Thermocouple is actually an energy converter, which converts heat energy into electric energy and measures temperature with the generated thermoelectric potential. For the thermoelectric potential of thermocouple, the following problems should be paid attention to: 1. The thermoelectric potential of thermocouple is the difference between the temperature functions at both ends of thermocouple, not the function of the temperature difference between the two ends of thermocouple; 2: The magnitude of the thermoelectric potential generated by the thermocouple, when the material of the thermocouple is uniform, it has nothing to do with the length and diameter of the thermocouple, but only with the composition of the thermocouple material and the temperature difference between the two ends. 3: When the material composition of the two thermocouple wires of the thermocouple is determined, the thermoelectric potential of the thermocouple is only related to the temperature difference of the thermocouple. If the temperature of the cold end of the thermocouple remains constant, the thermoelectric potential of the thermocouple is only a single-valued function of the temperature of the working end.
The thermocouple uses a closed circuit composed of two different materials; when the temperature of the 2 ends is different, there will be a current; and then through the measuring instrument, you can easily obtain the temperature of the medium.
Commonly used thermocouple materials are: thermocouple indexing number hot electrode material positive electrode negative electrode s platinum rhodium 10 pure platinum r platinum rhodium 13 pure platinum B platinum rhodium 30 platinum rhodium 6K nickel chromium nickel silicon t pure copper nickel j iron copper nickel n nickel chromium silicon e nickel chromium copper nickel
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