1. The basic principle of thermocouple temperature measurement is to weld two different material conductors or semiconductors A and B together to form a closed loop. When there is a temperature difference between the two sticking points 1 and 2 of the conductors A and B, an electromotive force is generated between the two sticking points 1 and 2 so that a current of a size is formed in the loop. This phenomenon is called a thermoelectric effect. Thermocouples use this effect to work.
2. Types and Structures of Thermocouples (1) Types of Thermocouples Thermocouples can be classified into standard thermocouples and non-standard thermocouples. The called standard thermocouple refers to thermocouples whose national standards stipulate the relationship between thermoelectric potential and temperature, allowable errors, and a unified standard indexing table. It has its own display instrument for selection. Non-standardized thermocouples are less than standard thermocouples in terms of range of use or magnitude, and there are generally no uniform indexing tables, which are mainly used for measurement in certain special occasions. Standardized Thermocouples From January 1, 1988, thermocouples and thermal resistances were all produced according to IEC international standards, and seven standardized thermocouples designated as S, B, E, K, R, J, and T were designed for unified design in China. Thermocouples.
Thermocouple structure in order to ensure the reliable and stable thermocouple work, its structure requirements are as follows:
1 The welding of the two hot electrodes forming the thermocouple must be firm;
2 The two hot electrodes should be well insulated from each other to prevent short circuit;
3 The connection between the compensation wire and the free end of the thermocouple should be convenient and reliable;
4 The protective sleeve should ensure that the hot electrode is fully isolated from harmful media.
3. Thermocouple cold junction temperature compensation due to thermocouple materials are generally more expensive (especially when using precious metals), and the temperature measurement point to the instrument is very far, in order to save thermocouple materials, reduce costs, usually using compensation wire to thermoelectric The even cold end (free end) extends into a relatively stable temperature control room and is connected to the meter terminals. It must be pointed out that the role of thermocouple compensation wire only extends the thermode, so that the cold junction of the thermocouple moves to the instrument terminal of the control room. It does not eliminate the influence of the temperature change of the cold junction on the temperature measurement and does not compensate. Therefore, other correction methods need to be used to compensate for the effect of temperature at the cold junction temperature t0≠0°C. When using a thermocouple to compensate for the wire, it must be noted that the model matches, and the polarity cannot be connected wrongly. The temperature of the connecting wire of the compensation wire and the thermocouple cannot exceed 100°C. Thermal resistance Thermistor is the most commonly used temperature detector in the low-temperature region. Its main features are high measurement accuracy and stable performance.
2. Types and Structures of Thermocouples (1) Types of Thermocouples Thermocouples can be classified into standard thermocouples and non-standard thermocouples. The called standard thermocouple refers to thermocouples whose national standards stipulate the relationship between thermoelectric potential and temperature, allowable errors, and a unified standard indexing table. It has its own display instrument for selection. Non-standardized thermocouples are less than standard thermocouples in terms of range of use or magnitude, and there are generally no uniform indexing tables, which are mainly used for measurement in certain special occasions. Standardized Thermocouples From January 1, 1988, thermocouples and thermal resistances were all produced according to IEC international standards, and seven standardized thermocouples designated as S, B, E, K, R, J, and T were designed for unified design in China. Thermocouples.
Thermocouple structure in order to ensure the reliable and stable thermocouple work, its structure requirements are as follows:
1 The welding of the two hot electrodes forming the thermocouple must be firm;
2 The two hot electrodes should be well insulated from each other to prevent short circuit;
3 The connection between the compensation wire and the free end of the thermocouple should be convenient and reliable;
4 The protective sleeve should ensure that the hot electrode is fully isolated from harmful media.
3. Thermocouple cold junction temperature compensation due to thermocouple materials are generally more expensive (especially when using precious metals), and the temperature measurement point to the instrument is very far, in order to save thermocouple materials, reduce costs, usually using compensation wire to thermoelectric The even cold end (free end) extends into a relatively stable temperature control room and is connected to the meter terminals. It must be pointed out that the role of thermocouple compensation wire only extends the thermode, so that the cold junction of the thermocouple moves to the instrument terminal of the control room. It does not eliminate the influence of the temperature change of the cold junction on the temperature measurement and does not compensate. Therefore, other correction methods need to be used to compensate for the effect of temperature at the cold junction temperature t0≠0°C. When using a thermocouple to compensate for the wire, it must be noted that the model matches, and the polarity cannot be connected wrongly. The temperature of the connecting wire of the compensation wire and the thermocouple cannot exceed 100°C. Thermal resistance Thermistor is the most commonly used temperature detector in the low-temperature region. Its main features are high measurement accuracy and stable performance.
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