How to choose thermal resistance and thermocouple?
How to choose thermal resistance and thermocouple?Select according to the temperature measurement range: Thermocouples are generally selected above 500 ° C, and thermal resistances are generally selected below 500 ° C. Select based on measurement accuracy: Select thermal resistance for high accuracy requirements, and select thermocouple for low accuracy requirements. Select based on measurement range: thermocouple The measured temperature generally refers to the "point" temperature, and the measured temperature generally refers to the average space temperature. First,What is an armored thermocouple and what are its advantages? (1) This is the inorganic mineral insulated thermocouple cable. The thermal electrode, insulator, and sheath are formed by integral drawing. The outer surface seems to be covered with a layer of "armor", so it is called an armored thermocouple. (2) Compared with general assembled thermocouples, it has the advantages of high pressure resistance, good bendability, good oxidation resistance and long service life. Second. What are the graduation numbers of thermocouples and what are their characteristics? (1) There are several index numbers of thermocouples, such as S, R, B, N, K, E, J, and T. Among them, S, R, and B belong to precious metal thermocouples, and N, K, E, J, and T belong to inexpensive metal thermocouples. (2) The characteristic of T graduation number is that it has the highest accuracy level among all cheap metal thermocouples, and is usually used to measure temperatures below 300 ° C. Three, there are several ways of the lead-out wire of the thermal resistance, what are the effects? (1) There are 3 types of lead wires for thermal resistance: 2-wire system, 3-wire system, 4-wire system. (2) The wiring of 2-wire heating resistors is simple, but additional errors must be taken into the lead resistance. Therefore, it is not suitable for the manufacture of A-class thermal resistance, and the leads and wires should not be too long when used. The 3-wire system can eliminate the influence of the lead resistance, and the measurement accuracy is higher than that of the 2-wire system. As a process detection element, its most 4-wire system can not only eliminate the influence of lead resistance, but also eliminate the influence of the resistance when the connection wire resistance is the same. In high-precision measurement, 4-wire system is used. Fourth,How to choose the right compensation wire or cable? (1) The compensation wire and cable of the thermocouple are mainly used to extend the thermoelectromotive force of the thermocouple to the secondary instrument or control room. There are two types of compensation wires: extended type and compensated type. The extended type uses the same material as the thermal electrode, so the accuracy is higher; the compensated type uses a material with the thermoelectric potential characteristics of the thermal electrode, so the accuracy is not as high as the extended type. Five, correct selection of the diameter of the protection tube to ensure accurate measurement and control Theoretically: the smaller the diameter of the protective tube, the thinner the wall thickness, the faster the temperature response, the more precise the temperature control, the thicker and thicker the diameter, the greater the inertia, the slower the reaction, and the worse the temperature control accuracy. Of course, it is also necessary to consider the reasonable selection of factors such as corrosion, oxidation, pressure, friction and impact on the protective tube by the test substance.
Thermocouple sales 2
Thermocouple sales 1