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• Name: screw thermocouple Index: K Temperature range: 0-400 ℃ Thermocouple is one of the most commonly used temperature detecting points in industry Its benefits are as follows: ① The size accuracy is excessive Because the thermocouple is in direct touch with the measured object, it isn't tormented by the intermediate medium ② The size differ is extensive Common thermocouples would be consistently measured from - 50 ℃ to + 1600 ℃ Some special thermocouples can measure - 269 ℃ (e gold iron nickel chromium) and + 2800 ℃ (e tungsten rhenium) ③ The constitution is simple and simple to apply Thermocouple is usually composed of two styles of diversified wires, and isn't always restricted by means of length and starting up There is a protecting sleeve outside, so it is very convenient to apply 1 Basic principle of thermocouple temperature dimension Two conductors or semiconductors A and B of different materials are welded collectively to kind a closed circuit, as shown in figure 2-1-1 It is shown that When there is a temperature distinction between the two attachment elements 1 and a couple of of conductors A and B, an electromotive power may be generated between them, in order that the A broad or small recent is shaped within the circuit, which is called thermoelectric effect Thermocouple is to apply this impact to paintings I made it 2 Type and constitution of thermocouple (1) Types of thermocouples Common thermocouples would be divided into common thermocouple and non-standard thermocouple The traditional thermocouple is the nationwide thermocouple The ordinary specifies the relationship between thermoelectric potential and temperature, the allowable error, and the thermocouple with unified standard commencement desk There are reveal devices for selection The non-standard thermocouple is inferior to the standard within the vary of use or order of magnitude In general, there is not any unified scale for thermocouple, which is principally used for measurement in some particular occasions Standardized thermocouple since January 1, 1988, all thermocouples and thermal resistors are produced consistent with IEC foreign standards, and seven sorts of standardized thermocouples (S, B, E, K, R, J, T) are designated as the unified design thermocouples in China (2) The constitution of thermocouple to be able to ensure the reliable and stable operation of thermocouple, its structure standards are as follows: ① The welding of the 2 thermoelectric electrodes of the thermocouple ought to be firm; ② The two thermoelectric poles needs to be properly insulated from each other to stop short circuit; ③ The connection between reimbursement twine and thermocouple loose finish must be convenient and reliable; ④ The protective sleeve can be able to ensure that the Thermoelectrode is solely isolated from harmful medium 3 Temperature compensation of thermocouple bloodless finish Because the cloth of thermocouple is usually costly (especially when using worthwhile metal), and the gap between temperature measuring level and device is terribly long, in an effort to save thermocouple material and decrease cost, repayment twine is usually used to increase the cold finish (free end) of thermocouple to the control room with steady temperature and connect it to instrument terminal It ought to be pointed out that the function of the thermocouple compensating twine is just to increase the Thermoelectrode and make the cold end of the thermocouple circulate to the device terminal in the control room It can't remove the impression of the temperature replace of the cold finish on the temperature size and has no compensating function Therefore, different tricks needs to be used to atone for the influence of temperature ≠ t0 at the bloodless end When using the thermocouple reimbursement wire, it's necessary to listen in on the model matching, the polarity cannot be wrong, and the temperature of the repayment wire and the thermocouple connection finish cannot exceed a hundred ℃

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