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Factors Affecting RTD Temperature Sensor Measurement

Time：2017-12-18

　　RTD temperature sensor is a kind of temperature change measuring instruments, then the accuracy is the most basic requirements, the use of RTD temperature sensor in the process of the most important is to ensure the accuracy of measurement, reduce errors, the external factors The impact of measurement to a minimum, the following China Sensor Network experts to tell you about the impact of thermal resistance temperature sensor measurement factors.

　　Insert depth

　　Thermocouple temperature measurement point of choice is the most important. Temperature measurement point location, for the production process, must be typical, representative, otherwise it will lose the meaning of measurement and control. When the ambient temperature is low there will be heat loss. Resulting in thermocouple temperature sensor temperature is inconsistent with the measured temperature measurement error. In summary, the error caused by heat conduction is related to the insertion depth. The depth of the insertion and protection tube material. Metal protective tube because of its good thermal conductivity, the depth of the insertion should be deeper, thermal insulation properties of ceramic materials, can be inserted shallow. For engineering temperature measurement, the insertion depth is also related to the measurement object is still or flow state, the specific values should be determined experimentally.

　　Response time

　　The basic principle of the contact method temperature measurement is to test the temperature components to achieve thermal equilibrium. Therefore, in the temperature measurement need to maintain a certain time, in order to achieve the two heat balance. The length of time to keep, with the thermal components of the thermal response time. The thermal response time depends mainly on the sensor structure and measurement conditions, great differences. For gas medium, especially still gas, at least for more than 30min to reach balance; for liquid, as fast as 5min. For the temperature changes in the test site, especially the process of instantaneous changes, the whole process only 1 second, the sensor response time required in milliseconds. Therefore, the ordinary temperature sensor not only can not keep up with the temperature change rate of the object to be lagged, but also can not reach the heat balance and generate measurement error. The best choice for fast response sensor. In addition to the thermocouple in addition to the protective tube, the thermocouple measurement end diameter is also the main factor, that even thinner wire, the smaller diameter measurement, the shorter the thermal response time.

　　Thermal impedance increases

　　Thermocouple temperature sensor used at high temperatures, if the measured medium is gaseous, then the dust deposited on the surface of the protective tube will burn on the surface, so that the thermal resistance of the protective tube increases; if the measured medium is a melt, There will be slag deposition during use, which not only increases the response time of the thermocouple, but also lowers the indicated temperature. Therefore, in addition to regular verification, in order to reduce errors, frequent sampling is also necessary.

　　Heat radiation

　　The thermocouple temperature sensor inserted into the furnace for temperature measurement will be heated by the heat radiation from the hot object. Assuming that the gas in the furnace is transparent, and the temperature difference between the thermocouple and the furnace wall is large, temperature measurement errors will occur due to energy exchange. Under normal circumstances, in order to reduce the thermal radiation error, should increase the heat conduction, and the furnace wall temperature as close as possible thermocouple temperature. In addition, the thermocouple mounting position, should be as far as possible from the heat emitted from the solid, so that it can not radiate to the thermocouple surface; thermocouple heat shield with the best radiation.

　　The above four factors are the factors that affect the RTD temperature sensor measurement. Everyone in the daily measurement process must control the influence of these factors on the specific measurement process to ensure the accuracy of the measurement.

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