The display accuracy of temperature sensor in the

The display accuracy of the temperature sensor of the high and low temperature test chamber

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in the high and low temperature test chamber, there is only one temperature sensor, whose main function is to sense the temperature change and convert it into an outputable digital signal; this article will mainly introduce the solution to maintain the best display accuracy of the temperature sensor. Its main body is now in the installation and use links. The following meityco will give you a detailed introduction: 1. Errors caused by improper installation, such as the installation position and insertion depth of thermocouples In other words, the thermocouple should not be installed too close to the door and the heating place, and the insertion depth should be at least 8 ~ 10 times the diameter of the protective tube; The space between the protective sleeve and the wall of the thermocouple is not filled with insulating materials, resulting in heat overflow or cold air intrusion in the furnace. Therefore, the gap between the protective tube of the thermocouple and the hole of the furnace wall should be blocked with insulating materials such as polyurethane foam or asbestos, so as to prevent the convection of cold and hot air from affecting the accuracy of temperature measurement; The cold end of the thermocouple is too close to the furnace body to make the temperature exceed 100 ℃; The installation of thermocouples should avoid strong magnetic fields and strong electric fields as far as possible, so thermocouples and power cables should not be installed in the same conduit to avoid introducing interference and causing errors; The thermocouple cannot be installed in the area where the measured medium rarely flows. When using the thermocouple to measure the gas temperature in the pipe, the thermocouple must be installed against the flow direction and fully in contact with the gas. 2. Errors caused by poor insulation, such as thermocouple insulation, excessive dirt or salt slag in protective tube and stay plate, lead to poor insulation between thermoelectric dipole and furnace wall, which is more serious at high temperature, which will not only cause the loss of thermal potential, but also introduce interference. 3. Thermal resistance error at high temperature, if there is a layer of coal ash on the protective tube and the dust is attached to it, the thermal resistance will increase and hinder the heat conduction. At this time, the temperature indication is lower than the true value of the measured temperature. Therefore, the outside of the thermocouple protection tube and the closed power supply should be kept clean to reduce the error. 4. The error heat introduced by thermal inertia. Due to the thermal inertia of the thermocouple, the indicated value of the instrument lags behind the change of the measured temperature, which is particularly prominent in rapid measurement. Therefore, thermocouples with thin Thermoelectrode and small diameter of protective tube should be used as far as possible. When the temperature measurement environment permits, the protective tube can even be removed. Due to the measurement lag, the amplitude of temperature fluctuation detected by thermocouple is smaller than that in the box. The larger the measurement lag is, the smaller the amplitude of thermocouple fluctuation is, and the greater the difference with the actual furnace temperature is. When thermocouples with large time constants are used for temperature measurement or control, although the temperature displayed by the instrument fluctuates very little, the actual box 2. According to the use of the machine and the service life of the oil, the fluctuation may be very large. In order to measure the temperature accurately, the thermocouple with small time constant should be selected. The time constant is inversely proportional to the heat transfer coefficient, and is directly proportional to the diameter of the hot end of the thermocouple, the density of the material and the specific heat. If you want to reduce the time constant, in addition to increasing the heat transfer coefficient, the most effective way is to minimize the size of the hot end of the steel strand, for example. In use, materials with good thermal conductivity and protective sleeves with thin pipe wall and small inner diameter are usually used. In the more precise temperature measurement, the bare wire thermocouple without protective sleeve is used, but the thermocouple is easy to be damaged, so it should be corrected and replaced when the experimental force, peak value of experimental force, beam displacement, experimental deformation and screen display of experimental curve are realized

source: Dongguan meitaike testing equipment Co., Ltd