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Temperature SensorThe feeling of temperature can be converted into signal output. Special attention should be paid to installation and use, otherwise it will cause errors in the temperature sensor and even cause safety hazards. This requires us to pay attention to the following points:

1. Errors caused by improper installation

In other words,Temperature SensorIt should not be installed too close to the door and heating place. The insertion depth of the temperature sensor should be at least 8~10 times the diameter of the protection tube. The gap between the protection sleeve and the thermocouple wall is not filled with insulating material, resulting in heat overflow or cold air in the furnace. Therefore, the gap between the thermocouple protection tube and the furnace wall hole should be sealed with refractory materials or asbestos rope and other insulating materials to avoid the convection of hot and cold air and affect the temperature measurement accuracy. The cold end of the thermocouple is too close to the furnace body, causing the temperature to exceed 100°C; the installation of the thermocouple should try to avoid strong magnetic fields and strong electric fields, so the thermocouple and power cable should not be installed in the same conduit to avoid errors caused by interference; the thermocouple cannot be installed in areas with a small flow rate of the medium to be measured. When using a thermocouple to measure the gas temperature in the tube, the thermocouple must be installed against the flow direction and in full contact with the gas.

2. Errors caused by poor insulation

If the temperature sensor is insulated, there is too much dirt or salt residue on the protection tube and wire plate, which will lead to poor insulation between the thermocouple and the furnace wall, especially at high temperatures, which will not only cause thermoelectric potential loss, but also cause interference, and the resulting error can sometimes reach hundreds of degrees.

3. Errors caused by thermal inertia

Due to the thermal inertia of the temperature sensor, the indicated value of the instrument lags behind the change of the measured temperature, especially in fast measurements. Therefore, thermocouples with smaller hot electrodes and smaller protection tube diameters should be used as much as possible. When the temperature measurement environment permits, the protection tube can even be removed. Due to the measurement lag, the temperature fluctuation amplitude detected by the thermocouple is smaller than the furnace temperature fluctuation amplitude. The greater the measurement lag, the smaller the thermocouple fluctuation amplitude, and the greater the difference with the actual furnace temperature. When the temperature is measured or controlled by a thermocouple with a large time constant, although the temperature fluctuation indicated by the instrument is very small, the actual temperature of the furnace may fluctuate greatly. In order to accurately measure the temperature, a thermocouple with a small time constant should be selected. The time constant is inversely proportional to the heat transfer coefficient and directly proportional to the thermocouple diameter, material density and specific heat. In use, materials with good thermal conductivity, thin tube walls and small inner diameter protective sleeves are usually used. In more accurate temperature measurement, bare wire thermocouples are used without protective sleeves, but the thermocouples are easily damaged and should be corrected and replaced.

4. Thermal resistance error

At high temperatures, if there is a layer of coal dust on the protection tube of the temperature sensor, the thermal resistance increases, preventing heat conduction, and the temperature indication is lower than the true value of the measured temperature. Therefore, the thermocouple should keep the outside of the tube clean to reduce errors.

Therefore, in order to better use and ensure safety, we need to pay attention to the above issues. Changzhou Ainuo Electronic Technology Co., Ltd. focuses on temperature control and diversified development.Temperature SensorIf you are interested in learning more, please call: 13506120522 for more information.