Factors Affecting the Measurement of Thermal Resistance Temperature Sensor

Thermal resistance temperature sensor is a kind of instrument for measuring temperature changes, so accuracy is the basic requirement. In the process of using thermal resistance temperature sensor, it is more important to ensure the accuracy of measurement, reduce the error, and reduce the influence of external factors on measurement to a small one. The following experts from China Sensor Trading Network will introduce the factors affecting the measurement of thermal resistance temperature sensor.

　　Insertion depth

The choice of thermocouple temperature measurement point is more important. The location of the temperature measuring point must be typical and representative for the production process, otherwise it will lose the significance of measurement and control. When the ambient temperature is low, there will be heat loss. The temperature of the thermocouple temperature sensor is inconsistent with the temperature of the measured object, resulting in temperature measurement error. In short, the error caused by heat conduction is related to the insertion depth. The insertion depth is related to the material of the protective tube. Metal protection tube because of its good thermal conductivity, its insertion depth should be deeper, ceramic material insulation performance is good, can be inserted shallower. For engineering temperature measurement, the insertion depth is also related to whether the measurement object is static or flowing, and the specific value should be determined by experiments.

　　Response time

The basic principle of temperature measurement by contact method is that the temperature measuring element should reach thermal balance with the measured object. Therefore, in the temperature measurement needs to maintain a certain period of time, in order to make the two reach thermal balance. The length of the holding time is related to the thermal response time of the temperature measuring element. The thermal response time mainly depends on the structure and measurement conditions of the sensor, and the difference is great. For gas medium, especially static gas, it should be kept at least 30min to reach equilibrium; for liquid, it should be faster than 5min. For the measured place where the temperature is constantly changing, especially the instantaneous change process, the whole process is only 1 second, and the response time of the sensor is required to be in the millisecond level. Therefore, the ordinary temperature sensor not only can not keep up with the temperature change speed of the measured object, but also can not reach the thermal balance and produce measurement error. It is better to choose a sensor that responds quickly. In addition to the influence of the protection tube, the diameter of the measuring end of the thermocouple is also the main factor, that is, the thinner the even wire, the smaller the diameter of the measuring end, the shorter the thermal response time.

　　Increased thermal impedance

Thermocouple temperature sensor used at high temperature, if the measured medium is gaseous, then the dust deposited on the surface of the protection tube will burn on the surface, so that the thermal impedance of the protection tube increases; if the measured medium is melt, In the process of use, there will be slag deposition, not only increases the response time of the thermocouple, but also makes the indicated temperature low. Therefore, in addition to regular verification, in order to reduce errors, frequent sampling is also necessary.

　　thermal radiation

The thermocouple temperature sensor inserted into the furnace for temperature measurement will be heated by the thermal radiation emitted by the high temperature object. It is assumed that the gas in the furnace is transparent, and when the temperature difference between the thermocouple and the furnace wall is large, the temperature measurement error will be generated due to energy exchange. In general, in order to reduce the thermal radiation error, the heat conduction should be increased, and the temperature of the furnace wall should be as close as possible to the temperature of the thermocouple. In addition, the installation position of the thermocouple should avoid the heat radiation emitted from the solid as much as possible, so that it can not be radiated to the surface of the thermocouple; the thermocouple is better with a heat radiation shielding sleeve.

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