Factors affecting the temperature measurement effect of integrated temperature sensor (transmitter)
Integrated temperature sensor (transmitter) is the most widely used thermometer in the industry, the temperature sensor is mainly a variety of models of thermal resistance, through the temperature transmitter into 4 to 20ma or 0 to 10v output, for plc and other control system applications. Now there are many manufacturers engaged in the production of integrated temperature sensors (transmitters), the quality difference is also very large, the choice should be carefully screened. So, what are the factors that affect the temperature measurement effect of the integrated temperature sensor (transmitter)? In summary, there are mainly the following points:
First: insertion depth
The selection of the temperature measurement point of the integrated temperature sensor (transmitter) is the most important. The location of the temperature measurement point must be typical and representative for the production process, otherwise it will lose the significance of measurement and control. When the integrated temperature sensor (transmitter) is inserted into the site under test, heat flow will be generated along the length of the sensor. Heat loss occurs when the ambient temperature is low. The temperature of the temperature sensor is inconsistent with that of the measured object, resulting in temperature measurement errors. In short, the error caused by heat conduction is related to the depth of insertion. The insertion depth is related to the material of the protective tube. Because of its good thermal conductivity, the metal protective tube should be inserted deeper, and the ceramic material has good thermal insulation performance and can be inserted shallower. For engineering temperature measurement, the insertion depth is also related to the measurement object is static or flowing state, such as the flow of liquid or high-speed air temperature measurement, will not be subject to the above restrictions, the insertion depth can be shallow, the specific value should be determined by the experiment.
Second: Response time
The basic principle of contact temperature measurement is that the temperature measuring element should reach thermal balance with the measured object. Therefore, it is necessary to maintain a certain time in temperature measurement in order to achieve thermal balance between the two. 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 of the temperature sensor and the measurement conditions, and the difference is great. Therefore, the ordinary temperature sensor not only can not keep up with the temperature change rate of the measured object lag, but also can not reach the thermal balance and produce measurement errors. It is best to choose a sensor that responds quickly. For the integrated temperature sensor (transmitter), in addition to the influence of the protective tube, the diameter of the measuring end of the temperature sensing element is also the main factor, that is, the smaller the temperature sensing element, the smaller the diameter of the measuring end, the shorter the thermal response time.
Third: thermal impedance increase
The integrated temperature sensor (transmitter) used at high temperatures, if the measured medium is gaseous, then the dust deposited on the surface of the protective tube will melt on the surface, so that the thermal impedance of the protective tube will increase; If the measured medium is a melt, there will be slag deposition during use, which not only increases the response time of the integrated temperature sensor (transmitter), but also makes the indicated temperature low. Therefore, in addition to regular verification, in order to reduce errors, frequent random inspection is also a necessary step.
The above are the three factors that affect the temperature measurement effect of the integrated temperature sensor (transmitter). When using, we should pay attention to ensure the best temperature measurement effect according to the actual situation. This article comes from Sensor House