One of factors influencing the insertion depth
The choice of thermocouple temperature measurement points is the most important. The location of the temperature measurement points, for the production process, must be typical and representative, otherwise you will lose the meaning of measurement and control. Thermocouple insertion under test site, along the long degree of direction of the sensor will produce heat. When the environment temperature low heat loss. The thermocouple temperature sensor do not agree with the temperature of the measured object and produce temperature measurement error. In a word, the error induced by heat conduction, related to the insertion depth. And inserted into the deep degree related to the protection tube material. Metal protection tube because of its thermal performance is good, the insert depth should be a little bit deep, ceramic material thermal insulation performance is good, can be inserted into the light. For engineering measurement, the insertion depth and measurement object is static or flowing state, such as the flow of liquid or high-speed airflow temperature measurement, will not be restricted by the above, the insert depth is shallow, some concrete numerical value should be determined by experiment.
Factors affecting the second thermal impedance increase
Use the thermocouple temperature sensor in high temperature, if the medium to be measured for the gas, so protecting tube surface deposition of dust will burn melt on the surface of the thermal impedance in the protecting tube increase; If the medium to be measured is melt, slag deposition in use process, not only increase the response time of the thermocouple, and also indicate the temperature is low.
The third factors affecting the response time
Contact method of temperature measurement is the basic principle of temperature measuring element to reach thermal equilibrium with the object being measured. When measuring temperature, therefore, need to keep a certain time and to make both reach thermal equilibrium. While keeping the length of time, with temperature measuring elements related to the thermal response time. And thermal response time depends on the structure of the sensor and measurement conditions, the difference is great. For the gas medium, especially the static gas, at least should be a balance of more than 30 min to reach; For liquid, the fastest also want to in more than 5 min. Measured, for the temperature changing especially instant change process, the whole process of only 1 second, insist on the sensor response time in milliseconds. Ordinary temperature sensor, therefore, not only to keep pace with the speed of change in the temperature of the object appear lags behind, and the measurement error due to reach thermal equilibrium. Had better choose fast response of the sensor. Except for thermocouple protection tube, diameter of the measuring junction of the thermocouple, and the main factors that accidentally silk the thinner, measuring the diameter is smaller, the shorter its thermal response time.
The last is the thermal radiation
Above is the four factors influencing the thermocouple temperature sensor, we should pay attention to when using, according to the actual situation, to ensure that the best measurement results.
