Five aspects to teach you how to use thermocouples correctly

Thermocouples are highly accurate and cost-effective products in the development of measurement sensors, making them a widely used type of temperature measuring element. They directly measure temperature and convert the temperature signal into a thermoelectric potential signal, which is then converted into the temperature of the measured medium through an electrical meter (secondary instrument). In order to improve the accuracy of measurement, reduce measurement errors, and extend the service life, it is required that the users not only have instrument operation skills, but also have knowledge in physics, chemistry, and materials. Based on years of on-site practical experience, Beijing Haohai Yuntian provides a detailed introduction to the measurement errors and precautions of thermocouples, so that everyone can better use thermocouples.
During the use of thermocouples, it is important to pay attention to the following 5 issues:

1. The division mark of the thermocouple must be consistent with the thermocouple required by the temperature measurement and control instrument used;
2. Reasonably select the material and outer diameter size of the thermocouple sheath to ensure sufficient strength and adaptability to the measured environmental gas. The surface of the outer sleeve should be kept clean. If there are stains on the surface, it will increase the thermal resistance and the measured temperature will be lower than the actual temperature;

3. The location for installing thermocouples should be as far away as possible from environments with strong electromagnetic fields, avoiding high-power power lines to prevent additional interference signals from being introduced by temperature measuring instruments;

4. Thermocouples cannot operate at very high allowable temperatures for long periods of time, otherwise it will cause changes in the thermocouple material, resulting in increased measurement errors and thermocouple damage. To reduce the thermal inertia of thermocouples when measuring low temperatures, bottom or exposed thermocouples can be used;

5. It is necessary to regularly check whether the electrode and outer sleeve are intact. If local diameter reduction or severe corrosion of the outer sleeve surface is found, the use should be stopped immediately and a new thermocouple should be replaced. After the thermocouple is damaged, the damaged end can be removed, or the measuring end can be swapped with the reference end and re welded. After verification, it can still be used.