There are many types of thermocouples, such as K-type, S-type, T-type, etc. Each type has its unique characteristics, which also lead to different characteristics and requirements in the calibration process.
The K-type thermocouple is one of the most commonly used. It has a relatively wide temperature measurement range, usually from -200℃ to 1300℃. When calibrating the K-type thermocouple, due to its relatively high sensitivity, the accuracy requirements for the calibration equipment are also relatively strict. Especially in the low temperature range, it is necessary to ensure that the calibration furnace or the constant temperature bath can accurately control the temperature, and the resolution of the reference thermometer is high enough to accurately measure small temperature changes. For example, in the calibration around -100℃, the temperature control accuracy should be within ±0.1℃.
The S-type thermocouple is mainly used for high temperature measurement, and its upper temperature limit can be as high as about 1600℃. When calibrating the S-type thermocouple, the focus is on the test of high temperature stability. The calibration equipment needs to be able to maintain a high temperature for a long time with extremely small temperature fluctuations. At the same time, since the thermoelectric potential change of the S-type thermocouple at high temperature is relatively small, a more accurate calculation method is needed in the data processing process to determine its error. For example, a more complex fitting algorithm is used to analyze the measurement data.
The T-type thermocouple is suitable for low temperature measurement, and the measurement range is generally between -200℃ and 350℃. For the calibration of the T-type thermocouple, the low temperature uniformity is the key. The calibration environment must ensure good temperature uniformity in the entire measurement space to avoid measurement errors caused by temperature gradients. Moreover, since its thermoelectric characteristics at low temperature are different from other types, the standard thermometer used for calibration also needs to be selected in a targeted manner to ensure the accuracy of calibration.
Different types of thermocouples have their own emphases in calibration. Only by fully understanding and following these characteristics and requirements can accurate thermocouple calibration be achieved and reliable guarantees be provided for various temperature measurement applications.
