What do the "indexing numbers" of thermocouples and temperature measuring instruments mean?
The thermocouple indexing numbers are mainly S, R, B, N, K, E, J, T and so on. Among them, S, R, B belong to precious metal thermocouples, N, K, E, J, T belong to cheap metal thermocouples.
The characteristic of S indexing number is that it has strong anti-oxidation performance. It is suitable for continuous use in oxidizing and inert atmosphere. The long-term use temperature is 1400 ℃ and the short-term temperature is 1600 ℃. Among all thermocouples, the accuracy grade of the S index number is the highest, and it is usually used as a standard thermocouple;
Compared with the S index number, the R index number is about 15% larger than the thermal electromotive force, and the other properties are almost the same;
The B index number has a very small thermoelectromotive force at room temperature, so it is generally not necessary to compensate for the wire during the measurement. Its long-term use temperature is 1600 ℃, short-term 1800 ℃. It can be used in an oxidizing or neutral atmosphere, and can also be used for a short time under vacuum conditions.
The characteristics of the N index number are the high temperature oxidation resistance at 1300 ℃, the long-term stability of the thermoelectromotive force and the reproducibility of the short-term thermal cycle, the resistance to nuclear radiation and the low temperature resistance, and can partially replace the S index number Thermocouple;
The characteristic of K indexing number is that it has strong anti-oxidation performance. It is suitable for continuous use in oxidizing and inert atmosphere. The long-term use temperature is 1000 ℃ and the short-term temperature is 1200 ℃. The most widely used among all thermocouples;
The characteristic of E indexing number is that among the commonly used thermocouples, the thermoelectromotive force is the largest, that is, the sensitivity is the highest. It is suitable for continuous use in oxidizing and inert atmosphere, the use temperature is 0-800 ℃;
The characteristic of J indexing number is that it can be used in both oxidizing atmosphere (operating temperature upper limit 750 ℃) and reducing atmosphere (operating temperature upper limit 950 ℃), and is resistant to H2 and CO gas corrosion, and is mostly used in oil refining and chemical industry;
The characteristic of T index number is that it has the highest accuracy level among all inexpensive metal thermocouples, and is usually used to measure the temperature below 300 ℃
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