"Graduation number" in thermocouple and temperature measuring instrument
The "graduation numbers"/thermocouples in thermocouples and temperature measuring instruments mainly include S, R, B, N, K, E, J, T, etc. Among them, S, R, and B belong to noble metal thermocouples, and N, K, E, J, and T belong to cheap metal thermocouples.
The S graduation number is characterized by strong anti-oxidation performance, and is suitable for continuous use in an oxidizing and inert atmosphere. The long-term use temperature is 1400 ° C, and the short-term use temperature is 1600 ° C. Among all thermocouples, the S graduation number has the highest accuracy grade and is usually used as a standard thermocouple;
Compared with the S graduation number, the thermal electromotive force of the R graduation number is about 15% larger, and the other performances are almost the same;
The thermal electromotive force of the B graduation number is extremely small at room temperature, so there is generally no need for compensation wires during measurement. Its long-term use temperature is 1600°C and short-term 1800°C. It can be used in oxidizing or neutral atmosphere, and can also be used in vacuum condition for a short time.
The N graduation number is characterized by strong high-temperature oxidation resistance at 1300 °C, long-term stability of thermoelectromotive force and good reproducibility of short-term thermal cycle, good nuclear radiation resistance and low temperature resistance, and can be partially replaced
S graduation number thermocouple;
The K graduation number is characterized by strong anti-oxidation performance, and it is suitable for continuous use in an oxidizing and inert atmosphere. The long-term use temperature is 1000 ° C, and the short-term use temperature is 1200 ° C. The most widely used of all thermocouples;
The characteristic of E graduation number is that among commonly used thermocouples, its thermal electromotive force is the largest, that is, the sensitivity is the highest. It should be used continuously in an oxidizing and inert atmosphere, and the operating temperature is 0-800°C;
The characteristic of J graduation number is that it can be used in both oxidizing atmosphere (the upper limit of operating temperature is 750°C), and it can also be used in reducing atmosphere (upper limit of operating temperature is 950°C), and it is resistant to H2 and CO gas corrosion, and is mostly used in oil refining and chemical industry;
The T graduation number is characterized by the highest accuracy grade among all base metal thermocouples, and is usually used to measure temperatures below 300°C.
