What does the "grading number" of thermocouples and temperature measuring instruments mean?
The division marks of thermocouples mainly include S, R, B, N, K, E, J, T, etc. Among them, S, R, and B belong to precious metal thermocouples, while N, K, E, J, and T belong to low-cost metal thermocouples.
The characteristic of S scale is strong antioxidant performance, suitable for continuous use in an oxidizing and inert atmosphere, with a long-term use temperature of 1400 ℃ and a short-term use temperature of 1600 ℃. Among all thermocouples, the S scale has the highest degree level and is usually used as a standard thermocouple;
Compared with the S scale, the R scale has almost identical performance except for a 15% increase in thermoelectric potential;
The B division mark has a very small thermoelectric potential at room temperature, so compensation wires are generally not needed during measurement. Its long-term usage temperature is 1600 ℃, and its short-term usage temperature is 1800 ℃. It can be used in oxidizing or neutral atmospheres, as well as for short-term use under vacuum conditions.
The characteristics of the N scale are strong high-temperature oxidation resistance at 1300 ℃, good long-term stability of thermoelectric potential and reproducibility of short-term thermal cycles, and good resistance to nuclear irradiation and low temperature. It can partially replace the S scale thermocouple;
The characteristic of K scale is strong antioxidant performance, suitable for continuous use in an oxidizing and inert atmosphere, with a long-term use temperature of 1000 ℃ and a short-term use temperature of 1200 ℃. Widely used in all thermocouples;
The characteristic of the E-scale mark is that it has a high thermoelectric potential and sensitivity among commonly used thermocouples. Suitable for continuous use in an oxidizing and inert atmosphere, with a temperature range of 0-800 ℃;
The characteristic of the J division mark is that it can be used in both oxidizing atmospheres (with an upper temperature limit of 750 ℃) and reducing atmospheres (with an upper temperature limit of 950 ℃), and is resistant to H2 and CO gas corrosion. It is commonly used in refining and chemical industries;
The characteristic of the T-scale is that it has the highest accuracy level among all low-cost metal thermocouples and is usually used to measure temperatures below 300 ℃.
