Classification and temperature measurement range of thermocouples

The 8 standard thermocouples currently recommended by the International Electrotechnical Commission are as follows:

1. Platinum rhodium 10 platinum thermocouple (S-type thermocouple). Suitable for temperature measurement in oxidizing atmosphere, not recommended in reducing atmosphere, short-term use in vacuum environment. The long-term use temperature range is 0-1300 ℃, and the short-term use temperature range is 0-1400 ℃.

2. Platinum rhodium 13 platinum thermocouple (R-type). Applicable to S-type thermocouples in the field.

3. Platinum rhodium 30 platinum rhodium 6 thermocouple (type B). Suitable for temperature measurement in oxidizing atmosphere, its main feature is good stability, and no compensation wire is needed when the reference temperature is between 0~100 ℃. The long-term use temperature range is 0-1600 ℃, and the short-term use temperature range is 0-1800 ℃.

4. Nickel chromium nickel silicon thermocouple (K-type). Suitable for temperature measurement in oxidizing atmosphere, not recommended for use in reducing atmosphere. The temperature measurement range is determined by the diameter of the thermocouple, generally ranging from -200 to 1200 ℃ (the thermocouple diameter is 1.5mm at 1000 ℃, 2.5mm at 1000 ℃, and 3.2mm at 1200 ℃).

5. Nickel chromium silicon nickel silicon thermocouple (N-type). The temperature measurement range is 0-1300 ℃, with good stability.

6. Nickel chromium constantan thermocouple (type E). Suitable for temperature measurement in oxidizing and weakly reducing atmospheres, with a temperature range of -200~900 ℃.

7. Iron constantan thermocouple (J-type). Suitable for temperature measurement in oxidizing and reducing atmospheres and in vacuum, with a temperature range of -40~750 ℃.

8. Copper constantan thermocouple (T-type). Suitable for temperature measurement within the range of -200~400 ℃, its main features are high accuracy, good stability, high low-temperature sensitivity, and low price.

In addition to the internationally standardized thermocouples mentioned above, there are also non standardized thermocouples suitable for certain special temperature measurement situations and conditions:

1. Tungsten Rhenium 3-Tungsten Rhenium 25 Thermocouple (WRe3/25 Type). According to the American ASTMEE-988-84 standard, this thermocouple is suitable for inert gas, hydrogen gas, and vacuum, with a temperature measurement range of 0-2200 ℃.

2. Tungsten Rhenium 5-Tungsten Rhenium 26 Thermocouple (WRe5/26 Type). Suitable for temperature measurement in inert gases and hydrogen, and can also be used in vacuum environments, with a temperature range of 0-2200 ℃.

3. Nickel chromium gold iron thermocouple. Suitable for liquid nitrogen and liquid hydrogen media in the low temperature range of 0-273K.

4. Non metallic thermocouple. It has the characteristics of high thermoelectric potential and high melting point. The graphite titanium carbide thermocouple can measure high temperatures up to 2000 ℃ in carbon containing and neutral atmospheres; Boron carbide graphite thermocouple is hard, wear-resistant, high temperature resistant, and anti-oxidation. It has good linearity and high thermoelectric potential in the range of 600-2000 ℃. However, non-metallic thermocouples have poor reproducibility and lower mechanical strength.