Introduction of Platinum rhodium thermocouple (S-type thermocouple)

Introduction of Platinum rhodium 10 platinum thermocouple (S-type thermocouple)

Platinum rhodium 10 platinum thermocouple (S-type thermocouple) is a precious metal thermocouple. The diameter of the coupling wire is specified as 0.5mm, and the allowable deviation is -0.015mm. The nominal chemical composition of the positive pole (SP) is platinum rhodium alloy, in which 10% rhodium is contained, 90% platinum is contained, and the negative pole (SN) is pure platinum, so it is commonly known as single platinum rhodium thermocouple. The long-term maximum operating temperature of the thermocouple is 1300 ℃, and the short-term maximum operating temperature is 1600 ℃. S-type thermocouple has the advantages of the highest accuracy, the best stability, wide temperature measurement range and long service life in the thermocouple series. It has good physical and chemical properties, thermoelectric stability and oxidation resistance at high temperatures, and is suitable for oxidizing and inert atmospheres. Because S type thermocouple has excellent comprehensive performance and conforms to the international temperature scale, it has long been used as the interpolation instrument of the international temperature scale. Although "ITS-90" stipulates that it will not be used as the internal inspection instrument of the international temperature scale in the future, the International Temperature Advisory Committee (CCT) considers that S type thermocouple can still be used to approximate the international temperature scale.

The measurement accuracy of S-type thermocouple is the highest when the normal long-term use temperature is about 800~1300 ℃, while the measurement accuracy is not high when the temperature is below 800 ℃, and the thermocouple is easily damaged when the long-term use temperature is above 1300 ℃. Therefore, selecting the thermocouple with correct graduation is an important factor to ensure the accuracy of temperature measurement.