The difference between R-type thermocouple and S-type thermocouple

Introduction: Platinum rhodium 10 platinum thermocouple (S-type thermocouple) is a precious metal thermocouple. The diameter of the thermocouple is defined as 0.5mm, with a deviation of -0.015mm. The nominal chemical identity of its positive electrode (SP) is platinum rhodium alloy, which contains 10% rhodium and 90% platinum. The negative electrode (SN) is pure platinum, hence it is commonly known as a single platinum rhodium thermocouple. The temporary maximum application temperature of this thermocouple is 1300 ℃, and the short-term maximum application temperature is 1600 ℃.

Features: S-type thermocouples have the highest degree of stability, wide temperature measurement range, and long application life in the thermocouple series. It has excellent physical and chemical properties, stable thermoelectric potential, and good antioxidant function at low temperatures, making it suitable for use in oxidizing and inert atmospheres. Due to the excellent comprehensive function of S-type thermocouples, which are suitable for temperature scale applications, they have been temporarily used as an interpolation instrument for temperature scales. Although "ITS-90" is no longer designated as an external instrument for temperature scales, the Temperature Consultation Committee (CCT) believes that S-type thermocouples can still be used to approximate temperature scales.

Problem: The lack of S-type thermocouples lies in their thermoelectric potential, which is relatively small and has low sensitivity. The machine strength decreases at low temperatures, making it highly sensitive to infections. Precious metal materials are expensive, so the one-time investment is relatively large.

(R-type thermocouple) Platinum rhodium 13 platinum thermocouple

Introduction: Platinum rhodium 13 platinum thermocouple (R-type thermocouple) is a precious metal thermocouple. The diameter of the wire is designated as 0.5mm, with a deviation of -0.015mm. The nominal chemical identity of its positive electrode (RP) is platinum rhodium alloy, which contains 13% rhodium and 87% platinum. The negative electrode (RN) is pure platinum, with a temporary maximum application temperature of 1300 ℃ and a short-term maximum application temperature of 1600 ℃.

Features: R-type thermocouples have the highest degree of stability, wide temperature measurement range, and long application life in the thermocouple series. It has excellent physical and chemical properties, stable thermoelectric potential, and good antioxidant function at low temperatures, making it suitable for use in oxidizing and inert atmospheres. Because the comprehensive function of R-type thermocouples is comparable to that of S-type thermocouples, it has always been difficult to promote in China. Except for temperature measurement on inlet equipment, temperature measurement at sea is rarely adopted. Between 1967 and 1971, the three major research institutions of NPL in the UK, NBS in the US, and NRC in Canada stopped a collaborative study. The results showed that the stability and reproducibility of R-type thermocouples were better than those of S-type thermocouples. However, China has not yet developed research in this area.

Problem: The lack of R-type thermocouples lies in their thermoelectric potential, which is relatively small and has low sensitivity. The machine strength decreases at low temperatures, making it highly sensitive to infections. Precious metal materials are expensive, so the one-time investment is relatively large.