Description of the operating temperature of platinum-rhodium thermocouple

Platinum-rhodium thermocouples are also called high-temperature precious metal thermocouples. Platinum-rhodium thermocouples are divided into single platinum-rhodium (platinum-rhodium 10-platinum-rhodium) and double platinum-rhodium (platinum-rhodium 30-platinum-rhodium 6). As temperature measurement sensors, they are usually used in conjunction with temperature transmitters, regulators and display instruments to form process control systems to directly measure or control the temperature of fluids, steam and gas media and solid surfaces within the range of 0-1700℃ in various production processes.

The operating temperature is -200~1300℃. Platinum-rhodium thermocouples have the advantages of good linearity, large thermoelectric potential, high sensitivity, good stability and uniformity, strong antioxidant performance, low price, and no influence of short-range ordering. Its comprehensive performance is better than that of K-type thermocouples, and it is a very promising thermocouple. N-type thermocouples cannot be used directly in sulfur, reducing or reducing, oxidizing alternating atmospheres and vacuum at high temperatures.

Therefore, they cannot be replaced by EN and TN. The measurement temperature range of the iron-constantan thermocouple is -200~1200℃, but the commonly used temperature range is 0~750℃. The J-type thermocouple has the advantages of good linearity, large thermoelectric potential, high sensitivity, good stability and uniformity, and low price, and is widely used by users. Platinum-rhodium thermocouples can be used in vacuum, oxidation, reduction and inert atmospheres, but the positive iron oxidizes quickly at high temperatures, so the use temperature is limited, and it cannot be directly used in sulfiding atmospheres at high temperatures without protection.

The platinum-rhodium thermocouple contains 10% rhodium and 90% platinum, and the negative electrode (SN) is pure platinum, so it is commonly known as a single platinum-rhodium thermocouple. The maximum long-term use temperature of this thermocouple is 1300℃, and the maximum short-term use temperature is 1600℃. The S-type thermocouple has the advantages of the highest accuracy, best stability, wide temperature measurement range, and long service life in the thermocouple series. It has good physical and chemical properties, thermoelectric potential stability and good oxidation resistance at high temperatures, and is suitable for oxidizing and inert atmospheres. Due to its excellent comprehensive performance, platinum-rhodium thermocouples that conform to the international temperature scale have long been used as interpolation instruments for the international temperature scale.