Pt-Rh thermocouple has the highest accuracy, best stability, wide temperature range, long service life and high temperature limit in thermocouple series. Suitable for oxidizing and inert atmospheres or for short-term use in a vacuum, but not for reducing atmospheres or atmospheres containing metallic or non-metallic vapors. B type thermocouple is an obvious advantage don't need a compensation for the compensation conductor, because in the range of 0 ~ 50 ℃ and internal potential less than 3 mu V.
Disadvantages: the disadvantages of platinum and rhodium thermocouple are thermoelectric potential, low thermoelectric potential rate, low sensitivity reading, low mechanical strength under high temperature, very sensitive to pollution, precious metal materials are expensive, thus large one-time investment.
The principle of pt-rh thermocouple is that the pt-rh thermocouple is composed of two conductors of different components. When the temperature of the two joints is different, the thermal current will be generated in the circuit. If there is a temperature difference between the working end and the reference end of the thermocouple, the display meter will indicate the corresponding temperature value of the thermoelectric potential generated by the thermocouple.
Platinum rhodium thermocouple choice: measurement of temperature during 1000 ~ 1300 ℃ normally recommended single platinum-rhodium thermocouple (10 - platinum platinum rhodium), measuring the temperature of the normal during 1200 ~ 1600 ℃ suggest using double platinum rhodium thermocouple (30 - platinum rhodium platinum rhodium 6), so you use temperature range to ensure the service life of platinum-rhodium thermocouple.
