What are the advantages and disadvantages of platinum and rhodium thermocouple compared to ordinary thermocouple?

Speaking of platinum and rhodium thermocouple may be a lot of people do not know what he is, we have a certain understanding of the thermocouple, but for platinum and rhodium thermocouple people do not know what characteristics, in fact, platinum and rhodium is a precious metal, And platinum and rhodium thermocouple is made of platinum and rhodium, the following we come together to find out about it

Platinum-rhodium thermocouple, also known as high-temperature precious metal thermocouple, platinum and rhodium has a single platinum and rhodium (platinum rhodium 10-platinum and rhodium) and double platinum and rhodium (platinum and rhodium 30-platinum rhodium 6) points, they are used as temperature sensors, Transmitter, regulator and display instrument, etc., to form a process control system for direct measurement or control of various production processes in the range of 0- 1800 ℃ fluid, steam and gas medium and solid surface temperature.

Platinum and rhodium thermocouple is composed of two different components of the conductor at both ends of the circuit into the loop, when the two junction temperature is different, it will generate heat in the circuit. If there is a temperature difference between the working end of the thermocouple and the reference end, the display instrument will indicate the temperature value corresponding to the thermoelectric potential generated by the thermocouple. The thermoelectric heat of the platinum and rhodium thermocouple will increase with the increase of the temperature at the measuring end. Its size is only related to the temperature of the thermocouple material and both ends, regardless of the length and diameter of the hot electrode. The appearance of various platinum and rhodium thermocouples is often very different because of the need, but their basic structure is roughly the same, usually by the thermal electrode, insulation sleeve protection and junction box and other major components.

Advantages: Platinum and rhodium thermocouple in the thermocouple series with the highest accuracy, the best stability, temperature range, long life, high temperature upper limit advantages. Suitable for use in oxidizing and inert atmospheres, but also for short term use in vacuum, but not in a reducing atmosphere or in a metal or nonmetallic vapor atmosphere. A significant advantage of the Type B thermocouple is that compensation is not required with compensating leads because the thermoelectric power is less than 3μV in the range of 0 to 50 ° C.

Disadvantages: Platinum and rhodium thermocouple lack of thermoelectric power rate is small, low sensitivity, high temperature mechanical strength, expensive precious metals, and thus a one-time investment. Platinum and rhodium thermocouple is composed of two different components of the conductor at both ends of the circuit into the loop, when the two junction temperature is different, it will generate heat in the loop. If there is a temperature difference between the working end of the thermocouple and the reference end, the display instrument will indicate the temperature value corresponding to the thermoelectric potential generated by the thermocouple.