Advantages, Principles, and Temperature Measurement Range Analysis of Platinum Rhodium Thermocouples

Nowadays, platinum rhodium thermocouples are still relatively widely used in the industrial and chemical fields, especially in power plants, chemical production, high-temperature furnaces, and other production areas. Platinum rhodium thermocouples are almost always used as temperature measuring elements, and the proportion of other types of thermocouples is very small. Large enterprise projects use reliable platinum rhodium thermocouples mainly because they have many advantages.

The advantages of platinum rhodium thermocouples mainly include accurate measurement, good temperature performance, high temperature resistance, long service life, and it can be suitable for different oxidizing and inert atmospheres. Its application range and field are extremely wide. As a temperature sensing element, it generally needs to be used in conjunction with temperature transmitters, displays, and other components for temperature control as a thermal engineering set. The temperature measurement range of platinum rhodium thermocouples is very wide, which can measure gases, liquids, solids in the range of 0-1800 ° C, and can also be used for steam measurement.

The working principle of platinum rhodium thermocouple:

The working principle of platinum rhodium thermocouple is that when two conductors with different compositions are connected at both ends to form a circuit, a thermal current will be generated in the circuit when the temperature of the two junction points is different. If there is a temperature difference between the working end and the reference end of the thermocouple, the display instrument will indicate the temperature value corresponding to the thermoelectric potential generated by the thermocouple.

Platinum rhodium thermocouples are divided into various models based on the measured temperature. It is recommended to use a single platinum rhodium thermocouple (Platinum Rhodium 10 Platinum) when the measured temperature is normally between 1000~1300 ℃. If the measured temperature is normally between 1200~1600 ℃, it is recommended to use a dual platinum rhodium thermocouple (Platinum Rhodium 30- Platinum Rhodium 6) to ensure the service life of the platinum rhodium thermocouple within the temperature range used.

Platinum rhodium thermocouple is a precious metal thermocouple. The diameter of the thermocouple wire is specified as 0.5mm, with an allowable deviation of -0.015mm. The nominal chemical composition of its positive electrode (BP) is platinum rhodium alloy, containing 30% rhodium and 70% platinum. The negative electrode (BN) is platinum rhodium alloy, containing 6% rhodium, hence it is commonly known as a double platinum rhodium thermocouple. The long-term high usage temperature of this thermocouple is 1600 ℃, and the short-term high usage temperature is 1800 ℃.