What are the advantages of a thermometer made of platinum rhodium alloy thermocouple compared to a typical household thermometer?

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Platinum rhodium thermocouples, also known as high-temperature precious metal thermocouples, are divided into single platinum rhodium (platinum rhodium 10 platinum rhodium) and double platinum rhodium (platinum rhodium 30 platinum rhodium 6). They are used as temperature measurement sensors and are usually used in conjunction with temperature transmitters, regulators, and display instruments to form process control systems. They are used to directly measure or control the temperature of fluids, vapors, gas media, and solid surfaces within the range of 0-1800 ℃ in various production processes.

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 thermocouple has a long-term high usage temperature of 1600 ℃ and a short-term high usage temperature of 1800 ℃.

Advantages: Platinum rhodium thermocouples have high accuracy, good stability, wide temperature measurement range, long service life, and high temperature measurement upper limit in the thermocouple series. Suitable for oxidizing and inert atmospheres, and can also be used in vacuum for a short period of time, but not suitable for reducing atmospheres or atmospheres containing metal or non-metal vapors. A significant advantage of B-type thermocouples is that they do not require compensation wires, as the thermoelectric potential is less than 3 μ V within the range of 0-50 ℃.

Disadvantages: The shortcomings of platinum rhodium thermocouples are thermoelectric potential, low thermoelectric potential, low sensitivity reading, decreased mechanical strength at high temperatures, high sensitivity to pollution, expensive precious metal materials, and therefore large one-time investment.

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.

Selection of Platinum Rhodium Thermocouples: It is recommended to use a single platinum rhodium thermocouple (Platinum Rhodium 10 Platinum) when measuring temperatures between 1000 and 1300 ℃, and a double platinum rhodium thermocouple (Platinum Rhodium 30 Platinum Rhodium 6) when measuring temperatures between 1200 and 1600 ℃. This ensures the service life of the platinum rhodium thermocouple within the temperature range used