Platinum and rhodium thermocouples are precious metal thermocouples. The diameter of the wire is specified as 0.5mm, and the allowable deviation is -0.015mm. The nominal chemical composition of the positive electrode (BP) is platinum-rhodium alloy, of which 30% is rhodium, 70% is platinum, and the negative electrode (BN) is platinum-rhodium alloy The content of rhodium is 6%, so it is commonly known as double platinum rhodium thermocouple. The long-term maximum use temperature of the thermocouple is 1600 ℃, and the short-term maximum use temperature is 1800 ℃.
Advantages: Platinum and rhodium thermocouples have the highest accuracy, best stability, wide temperature range, long service life and high temperature limit in the thermocouple series. It is suitable for oxidizing and inert atmosphere, and can also be used in vacuum for a short time, but it is not suitable for reducing atmosphere or atmosphere containing metal or non-metal vapor. An obvious advantage of the B-type thermocouple is that no compensation wire is needed for compensation, because the thermoelectric potential is less than 3μV in the range of 0 ~ 50 ℃.
Disadvantages: The shortcomings of platinum-rhodium thermocouples are thermoelectric potential, the thermoelectric potential rate is small, the sensitivity reading is low, the mechanical strength decreases at high temperatures, and it is very sensitive to pollution. The precious metal materials are expensive, so the one-time investment is large.
The working principle of the platinum-rhodium thermocouple is that the platinum-rhodium thermocouple is formed by connecting two ends of two different conductors into a circuit. When the temperature of the two junctions is different, a 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 instrument will indicate the temperature value corresponding to the thermoelectric potential generated by the thermocouple.
Selection of platinum and rhodium thermocouples: when the measured temperature is normal at 1000 ~ 1300 ℃, it is recommended to use a single platinum rhodium thermocouple (platinum rhodium 10-platinum), when the measured temperature is normal at 1200 ~ 1600 ℃, it is recommended to use double platinum rhodium thermocouple ( Platinum-rhodium 30-platinum-rhodium6), so that the service life of platinum-rhodium thermocouples can be guaranteed within the temperature range used.
Pads for dogs,Dog cooling mat,Dog ice pack vest,Dog cooling sleep mat
Ningbo Hejia Ice pack co. LTD, , https://www.cooling-pack.com