Household thermometer: - temperature range 30 - 100 ℃ temperature range small cheap platinum-rhodium thermocouple is also called the high-temperature thermocouple, precious metals platinum rhodium have single platinum rhodium ( Platinum rhodium - 10 Platinum rhodium) And double platinum rhodium ( Platinum rhodium - 30 Platinum rhodium (6) , them as temperature measurement sensor, usually with temperature transmitter, controller and display instrument, such as process control system, to directly measure or control in the production of a variety of 0 Fluid over a range of 1800 ℃, steam and gas medium and solid surface temperature. Platinum rhodium thermocouple for precious metals thermocouple. Accidentally wire diameter provision of 0. 5 mm, allowable deviation - 0. The positive (015 mm, 英国石油公司(BP) In the name of the chemical composition of platinum rhodium, contain the rhodium is 30%, platinum-based is 70%, the cathode ( BN） For platinum rhodium, rhodium for content 6%, therefore, commonly known as the dual platinum-rhodium thermocouple. The temperature is 1600 ℃, the long-term use of thermocouple short-term use temperature is 1800 ℃. Advantages of platinum-rhodium thermocouple in the thermocouple series has high accuracy, good stability, test your area wide, long service life, high temperature limit, etc. Suitable for oxidation and inert atmosphere, can also be short term used in vacuum, but does not apply to reducing atmosphere or containing metal or nonmetal steam atmosphere. 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. Faults platinum-rhodium thermocouple deficiency is thermoelectric potential, thermoelectric potential rate of small, low sensitivity and mechanical strength under high temperature to drop, is sensitive to pollution, precious metal materials is expensive, and one-time investment is larger. The working principle of platinum-rhodium thermocouple is platinum rhodium thermocouple is composed of two different components of two ends synthesis loop conductor, not at the same time, when the two junction temperature will produce thermal current in the circuit. If the work end of the thermocouple with the reference when there is a difference in temperature, display instrument will be installed by the thermocouple thermoelectric potential of the corresponding temperature value. The choice of platinum-rhodium thermocouple measuring temperature is normal during 1000 ~ 1300 ℃ is recommended to use the single platinum-rhodium thermocouple ( Platinum rhodium - 10 Platinum) , measuring the temperature of the normal during 1200 ~ 1600 ℃ suggest using double platinum rhodium thermocouple ( Platinum rhodium - 30 Platinum rhodium (6) So are using temperature range can ensure the service life of platinum-rhodium thermocouple.