Temperature measuring element - thermocouple
1, definition: temperature measuring instrument commonly used in the temperature measuring element, it directly measures the temperature, and the temperature
The signal is converted into a thermoelectric motive force signal and converted into the measured medium by an electrical instrument (secondary instrument)
temperature
2, principle: Two different components of the conductor combined into a closed loop, when there is a temperature gradient at both ends, the loop
An electromotive force is generated, a phenomenon called the thermoelectric effect, and this electromotive force is called the thermoelectric potential.
The end directly used to measure the temperature of the medium is called the working end (also known as the measuring end), and the other end is called
Cold end (also known as compensation end); The cold end is connected with the display instrument or supporting instrument, and the display instrument will indicate
The thermoelectric potential produced by a thermocouple.
3, electric couple classification:
• There are eight international regulations - B, R, S, K, N, E, J, T
• The measured temperature can be as low as minus 270 degrees Celsius and as high as 1800 degrees Celsius
• B, R, S - Platinum series of thermocouples, because platinum is a precious metal, but also
It's called a precious metal thermocouple
• The rest - cheap metal thermocouples
4, Muffle furnace thermocouple application
• 1000°C Muffle furnace
Type K thermocouple: Nickel-chromium-nickel-silicon thermocouple - the most widely used clean metal thermocouple
Operating temperature: -200~1300°C
1200°C-1400°C Muffle furnace
Type S thermocouple: Platinum rhodium 10-platinum thermocouple. Among them, rhodium is 10%, platinum is 90%, and the negative electrode (SN) is pure platinum, so it is commonly known as a single platinum rhodium thermocouple.
The long-term maximum operating temperature of the thermocouple is 1300℃, and the short-term maximum operating temperature is 1600℃.
• 1600°C- 1700°C Muffle furnace
Type B thermocouple: Platinum rhodium 30-platinum rhodium 6 thermocouple, double platinum rhodium precious metal thermocouple
Operating temperature: minimum 0°C, long-term maximum 1600°C, short-term maximum 1800°C
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