Thermocouple accuracy and temperature measurement range selection
Thermocouple accuracy and temperature measurement range selection
Two different materials of conductors or semiconductors A and B are welded together to form a closed loop. When there is a temperature difference between the two dedicated points 1 and 2 of conductors A and B, an electromotive force is generated between them, resulting in a magnitude of current in the loop, which is called a thermoelectric effect. Thermocouple is the use of this effect to work.
Select the thermocouple to be based on the use of temperature range, the required accuracy, the use of the atmosphere, the determination of the performance of the object, response time and economic benefits and other comprehensive consideration.
1, the measurement accuracy and temperature measurement range of choice The use of temperature in the 1300 ~ 1800 ℃, the required accuracy is relatively high, the general use of B-type thermocouple; require accuracy is not high, the atmosphere allows the use of tungsten rhenium thermocouple, higher than 1800 ℃ The use of tungsten rhenium thermocouple; the use of temperature in the 1000 ~ 1300 ℃ requirements and relatively high accuracy S-type thermocouple and N-type thermocouple; 1000 ℃ below the general use of K-type thermocouple and N-type thermocouple, less than 400 ℃ General use E-type thermocouple; 250 ℃ and negative temperature measurement is generally used T-type galvanic, low temperature T-type thermocouple stability and high accuracy.
2, the use of the choice of the atmosphere S-type, B-type, K-type thermocouple suitable for strong oxidation and weak use of the atmosphere, J-type and T-type thermocouple suitable for weak oxidation and reducing the atmosphere, if the use of air tightness comparison Good protection tube, the requirements of the atmosphere is not too strict.
3, the choice of durability and thermal response diameter of the thermocouple durability is good, but the response is slower, for the heat capacity of the thermocouple, the response is slow, measuring the gradient of the temperature, in the case of temperature control , Temperature difference. Requires a fast response time and requires a certain degree of durability, choose armor even more appropriate.
4, the nature of the object and the state of the choice of thermocouple
Moving objects, vibration objects, high pressure vessel temperature requirements of high mechanical strength, chemical pollution, the atmosphere requires a protective tube, electrical interference in the case of higher insulation requirements
