I.Accuracy of measurement and the choice of temperature measurement range
When Operation temperature is 1300~1800℃, and high precision be required,we choose type B thermocouple.When required accuracy is not high and the atmosphere allow, we can choose tungsten-rheniumthermocouple.So if the temperature above 1800℃,we normalliy chooseungsten-rhenium high temperature thermocouple. When Operation temperature is 1O00~1300℃, and high precision be required,we can choose type S and Type N thermocouple.Normally below 1000℃ we choose type K or type N thermocouples .Below 400℃,normally we choose type E .If temerature
below 250℃ or in the negative level,we choose type T thermocouple, as type T thermocouple operates stable and has high accuracy in the low temperature.
II. The choice of Atmosphere.
Type S,B,K thermocouples can suitable works in strong oxidation and weak reduction atmosphere. Type J and T thermocouples suitable for weak oxidation and reduction atmosphere. If we use protection tube which have better air tightness, the demand for atmosphere will be not strict.
III.The choice of durability and thermo-responsive.
The large diameter thermocouples normally have good durability, but thermo-responsive is slow, the thermocouples with big heat capacity also have slow thermo-responsive in the case of temperature is controlled, the temperature controling will be poor .If request fast thermo-responsive and good durability,the sheathed thermocouple is a good chioce.
IV. The nature and states of measured object choose the thermocouple
Motion object, vibration, high pressure vessel’s temperature measurement requires high mechanical strength, protecting tube is required if atmosphere has chemical pollution, and excellent insulation is required in the condition of electrical interference.
Selection process: model-type- anti-hazard classification- accuracy class- Install and fixed form- Protecting tube material-length or insertion depth.