The characteristics and temperature measurement range of common thermocouple temperature sensors are as follows:
Type R thermocouple: Platinum-rhodium 13-platinum thermocouple, temperature range 0 ~ 1600℃. Advantages: good heat resistance, stability, reproducibility and superior accuracy; Good oxidation resistance and turbidity resistance; Can be used as a standard. Disadvantages: Small thermal electric potential; In the return element gas environment is more fragile (especially hydrogen, metal vapor); Compensation wire error is large; The price is high.
Type S thermocouple: platinum-rhodium 10-platinum thermocouple, temperature range 0 ~ 1600℃, old dividing size LB-3. Advantages: good heat resistance, stability, reproducibility and superior accuracy; Good oxidation resistance and turbidity resistance; Can be used as a standard. Disadvantages: small thermoelectric EMF value; In the regenerating gas environment is more fragile (especially hydrogen, metal vapor); Compensation wire error is large; The price is high.
Type K thermocouple: nickel-Chrome-nickel silicon thermocouple, nickel-Chrome-nickel aluminum thermocouple, temperature range -200 ~ 1300℃. Advantages: thermoelectric ELECTROmotive force has good linearity; Good oxidation resistance below 1000℃; Safety is good in metal thermocouple. Disadvantages: not applicable to the environment of reducing gases, especially carbon monoxide, sulfur dioxide, hydrogen sulfide and other gases; Compared with the precious metal thermocouple, the thermoelectric electromotive force changes greatly over time. Errors are caused by short range sorting.
Type B thermocouple: Platinum-rhodium 30-platinum-rhodium 6 thermocouple, temperature range 600 ~ 1800℃, old division number LL-2, free end in 0 ~ 50℃ without compensation wire. Advantages: applicable above 1000℃ to 1800℃; Thermoelectric emPs are very small at room temperature and do not need compensating wires. Good oxidation resistance and turbidity resistance; The heat resistance and mechanical strength are better than R type. Disadvantages: The thermoelectric EMF in medium and low temperature area is very small, the temperature under 600℃ is not accurate. Low thermoelectric EMFS; The straightness of thermoelectric EMFs is not good. The price is high.
N-type thermocouple: Nickel-Chrome-silicon -- nickel-silicon thermocouple, temperature range -270 ~ 1300℃. Advantages: thermoelectric ELECTROmotive force has good linearity; Good oxidation resistance under 1200℃; It is an improved type of K, which overcomes the deficiency of the thermoelectric EMF instability caused by the short-range lattice order of the Ni-Cr alloy between 300 ℃ and 500℃ and the thermoelectric EMF instability caused by the selective oxidation of the ni-Cr alloy around 800℃. Green Rot (high temperature corrosion) has little influence, and the heat resistance is higher than the K type. Disadvantages: not suitable for regenerating gas environment; Compared with precious metal thermocouple, thermoelectromotive force changes greatly over time.
Type E thermocouple: Nickel-Chromium-constantan thermocouple, temperature range -270 ~ 1000℃. Advantages: the most sensitive thermocouple in existence; Compared with J thermocouple, it has good heat resistance. The feet are not magnetic; Suitable for oxidizing gas environment; The price is low. Disadvantages: Not suitable for regenerating gas environment.
J type thermocouple: iron - constantan thermocouple, temperature range -210 ~ 1200℃. Advantages: It can be used in regenerating gas environment; The thermoelectric ELECTROmotive force is 20% larger than the K thermocouple. The price is cheaper, suitable for medium temperature area. Disadvantages: The positive pin end is easy to rust; Poor reproducibility.
T thermocouple: Copper-Constantan thermocouple, temperature range -270 ~ 400℃. Advantages: thermoelectric ELECTROmotive force has good linearity; Low temperature has good properties. Good reproducibility and high precision; Can be used in the environment of reducing element gas. Disadvantages: low temperature limit; The copper of positive pin is easy to oxidize; Heat conduction error is large.