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The graduation of thermocouple temperature sensor and the advantages and disadvantages of various standardized thermocouples

Published on: December 19, 2018 by Zetian sensing

There are several kinds of temperature sensors, such as J, R, t, K, etc. S, R and B belong to noble metal thermocouple, and N, K, e, J, t belong to low metal thermocouple.

S grade is characterized by strong oxidation resistance, which is suitable for continuous use in oxidizing and inert atmosphere. The long-term service temperature is 1400 ℃ and the short-term service temperature is 1600 ℃. Among all the thermocouples, the s graduation has the highest accuracy level and is usually used as a standard thermocouple;

Compared with s graduation, R graduation has almost the same performance except thermoelectric EMF which is about 15% larger;

The thermal electromotive force of B scale is very small at room temperature, so it is not necessary to compensate the wire in the measurement. Its long-term use temperature is 1600 ℃, short-term 1800 ℃. It can be used in oxidizing or neutral atmosphere or short-term in vacuum.

The characteristics of N-scale are strong oxidation resistance at high temperature at 1300 ℃, good long-term stability of thermoelectric EMF and reproducibility of short-term thermal cycle, good resistance to nuclear radiation and low temperature, which can partly replace s-grade thermocouple;

It is suitable for continuous use in oxidizing and inert atmosphere. The long-term service temperature is 1000 ℃ and the short-term service temperature is 1200 ℃. It is the most widely used thermocouple;

The characteristic of e graduation mark is that the thermoelectric EMF of thermocouple is the largest, that is, the sensitivity is the highest. It should be used continuously in oxidizing and inert atmosphere at 0-800 ℃;

The characteristic of J grade is that it can be used not only in oxidizing atmosphere (the upper limit of service temperature is 750 ℃), but also in reducing atmosphere (the upper limit of service temperature is 950 ℃), and it is resistant to the corrosion of H2 and co gases, which is mostly used in oil refining and chemical industry;

The characteristic of the t-scale is the highest accuracy level among all low-cost metal thermocouples, and is usually used to measure temperatures below 300 ℃.

 Standard thermocouple

The following table shows the various standardization Thermocouple temperature sensor Comparison of advantages and disadvantages of

Thermocouple type advantage shortcoming
B ① It is suitable for measuring high temperature above 1000 ℃. ② the thermoelectromotive force is very small at room temperature, so it is not necessary to compensate the conductor ③ oxidation resistance and chemical corrosion resistance ① In the field of medium and low temperature, the thermoelectric EMF is small and can not be used below 600 ℃. (2) low sensitivity (3) poor linearity of thermoelectric EMF (4) high price
R.S ① High precision, good stability, not easy to deteriorate ; (2) oxidation resistance, chemical corrosion resistance (3) can be used as the standard ① Low sensitivity (2) not suitable for reducing atmosphere (especially H2, metal vapor) (3) poor linearity of thermoelectric EMF (4) high price
N ① The linear thermoelectric EMF is good (2) the oxidation resistance is good below 1200 ℃ (3) the short-range ordered structure has little effect ① It is not suitable for reducing atmosphere. ② compared with precious metal thermocouple, aging changes greatly
K ① The linear thermoelectric EMF is good ② the oxidation resistance is good below 1000 ℃; ③ the stability is better in the low metal thermocouple ① It is not suitable for reducing atmosphere 2. The aging change is large compared with the noble metal thermocouple ; 3. The error is caused by the change of short-range ordered structure
E ① Among the existing thermocouples, the sensitivity is the highest. ② compared with J-type thermocouples, the thermal resistance is good. ③ the two poles are non-magnetic ① It is not suitable for low thermal conductivity
J ① It can be used in reductive atmosphere. ② the thermoelectric EMF is about 20% higher than that of K-type ① Iron positive electrode is easy to rust ; (2) thermoelectric characteristics drift greatly
T ① Good linearity of thermoelectric EMF ② good low temperature characteristics ; ③ good quality stability of products ; ④ it can be used in reducing atmosphere Low temperature ; (2) copper positive electrode is easy to oxidize ; (3) large error of heat conduction

This article originates from Zetian sensing Please keep the source.