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Common thermocouple model specifications

2022-02-26 14:58:18
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1, K type thermocouple nickel chrome (nickel silicon (nickel aluminum) thermocouple type K thermocouple is oxidation resistance strong base metal thermocouple, measurable 0 ~ 1300 ℃ medium temperature, suitable for applied successively in the oxidizing and lazy gas, short-term using temperature is 1200 ℃, long using temperature is 1000 ℃, its approximate linear contact temperature of thermoelectric potential, Is the current use of large thermocouple. However, it is not suitable for bare wire application in vacuum, sulfur, carbon and REDOX atmosphere; When the oxygen partial pressure is low, the chromium in the nickel chromium electrode will be preferentially oxidized, so that the thermoelectric potential has a great change, but the metal gas has little influence on it, so the metal maintenance pipe is mostly used.


Disadvantages of type K thermocouple:


(1) Thermoelectric potential is less stable at high temperature than N-type thermocouple and precious metal thermocouple, and is often damaged by oxidation at higher temperatures (such as more than 1000℃);


(2) In the scale of 250 ~ 500℃, the short-term thermal cycle stability is not good, that is, at the same temperature point, in the process of heating and cooling, the thermoelectric potential values are different, the difference can reach 2 ~ 3℃;

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(3) the negative pole in the scale of 150 ~ 200℃ to produce magnetic transformation, resulting in the scale of temperature to 230℃ in the scale of the indexing value often violates the indexing table, especially in the magnetic field is often used and time independent thermoelectric potential interference;


(4) In the high-flux system irradiation environment for a long time, due to the decay of manganese (Mn), cobalt (Co) and other elements in the negative electrode, its stability is poor, resulting in a great change in thermoelectric potential.


2, TYPE S thermocouple (platinum-rhodium 10-platinum thermocouple) The thermocouple is composed of 10% platinum-rhodium alloy with rhodium as the positive pole, and pure platinum as the negative pole.


Its characteristics are:


(1) Thermoelectric function is stable, oxidation resistance is strong, suitable for continuous use in oxidizing atmosphere, long time use temperature can reach 1300℃, up to 1400℃, even in the air, pure platinum wire will recrystallization, make the grain coarse and cracking;


(2) High accuracy, accuracy grade in all thermocouples, usually used for specification or measurement of higher temperatures;


(3) Wide application scale, good uniformity and interchangeability;


(4) The main disadvantages are: small differential thermoelectric potential, so low sensitivity; More expensive, low mechanical strength, not suitable for use in reducing atmosphere or metal steam conditions.


3, E type thermocouple (nickel-chromium - copper nickel [Constantan] thermocouple)E type thermocouple is a relatively new product, positive nickel-chromium alloy, negative nickel-copper alloy (constantan).


Its big characteristic is in commonly used thermocouple, its thermoelectric potential is large, that is, high sensitivity; Its application scale is not as wide as k-type couple, but it is often selected under the condition of high sensitivity, low thermal conductivity and large resistance. The constraint conditions in use are the same as K type, but it is not sensitive to corrosion in the atmosphere with high humidity.


4, N type thermocouple (nickel chrome - nickel silicon silicon thermocouple) the main characteristics of the thermocouple: under 1300 ℃ temperature anti-oxidation ability, stability and short-term thermal cycle for a long time good reproducibility, good resistance to radiation and low temperature function, in addition, within the scale of 400 ~ 1300 ℃, the thermoelectric properties of N type thermocouple linear better than K type I; But in the low temperature scale (-200 ~ 400℃) nonlinear error is large, together, the material is hard difficult to process.


5, J type thermocouple (Fe-Constantan thermocouple)J type thermocouple: The thermocouple is extremely pure iron, the negative is extremely constantan (copper and nickel alloy), the characteristic is cheap price, is suitable for vacuum, oxidation reduction or languid atmosphere temperature scale from 200 ~ 800 ℃, but the commonly used temperature under 500 ℃, due to more than the temperature, the oxidation rate of iron hot electrode acceleration, if use coarse wire diameter wire, Can be used in high temperature and has a long life; The thermocouple can corrode hydrogen (H2) and carbon monoxide (CO) gases, but cannot be used at high temperatures (e.g. 500℃) in an atmosphere containing sulfur (S).


6, T type thermocouple (copper - copper nickel thermocouple)T type thermocouple: the thermocouple is very pure copper, negative is very copper nickel alloy (also known as copper), its main characteristics are: in base metal thermocouple, its accuracy, good uniformity of the thermal electrode; It is the use of temperature - 200 ~ 350 ℃, due to the copper thermoelectric extremely easy oxidation, and the oxide film falls off easily, so use in oxidizing atmosphere, generally should not exceed 300 ℃, inside - 200 ~ 300 ℃, their sensitivity is higher, copper-constantan thermocouple and a characteristic is cheap price, is one of the commonly used several kinds of stereotypes products cheap.


7, R type thermocouple (platinum-rhodium 13-platinum thermocouple) the thermocouple is positive containing 13% of platinum-rhodium alloy, negative is pure platinum, compared with S type, its potential rate is about 15%, other functions are almost the same, this kind of thermocouple in The Japanese industry, as a high temperature thermocouple, and in China, is used less.


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Company: Zhejiang Chunhui Instrument Co., LTD

Address: 101 Mingyue Road, Shangyu District, Shaoxing City, Zhejiang Province