The Characteristics Of Different Types Of Thermocouples
Below we briefly introduce the characteristics of several common thermocouples.
E-type thermocouple (nickel-chromium-copper-nickel [constantan] thermocouple) E-type thermocouple is a relatively new product, the positive electrode is nickel-chromium alloy, and the negative electrode is copper-nickel alloy (constantan). Its biggest feature is that among the commonly used thermocouples, its thermoelectric potential is the highest, that is, the highest sensitivity; although its application range is not as wide as the K-type couple, but under the conditions that require high sensitivity, low thermal conductivity, and allowable large resistance, It is often selected; the restrictions in use are the same as the K-type, but it is not very sensitive to corrosion in an atmosphere containing a higher humidity.
N-type thermocouple (Ni-Cr-Si-Ni-Si thermocouple) The main features of this thermocouple: strong anti-oxidation ability under 1300℃, long-term stability and short-term thermal cycle reproducibility, resistance to nuclear radiation and low temperature The performance is good. In addition, the linearity of the thermoelectric characteristics of the N-type thermocouple is better than that of the K-type in the range of 400～1300℃; but in the low temperature range (-200～400℃), the nonlinear error is larger. At the same time, the material Harder and difficult to process.
J-type thermocouple (iron-constantan thermocouple) J-type thermocouple: The positive electrode of this thermocouple is pure iron, and the negative electrode is constantan (copper-nickel alloy). It is characterized by low price and suitable for vacuum oxidation reduction or inertness In the atmosphere, the temperature range is -200～800℃, but the commonly used temperature is only below 500℃, because after this temperature, the oxidation rate of the iron hot electrode will increase. If the wire with thick wire diameter is used, it can still be used at high temperature. And has a long life; the thermocouple can withstand hydrogen (H2) and carbon monoxide (CO) gas corrosion, but can not be used in high temperature (for example, 500 ℃) sulfur (S) atmosphere.
T-type thermocouple (copper-copper-nickel thermocouple) T-type thermocouple: The positive electrode of this thermocouple is pure copper, and the negative electrode is copper-nickel alloy (also called constantan). Its main characteristics are: in the base metal thermocouple , It has the highest accuracy and good uniformity of the hot electrode; its use temperature is -200～350℃, because copper hot electrode is easy to oxidize, and the oxide film is easy to fall off, so when used in an oxidizing atmosphere, it should not exceed At 300℃, in the range of -200～300℃, their sensitivity is relatively high. Another feature of copper-constantan thermocouples is that they are cheap, and they are the cheapest of several commonly used stereotypes.
R-type thermocouple (platinum rhodium 13-platinum thermocouple) The positive electrode of this thermocouple is a platinum-rhodium alloy containing 13%, and the negative electrode is pure platinum. Compared with the S-type, its electric potential rate is about 15% higher, and other properties are almost Similarly, this type of thermocouple is used most often as a high-temperature thermocouple in the Japanese industry, while it is used less in China.
So you need to choose the product that suits their needs when buying.
