J-type thermocouple materials and characteristics

    J-type thermocouple, namely iron-copper-nickel thermocouple, also known as iron-constantan thermocouple, is also a kind of low-cost metal thermocouple. Its positive electrode (JP) has a nominal chemical composition of 99.95% pure iron, and the negative electrode (JN) is a copper-nickel alloy, often called constantan (55% copper-45% nickel). The coverage measurement temperature range of the iron-constantan thermocouple is -200~1200℃, but the commonly used temperature range is 0~750℃. The thermoelectric potential of J-type thermocouple is 5.268mV at 100℃.

     The J-type thermocouple is cheap, and the thermoelectromotive force rate is larger than that of the K-type. It can be used in both oxidizing and reducing atmospheres, and it is resistant to H2 and CO corrosion. When the temperature exceeds 538°C, the iron oxidizes quickly, and the temperature resistance is not high enough to be used in high temperature areas.

     J-type thermocouples can be used in vacuum, oxidation, reduction and inert atmospheres, but the positive electrode iron oxidizes faster at high temperatures, so the use temperature is limited, and it cannot be used directly and unprotected in a vulcanizing atmosphere at high temperatures. It is not recommended to use at low temperatures.

(Huiputech)