Fe- CuNi thermocouple (type J) is also named Iron-Constantan thermocouple.. It is used in vacuum, oxidizing, inert or reducing atmospheres. Iron element oxidizes rapidly at temperatures exceeding 538'C, and therefore heavier gauge wire is recommended for longer life at these temperatures.
Type J thermocouple has good resistance to oxidation and high EMF output against Platinum 67, with good temperature accuracy, sensitivity and stability. It is recommended for vacuum, oxidizing, reducing or inert atmospheres, but it can not be used in sulphurous atmosphere above 500℃.
Type J chemical composition:
Positive leg Fe (JP) is Pure Iron; negative leg Constantan (JN) isCu: Ni≈ 55%: 45%
Type J Temperature Range:
Thermocouple grade wire, 0~750 ℃(for short term) and 0~600℃( for long term)