Type J (Iron/Constantan)

Type J is the oldest thermocouple and has a large installed base. It has a good range up to 760°C. One leg is Iron and is subject to corrosion in moist or Oxygen atmospheres. It can be used in Reducing, Vacuum and Inert atmospheres.

Chemical Composition, %

TypeFeCuNi
JP100
JN5545

Specification (IEC60584-1)

TYPEEMF Versus Pt.67(mV)
100℃200℃300℃400℃600℃
JP-JN5.207-5.33110.717-10.84116.244-16.41021.760-21.93632.956-33.236

Physical and Mechanical Properties (RT, Annealed)

TypeDensity, g/cm³Melting Point, ℃Tensile Strength, MPaElongation, %Resistivity, μΩ.m
JP7.81407≥240≥200.12
JN8.81220≥390≥250.49

Features

  • Good resistance to oxidation
  • High EMF output against Platinum 67
  • Good temperature accuracy, sensitivity and stability

Applications

Type J Thermocouple is recommended for vacuum, oxidizing, reducing or inert atmosphere, but it can’t be used in sulphurous atmosphere above 500℃.