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, %
Specification (IEC60584-1)
| TYPE | EMF Versus Pt.67(mV) |
| 100℃ | 200℃ | 300℃ | 400℃ | 600℃ |
| JP-JN | 5.207-5.331 | 10.717-10.841 | 16.244-16.410 | 21.760-21.936 | 32.956-33.236 |
Physical and Mechanical Properties (RT, Annealed)
| Type | Density, g/cm³ | Melting Point, ℃ | Tensile Strength, MPa | Elongation, % | Resistivity, μΩ.m |
| JP | 7.8 | 1407 | ≥240 | ≥20 | 0.12 |
| JN | 8.8 | 1220 | ≥390 | ≥25 | 0.49 |
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℃.
