Type J thermocouple wire, Fe-CuNi

Type J, Fe-CuNi thermocouple is a widely used thermocouple junction. In general, it is economically priced and it has a smaller temperature range compared to other thermocouple junctions: -210°C to +750°C. Type J thermocouples are favored for their low cost and high EMF, making them suitable for industrial applications.

These thermocouple wires feature iron-constantan conductors but have a slightly smaller temperature range compared to type K thermocouples and are not ideal for oxidizing environments. Caution is advised as the iron leg can rust if exposed to moisture.

In short;

Our standard type J wire items

ThermocoupleClassOutside Diameter in mmOn Stock
Type J wireClass 10.30 mm5 week delivery timeSend inquiry
Type J wireClass 10.80 mm5 week delivery timeSend inquiry
Type J wireClass 10.80 mmYesSend inquiry
Type J wireClass 11.00 mmYesSend inquiry
Type J wireClass 11.50 mm5 week delivery timeSend inquiry
Type J wireClass 12.00 mmYesSend inquiry
Type J wireClass 13.00 mm5 week delivery timeSend inquiry
Delivery times stated are for delivery to Kamet’s warehouse

Please contact us if you need different diameters. We can supply more custom made diameters (combinations) than stated above.

Operating temperature

Approximate working temperature tange;

  • Continues: +20 to +700°C
  • Short term: –180 to +750°C

Please note that these ranges are given as indicative values and vary per diameter.

Chemical composition

JP ( + )100
JN (-)4555

Physical properties

Density (g/cm3)7.868.90
Melting point (°C)15351210
Temp. coef. of resistance (x10-6/°C)500060
Linear expansion (coef. x10-6/°C)11.714
Thermal Conductivity (W m-1 °C-1 at 20°C)66.221.2

Environment and industrial usage

The type J thermocouple stands out for its affordability and efficiency in temperature monitoring of inert materials, vacuum applications, and hot processes including the manufacturing of plastics and resins. It is particularly effective in reducing atmospheres.

It exhibits resilience to aging, despite this, it is prone to rapid degradation in oxidizing atmospheres above 550°C. The thermocouple’s maximum sustainable operating temperature is approximately 800°C, but it can withstand up to 1000°C for brief durations. The minimum working temperature is set at -210°C; however, users should be cautious of condensation below ambient temperatures, which can lead to rusting of the iron component and low temperature embrittlement.

It should be noted that the accuracy of type J may be significantly compromised if used above 760°C, and its use is not advised in damp environments or for low temperature monitoring due to oxidation concerns.

JP/JN EMF reference table (mV)


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