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Type J Thermocouple - Technical Information

Type J - Iron vs Copper-Nickel, IEC 60584-1

Thermocouple Type J, commonly referred to as Iron/Constantan, this is one of the few thermocouples that can be used safely in reducing atmospheres. However, in oxidising atmospheres above 550°C, degradation is rapid. Maximum continuous operating temperature is around 800°C, although for short term use, temperatures up to 1,000°C can be handled. Minimum temperature is -210°C, but beware of condensation at temperatures below ambient - rusting of the iron arm can result, as well as low temperature embrittlement.

Type J Thermocouples - Typical Constructions and Styles

Type J Mineral Insulated
Thermocouples Type J Thermocouples with Mineral Insulation

Rugged sensors, ideal for most applications. Vast choice of terminations e.g. pot seals, cables, connectors, heads etc.Type J Swaged Tip
Thermocouples Type J Thermocouples with Swaged Tip

Fast response thermocouples ideal for industrial and other applications. Type J Miniature
Thermocouples Miniature Type J Thermocouples

Ideal for precision temperature measurements where minimal displacement and a fast response is required. Type J Heavy Duty
Thermocouples Heavy Duty Type J Thermocouples

For industrial applications such as furnaces, kilns, ovens, boliers, flues etc. Many types of sheath material available. General Purpose
Type J Thermocouples General use Type J Thermocouples

A wide range of thermocouples to suit many applications. Hand held, surface, bayonet, bolt, patch styles etc. ATEX/IECEx Approved
Type J Thermocouples ATEX Approved Type J Thermocouples

A large range of thermocouples with a variety of terminations such as pot seal, terminal heads etc.

Type J - Technical Data

Conductor Combination		Approximate generated EMF change in µV per ºC change (referenced to 0ºC) at:			Approximate Working Temperature Range		Thermocouple Output Tolerances to IEC 60584-1
+ Leg	- Leg	100ºC	500ºC	1000ºC	Continuous	Short Term	Type	Class 1	Class 2	Class 3
IRON (magnetic) Also known as: Fe	COPPER - NICKEL Also known as: Nickel-Copper, Constantan, Advance™, Cupron™	54	56	59	+20 to +700°C	–180 to +750°C	Temperature Range Tolerance Value Temperature Range Tolerance Value	–40°C to +375°C ±1.5°C 375°C to 750°C ±0.004⋅ \|t\|	–40°C to +333°C ±2.5°C 333°C to 750°C ±0.0075 ⋅ \|t\|	N/A

1. The tolerance is expressed either as a deviation in degrees Celsius or as a function of the actual temperature.
2. Thermocouple materials are normally supplied to meet the tolerances specified in the table for temperatures above –40 deg C. These materials however, may not fall within the tolerances for low temperatures given under Class 3 for Types T, E and K thermocouples. If thermocouples are required to meet limits of Class 3, as well as those of Class 1 and/or Class 2, the purchaser should state this, as selection of materials is usually required.
3. The maximum temperature rating is dependant upon construction, size and atmospheric conditions. A more detailed guide for the maximum temperature ratings of mineral insulated thermocouples can be found here.

J Type Cable Colour Codes for Thermocouples

International Colour Code to IEC 60584-3	ANSI MC96.1	Redundant national colour coding for thermocouple cables
International Colour Code to IEC 60584-3	ANSI MC96.1	BS 1843	DIN 43714	NFC 42324

Free Guide to Thermocouple and Resistance Thermometry

Frequently Asked Questions

What is a thermocouple and how does it work?
A thermocouple is a type of temperature sensor that generates a voltage when two different metals are joined at one end and exposed to a temperature difference between the "hot" junction (where the temperature is measured) and the "cold" junction (the reference point). This voltage is then measured to determine the temperature at the hot junction.
How do I choose the right thermocouple for my application?
The ideal thermocouple depends on factors such as temperature range, accuracy, termination type, mounting requirements and environmental conditions. We offer a variety of thermocouples with different sheath materials, constructions, terminations, and temperature ratings to meet your needs. If you need specific advice, our engineers are happy to assist!
What is the maximum temperature rating of your thermocouples?
Our thermocouples are designed to handle a wide range of temperatures with some mineral insulated thermocouples able to withstand temperatures up to 1400ºC and ceramic sheathed thermocouples going even higher to 1600ºC. Each product listing includes the maximum temperature rating, so you can choose the best thermocouple for your application.