Thermocouple Types | What is the difference btw. Type K & Type J? (2025)


In the following table you can see an overview of different types ofthermocouples with general properties, the temperature range, material composition as well as advantages and areas of application. Information on the electrical voltage of thermocouples can be found in the table Thermoelectric voltage.

Thermocouple- types
--------------
Colour-
code

Characteristics of Thermocouples

General

Composition

Temperature range

Suitable application

Unsuitable application

Type E

base metal thermocouple

NiCr -CuNi
(nickel-chrome/copper-nickel)

single wires made of non precious metals

Type E (+) leg:
89-90% nickel, 9-9.5% chrome, 0.5% silicium and iron balance: C, Mn, Nb, Co

Type E (-) leg:
55% copper, 45% nickel approx. 0.1%, co balt, iron and manganese

-200°C/+700°C

  • in pure, oxidizing (air), or neutral atmosphere (inert gases)

  • high resistance against corrosion

  • small thermal conductivit

  • not sulphuric, reducing or alternately oxidizing, and reducing atmosphereu

  • do not apply in vacuum for a long time

Type J

base metal thermocouple

Fe - CuNi
(iron/copper-nickel)

single wires made of non precious metals

Type J (+) leg:
99.5 % iron, approx. 0.25 % manganese, approx. 0.12 % copper, balance: other impurities

Type J (-) leg:
55% copper, 45% nickel approx. 0.1%, cobalt, iron, and manganese

-180°C/+700°C

  • from 0 to 760°C in vacuum, oxidizing (air), reducing orinert atmosphere (inert gases)

  • temperatures below 0°C

  • sulphurous atmosphere above +500°C

  • above 760°C only with bigger wire diameters

Type K

base thermocouple

NiCr-Ni
(nickel-chrome/ nickel-aluminium)

single wires made of non precious metals

Type K (+) leg:
89-90% nickel, 9-9.5% chrome, 0.5 % silicium and iron balance: C, Mn, Nb, Co

Type K (-) leg:
95-96% nickel, 1-1.5% silicium, 1-2.3 % aluminium, 1-3.2% manganese, 0.5% cobalt, balance: Fe, Cu, Pb

-270°C/+1372°C

  • from 250°C to 1260°C in pure, oxidizing (air) and neutralatmosphere (inert gases)

  • for higher temperatures bigger wire diameters are recommended

  • between 250°C up to 600°C not suitable for exact measurements with quick temperature changes

  • not appropriate for a longer time with high temperatures in vacuum

  • do not apply with high temperatures in sulfurous, reducingor alternately oxidizing, and reducing atmoshere without protection

  • do not use in atmosphere favourizing "green mould"

Type L

base thermocouple

Fe - CuNi
(iron/copper-nickel)

single wires made of non precious metals

Type L (+) leg:
99.5 % iron, approx. 0.25 % manganese, approx. 0.12 % copper, ballance: other impurities

Type L (-) leg:
55% copper, 45% nickel, approx. 0.1% cobalt, iron, and manganese

0°C/+900°C

  • from 0°C to 760°C in vacuum, oxidizing (air), reducing or inert atmosphere (inert gases)

  • above 500°C bigger wire diameters are recommended

  • Temperatures below 0°C

  • sulphurous atmosphere above +500°C

  • above 760°C only with bigger wire diameters

Type N

base thermocouple

NiCrSi - NiSi
(nickel-chrome-silicium/nickel-silicium-magnesium)

single wires made of non precious metals

Type N (+) leg:
84% nickel, 14-14.4 % chrome, 1.3-1.6% silicium, ballance (not more than 0.1%): Mn, Fe, C, Co

Type N (-) leg:
95 % nickel, 4.2-4.6 % silicium, 0.5-1.5 % magnesium, ballance: Fe, Co, Mn, C,
(altogether 0.1-0.3%

-270°C/+1300°C

  • from 300°C to 1260°C in pure, oxidizing (air) and neutral atmosphere (inert gases)

  • do not use with high temperatures in sulphurous, reducing or alternately oxidizing, and reducing atmosphere without protection

  • do not use with high temperatures in vacuum

  • do not use in atmosphere faviourizing "green mould"

  • reducing atmosphere

Type R

base thermocouple

Pt13%Rh - Pt
(platinum 13% rhodium/ platinum)

single wires made of platinum and platinum - rhodium alloy

Type R (+) leg:
platinum with 99.99% purity with a rhodium alloy (purity 99.98%) 13±0.05% rhodium portion

Type R (-) leg:
platinum with 99.99% purity

-50°C/+1768.1°C
(melting point) recommended:
up to +1300°C

  • pure, oxidizing atmosphere (air), non aggresive (inert-) gases, and short-term in vacuum

  • above +1200°C type B more appropriate

  • reducing atmosphere umetal gases (for example plomb or zinc)

  • agressive vapours containing arsenic, phosphor or sulphur

  • do never use metal protecting tubes with higher temperatures

  • sensitive against impurities of impure metals

Type S

base thermocouple

Pt10%Rh - Pt
(platinum 10% Rhodium/ platinum)

single wires made of platinum and platinum - rhodium alloy

Type S (+) leg:
platinum with 99.99% purity with a rhodium alloy (purity 99.98%) 10±0.05% rhodium portion

Type S (-) leg:
platinum with 99.99% purity

-50°C/+1768.1°C
(melting point) recommended:
up to +1300°C

  • pure, oxidizing atmospheres (air), non agressive (inert-) gases, and short-term in vacuum

  • above +1200°C type B more appropriate

  • reducing atmosphere umetal gases (for example plomb or zinc)

  • agressive vapours containing arsenic, phosphor, or sulphur

  • do never use metal protecting tubes with higher temperatures

  • sensitive against impurities of impure metals

Type B

base thermocouple

Pt 30%Rh - Pt 6%Rh (platinum -0% rhodium/ platinum-6% rhodium)

single wires made of platinum and platinum - rhodium alloy

Type B (+) leg:
platinum with 99.99% purity with a rhodium alloy (purity 99.98%) 29.60±0.2% rhodium portion

Type B (-) leg:
platinum with 99.99% purity with a rhodium alloy (purity 99.98%) 6.12±0.02% rhodium portion

max. +1820°C
(melting point) ordinary up to
+1700°C

  • pure, oxidizing atmosphers

  • neutral atmospheres

  • vacuum

  • reducing atmosphere or such with agressive vapoursor impurities which react with metals of the platinum group, if it is not protected with a non metal protecting tube

Type T

base thermocouple

Cu - CuNi
(copper/copper-nickel)

single wires made of non precious metals

Type T (+) leg:
99.95% copper, 0.02-0.07% oxygen, 0.01% impurities

Type T (-) leg:
55% copper, 45% nickelapprox. 0.1% cobalt, iron, and manganese

-270°C/+400°C

  • from -200°C to 370°C in vacuum, oxidizing (air), reducing or inert atmosphere (inert gases)

  • with higher temperatures bigger wire diameters are recommended

  • above +370°C not appropriate in a hydrogen atmosphere

  • not appropriate in radioactive environment

Type U

Unedelmetall-base thermocouple

Cu - CuNi (copper/copper-nickel)

single wires made of non precious metals

Type U (+) leg:
99.95% copper, 0.02-0.07% oxygen, 0.01% impurities

Type U (-) leg:
55% copper, 45% nickel approx. 0.1% cobalt, iron, and manganese

0°C/+600°C
(+400°C)

  • from -200°C to 370°C in vacuum, oxidizing (air), reducing or inert atmosphere (inert gases)

  • with higher temperatures bigger wire diameters are recommended

  • above +370°C not appropriate in a hydrogen atmosphere

  • not appropriate in radioactive environment

Thermocouple Types | What is the difference btw. Type K & Type J? (2025)
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