Thermocouple Reference Information

ANSI Type	Thermocouple Pair Materials	Polarity	Material Type	TC Temp. Range⁽³⁾	EMF (mV)
T	Copper Constantan®	+/-	Base	-200 to 350 °C	-5.60 to 17.82
J	Iron Constantan®	+/-	Base	0 to 750 °C	0 to 42.28
E	Chromel® Constantan®	+/-	Base	-200 to 900 °C	-8.82 to 68.78
K	Chromel® Alumel®	+/-	Base	-200 to 1250 °C	-5.97 to 50.63
R⁽¹⁾	Platinum 13% Rhodium Platinum	+/-	Noble	0 to 1450 °C	0 to 16.74
S⁽¹⁾	Platinum 10% Rhodium Platinum	+/-	Noble	0 to 1450 °C	0 to 14.97
C⁽¹⁾⁽²⁾	Tungsten 5% Rhenium Tungsten 26% Rhenium	+/-	Refractory	0 to 2320 °C	0 to 37.07

(1) Feedthroughs are offered in extension grade wire only. (Max. junction temp. 250°C.)
(2) Not ANSI Symbol.
(3) For Feedthrough Temperature Ratings, see general specifications in each section.

Thermocouple Environmental Limits (See Chart Below)

Copper-Constantan (T Curve)

The Copper-Constantan thermocouple, with a positive copper wire and a negative Constantan wire is recommended for use in mildly oxidizing and reducing atmospheres up to 400ºC. They are suitable for applications where moisture is present. This alloy is recom-mended for low temperature work since the homogeneity of the component wires can be maintained better than other base metal wires. Therefore, errors due to the non-homogeneity of wires in zones of temperature gradients is greatly reduced.

Iron-Constantan (J Curve)

The Iron-Constantan thermocouple with a positive iron wire and a negative Constantan wire is recommended for reducing atmospheres. The operating range for this alloy combination is 870ºC for the largest wire sizes. Smaller wire sizes should operate in correspondingly lower temperatures.

Chromel-Constantan (E Curve)

The Chromel-Constantan thermocouple may be used for temperatures up to 870ºC in a vacuum or inert, mildly oxidizing or reducing atmosphere. At sub-zero temperatures, the thermocouple is not subject to corrosion. This thermocouple has the highest emf output of any standard metallic thermocouple.

Chromel-Alumel (K Curve)

The Chromel-Alumel thermocouple, with a positive Chromel wire and a negative Alumel wire, is recommended for use in clean oxidizing atmospheres. The operating range for this alloy is 1260ºC for the largest wire sizes. Smaller wires should operate in correspondingly lower temperatures.

Platinum-Rhodium (S and R Curve)

Three types of noble-metal thermocouples are in common use. They are:

The S curve shows a positive wire of 90% platinum and 10% rhodium used with a negative wire of pure platinum,

The R curve indicates a positive wire of 87% platinum and 13% rhodium used with a negative wire of pure platinum, and

(not shown) a positive wire of 70% platinum and 30% rhodium used with a negative wire of 94% platinum and 6% rhodium.

They have a high resistance to oxidation and corrosion. However, hydrogen, carbon and many metal vapors can contaminate a platinum-rhodium thermocouple. The recommended operating range for the platinum-rhodium alloys is 1540ºC although temperatures as high as 1780ºC can be measured with the Pt-30% Rh vs Pt-6% Rh alloy combination.

Tungsten-Rhenium (C Curve)

Three types of tungsten-rhenium thermocouples are in common use for measuring temperatures up to 2760ºC. These alloys have inherently poor oxidation resistance and should be used in vacuum, hydrogen or inert atmospheres.

Temperature-vs-Voltage

17 Dec. 1999