Iron-Constantan (ANSI Symbol J)
The Iron-Constantan J curve thermocouple with a positive iron wire and a negative constantan wire is recommended for reducing atmospheres. The operating range for this alloy combination is 1600°F for the largest wires sizes. Smaller size wires should operate in correspondingly lower temperatures, Limit exposed junctions to 900°F continuous use.
Copper-Constantan (ANSI Symbol T)
The Copper-Constantan T curve thermocouple with a positive copper wire and a negative constantan wire is recommended for use in mildly oxidizing and reducing atmospheres up to 750°F. They are suitable for applications where moisture is present. This alloy is recommended for low temperature work since the homogeneity of the component wires can be maintained better than other base metal wires. Therefore, errors due to inhomogeneity of wires in zones of temperature gradient are greatly reduced. Limit exposed junctions to 500°F long term use.
Chromel-Alumel (ANSI Symbol K)
The Chrome-Alumel K curve 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 2300°F for the largest wire sizes. Smaller wire sizes should operate at correspondingly lower temperatures. The only suitable choice for exposed junctions from 1000°F to 1800°F.
Chromel-Constantan (ANSI Symbol E)
The Chromel-Constantan thermocouple may be used for temperatures up to 1600°F in a vacuum, 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. Limit exposed junctions to 1000°F continuous use.