There are many, many types of thermocouples but only a small number have been
standardized to the point of having distinct calibration tables, color codes and
assigned letter-designations that are recognized world wide. The ASTM
Standard E230 provides all the specifications for most of the common industrial
grades, including letter designation, color codes (USA only), suggested use limits
and the complete voltage versus temperature tables for cold junctions maintained
at 32 °F and 0 °C. Needless to say there are other thermocouple standards around
the world and the color codes can and do vary in places.
Note that there
are about three or four "classes"of thermocouples. Although no one
really calls them classes, they really are.
There are:
- The home
body class (called base metal),
- the upper crust class (called rare metal or
precious metal),
- the rarified class (refractory metals) and,
- the exotic
class (standards and developmental devices).
In most countires all but the
most exotic class are codified by a letter designation.
The home bodies, at
least in the USA, are the Types E, J, K, N and T.
The upper crust are: types
B, S, and R, platinum all to varying percentages .
The exotic class includes
several tungsten alloy thermocouples usually designated as Type W (something)
This page will grow as more net-based information on the subject expands and is
reviewed for inclusion here
