Thermocouples are used in industrial applications for temperature measurements on gas turbine exhaust, diesel engines, kilns or other industrial processes that require the measurement of a temperature. The cables consist of two solid or stranded dissimilar metal alloys for conductors, that produce a voltage when heated. Different alloys are used for different temperature ranges. Specific alloys that have a repeatabe relationship between temperature and voltage.The most common thermocouple cables used are extension grade, solid conductor, KX and JX. Other alloys, for more specialized applications, are also available.
The thermocouple cable goes from the point of sensing to the point of cold junction compensation (cjc end) where the signal is measured. At the cjc end, the millivolt value provided by the thermocouple represents the difference in temperature of the sensing end as compared to the cjc end (also called the reference end).
The cable conductors and outer jacket are color coded to the ANSI MC96.1 standard (other options are available). Available in both a CSA tray and armored version, these cables can be used in many industrial applications.
The main limitation with thermocouples is accuracy; system errors of less than one degree Celsius (°C) can be difficult to achieve.