TEMPCO TCWR-1003 Thermocouple Lead Wire
Wire,Thermocouple Lead - Type K, Fiberglass, Ambient Temp Limits 900 F, Wire Size Solid 2/20 AWG, Length 100 Ft, Color Code Yellow Positive/Red Negative, Jacket Color Brown
Wire that is used in a thermocouple from the point of sensing to the point of cold junction compensation (cjc end) where the signal is measured. A thermocouple is a sensor for measuring temperature, that consists of two dissimilar metals that are joined together at the sensing end. Different thermocouple types (e.g. J, K, T, E, etc) use different mixtures of metals in the wire.
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 insulation on thermocouple wire is color coded for identification.
Common guidelines include that the negative lead in insulated thermocouple wire is red.
The positive lead has the color of the thermocouple as well as the overall color of insulated extension grade wire. The outer jacket of thermocouple grade wire is typically brown.
For high temperature wire, it is common to have a color coded tracer thread in the white material. For information on usable temperature ranges for the insulation see the "Wire Insulation Identification" table. Other tables at this link are also available for information on the metals used in the thermocouple wire, insulation color codes, and more.