Thermocouple Extension Wire Color Codes & Specifications

For United States, Canada & Mexico

See Also: TC Wire Color & Specs
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ANSI Code	ANSI Color Code	Positive (+) Lead	Negative (-) Lead	Temperature Range	Initial Calibration Tolerances
ANSI Code	ANSI Color Code	Positive (+) Lead	Negative (-) Lead	Temperature Range	Standard	Special
JX		Iron	Constantan (45% Nickel, 55% Copper)	32-392°F (0-200°C)	±2.2°C	±1.1°C
KX		Chromel^® (90% Nickel, 10% Chromium)	Alumel (95% Nickel, 2% Aluminum, 2% Manganese, 1% Silicon)	32-392°F (0-200°C)	±2.2°C	±1.1°C
EX		Chromel^® (90% Nickel,	Constantan (45% Nickel,	32-392°F (0-200°C)	±1.7°C	±1.1°C
TX		Copper	Constantan (45% Nickel,	32 to 212°F (0-100°C)	±1.0°C	±0.5°C
NX		Nicrosil (84.6% Nickel, 4% Chromium, 1.4 % Silicon)	Nisil (95.6% Nickel, 4.4 % Silicon)	32-392°F (0-200°C)	±2.2°C	±1.1°C
Compensating Extension Wire Type
RX*		Copper	Copper Alloy	32-392°F (0-200°C)	±9°F (±5°C)	N/A
SX*		Copper	Copper Alloy	32-392°F (0-200°C)	±9°F (±5°C)	N/A
BX*†		Copper	Copper	32 to 212°F (0-100°C)	+0°F (+0°C) –6.7°F (–3.7°C)	N/A

* Due to the non-linearity of the types R, S, and B temperature-emf curves, the error introduced into a thermocouple system by the compensating wire will be variable when expressed in degrees. The degree C tolerances are based on the following measuring junction temperatures.

Type Wire	Measuring Junction Temperature
SX	Greater than 1598°F (870°C)
BX	Greater than 1832°F (1000°C)

† Copper versus copper compensating extension wire, usable to 100°C (212°F) with maximum deviations as indicated, but with no significant deviation over 0°C to 50°C (32°F to 122°F) range.