Thermocouple Color Codes (ANSI and IEC)

Thermocouple extension wire is color coded by type. The US (ANSI) and international (IEC) standards use different colors, so check which one your wire follows.

ANSI (United States)

Type	Positive leg	Negative leg	Overall jacket
J	White	Red	Black
K	Yellow	Red	Yellow
T	Blue	Red	Blue
E	Purple	Red	Purple
N	Orange	Red	Orange
R / S	Black	Red	Green
B	Gray	Red	Gray

In the ANSI code the negative leg is always red.

IEC 60584-3 (international)

Type	Positive leg	Negative leg	Overall jacket
J	Black	White	Black
K	Green	White	Green
T	Brown	White	Brown
E	Violet	White	Violet
N	Pink	White	Pink
R / S	Orange	White	Orange
B	Gray	White	Gray

In the IEC code the negative leg is always white.

Practical notes

Never assume. Read the type printed on the jacket or the sensor tag. Confirm with a meter or the controller's configuration.
A reversed connection reads a temperature change in the wrong direction. If the reading falls when it should rise, check polarity first.
Extension wire must match the thermocouple type, and splices and terminals should use the same alloy or the correct compensating connector.
Type K and type N wires are often distinguished by the jacket color. Use the correct input type in the controller, because the wrong type gives a plausible but wrong reading.

Summary of ANSI/ASTM and IEC 60584-3 color codes for quick reference. Verify against the standard or the wire manufacturer's markings before wiring.