Thermocouple wire color codes: IEC and ANSI
Conductor and jacket colors of K, J, T, E, N, R, S and B thermocouples in the IEC 60584-3 and ANSI MC96.1 codes, and how to confirm the type in the field.
The color of the conductors and the cable jacket shows the thermocouple type and the polarity. There are two main codes: the international IEC 60584-3 and the American ANSI/ASTM MC96.1. They use different colors for the same type.
| Type | IEC + | IEC − | IEC jacket | ANSI + | ANSI − | ANSI extension jacket |
|---|---|---|---|---|---|---|
| J | Black | White | Black | White | Red | Black |
| K | Green | White | Green | Yellow | Red | Yellow |
| T | Brown | White | Brown | Blue | Red | Blue |
| E | Violet | White | Violet | Violet | Red | Violet |
| N | Pink | White | Pink | Orange | Red | Orange |
| R | Orange | White | Orange | Black | Red | Green |
| S | Orange | White | Orange | Black | Red | Green |
| B | — | — | — | Gray | Red | Gray |
Type B in the IEC code: the colors are not defined in the reference used here. Confirm the cable with the supplier documentation.
Quick rules
- IEC: the negative is always white, and the jacket has the color of the positive.
- ANSI: the negative is always red. Watch out: in the American code, red is the negative.
- Types R and S have the same colors; the color does not tell them apart.
Old cables or cables to national codes (DIN, BS, JIS and others) use different colors. In older installations, do not identify the type by color alone.
How to confirm the type in the field
- Check the transmitter configuration and the sensor data sheet.
- Use a magnet: in type K the negative conductor is slightly magnetic; in type J the positive (iron) is magnetic.
- Measure the voltage with the sensor at a known temperature and compare it with the table for the type.
Extension and compensating cable
Extension cable has the same alloys as the thermocouple. Compensating cable uses different alloys that match the thermocouple only over a limited temperature range. Both need the right type and the right polarity; reversed, the cable causes a reading error.