Thermocouple & RTD Wire Comes in Various styles and configurations. There are many factors to consider. If you need help just call 1-800-TIP-TEMP.
Thermocouple grade wire is used to manufacture thermocouple probes. Thermocouple grade wire is normally used for the junction and inside the stem sheath. This is because the thermocouple grade wire has a higher accuracy specification than extension grade wire.
Extension grade wire is a less expensive, lower grade wire. It is used to extend from the thermocouple probe to the control system or digital display. Extension grade wire is more economical due to the length requirements. Also, it is not in the process itself and does not play as critical a role nor does it experience the temperature extremes & temperature cycling.
Thermocouple Wire, RED is always negative. The other color-coded wire is always positive.