Thermocouple Extension Wire Color Codes & Specifications
| ANSI Code | ANSI Color Code | Positive (+) Lead | Negative (-) Lead | Temperature Range | Initial Calibration Tolerances | |
|---|---|---|---|---|---|---|
| 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.
† 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.
| Type Wire | Measuring Junction Temperature |
|---|---|
| SX | Greater than 1598°F (870°C) |
| BX | Greater than 1832°F (1000°C) |
