Thermocouple Reference
Thermocouple Wire Color Codes
Color codes have been adopted by various national and international standard agencies for identification of thermocouple wire and thermocouple products. In the United States, thermocouple-grade wire normally has a brown overall jacket. For Types B, R and S, the color codes relate to the compensating cable normally used.
| Type | United States ANSI 96.1 | United Kingdom BS 1843 | West Germany DIN 43714 | France NF C42-323 | Japan JIS C1610-1981 |
|---|---|---|---|---|---|
| E | Purple + Purple – Red |
Brown + Brown – Blue |
Black + Red – Black |
- | Purple + Red – White |
| J | Black + White – Red |
Black + Yellow – Blue |
Blue + Red – Blue |
Black + Yellow – Black |
Yellow + Red – White |
| K | Yellow + Yellow – Red |
Red + Brown – Blue |
Green + Red – Green |
Yellow + Yellow – Purple |
Blue + Red – White |
| N | Orange + Orange – Red |
- | - | - | - |
| B | Grey + Grey – Red |
- | Grey + Grey – Red |
- | Grey + Red – White |
| R | Green + Black – Red |
Green + White – Blue |
- | - | Black + Red – White |
| S | Green + Black – Red |
Green + White – Blue |
White + Red – White |
Green + Yellow – Green |
Black + Red – White |
| T | Blue + Blue – Red |
Blue + White – Blue |
Brown + Red – Brown |
Blue + Yellow – Blue |
Brown + Red – White |
Thermocouple Wire Color Codes
| Type | J | K | T |
|---|---|---|---|
| Material | Iron (+) vs. Constantan (-) |
Nickel (10%) Chromium (+) vs. Nickel (5%) Aluminum Silicon (-) |
Copper (+) vs. Constantan (-) |
| Temperature Range | 0°C to 760°C | 0°C to 1370°C | -160°C to 400°C |
Comparison of Temperature Transducers
| Type | Thermocouple | RTD | Thermistor |
|---|---|---|---|
| Advantages | • Self-powered • Simple, rugged • Lower cost • Wide temperature range |
• Most stable • Most accurate • Better linearity |
• High output • Fast |
| Disadvantages | • Nonlinear • Low voltage • Least stable • Least sensitive • Reference required |
• Expensive • Current source required • Small resistance change • Low absolute resistance • Self-heating |
• Nonlinear • Limited temperature range • Fragile • Current source required • Self-heating |
Time Contraints
The time constant of any sensor is defined as the time required for that sensor to respond to 63.2% of its total output signal when subjected to a step change. The step change can be either an increase or decrease in the parameter being measured. Five constants are required for a sensor to reach 99% of its total change. The graph to the right illustrates this relationship.