Thermocouples are the only known self-powered temperature sensors. In its most simple form a thermocouple is formed by the junction of two dissimilar metals.
Simulation of output voltage from heating a thermocouple
When the junction is heated a voltage is generated between the two conductors. This voltage varies with temperature and is unique for a given pair of conductor materials and is specified in international standards (International Electrotechnical Commission, publication 584-1, IEC 1977).
Thermocouples manufactured to the international standards are fully interchangeable and their performance is independent of the manufacturer or the country of origin.
Standard Thermocouple Types
| Type |
Commonly Used Names |
Temperature Range (ºC) |
| J |
Iron – Copper Nickel |
-200 to 750 |
| K |
Nickel Chromium-Nickel Aluminium |
-180 to 1100 |
| T |
Copper-Copper Nickel |
-250 to 370 |
| N |
Nicrosil – Nisil |
-180 to 1100 |
| S |
Platinum 10% Rhodium – Platinum |
0 to 1500 |
| R |
Platinum 13% Rhodium – Platinum |
0 to 1500 |
| B |
Platinum 30% Rhodium – Platinum 6% Rhodium |
0 to 1700 |
| E |
Nickel Chromium – Copper Nickel |
0 to 850 |
|
