|
A thermocouple consists of two dissimilar metals, joined together at one end, which produce a small voltage when heated (or cooled). This voltage is measured and used to determine the temperature of the heated metals. The voltage for any one temperature is unique to the combination of metals used.
Thermocouples are available in different combinations of metals, usually refered to by a letter, e.g. J, K etc. Each combination has a different temperature range and is therefore more suited to certain applications than others. Although it is worth noting that the maximum temperature varies with the diameter of the wire used in the thermocouple.
Guidance for the selection and use of devices for measuring temperature is given in the relevant sections of British Standards Specification, BS 1041, Temperature Measurement.
| ASTM Type |
Conductor Combination |
Temperature Range | |
| °F | °C | ||
| B | Platinum 30% Rhodium / Platinum 6% Rhodium |
2500 to 3100 | 1370 to 1700 |
| E | Nickel-chromium / Constantan | 32 to 1600 | 0 to 870 |
| J | Iron / Constantan | 32 to 1400 | 0 to 760 |
| K | Nickel-chromium / Nickel-aluminum | 32 to 2300 | 0 to 1260 |
| N | Nicrosil / Nisil | 32 to 2300 | 0 to 1260 |
| R | Platinum 13% Rhodium / Platinum |
1600 to 2640 | 870 to 1450 |
| S | Platinum 10% Rhodium / Platinum |
1800 to 2640 | 980 to 1450 |
| T | Copper / Constantan | -75 to +700 | -59 to +370 |
|
