Thermocouples are the most commonly used temperature sensors.
A thermocouple is created when two dissimilar metals touch and the contact point produces a small open-circuit voltage that corresponds to temperature. This thermoelectric voltage is known as Seebeck voltage and is nonlinear with respect to temperature. Thermocouples require signal conditioning.
Thermocouple types differ in composition and accurate range:
Thermocouple Type | Positive Conductor | Negative Conductor | Temperature Range (°C) |
---|---|---|---|
J | Iron | Constantan | –210 to 1200 |
K | Chromel | Alumel | –270 to 1372 |
N | Nicrosil | Nisil | –270 to 1300 |
R | Platinum-13% Rhodium | Platinum | –50 to 1768 |
S | Platinum-10% Rhodium | Platinum | –50 to 1768 |
T | Copper | Constantan | –270 to 400 |
B | Platinum | Rhodium | 0 to 1820 |
E | Chromel | Constantan | –270 to 1000 |