Thermocouple Sensors

A thermocouple consists of two dissimilar metals, joined together at one end. When the junction of the two metals is cooled or heated a voltage is produced that can be correlated back to the temperature. Most thermocouple alloys are commonly available as wire.
Thermocouples are manufactured in different combinations of metals andor calibrations. The calibrations most regularly specified by NSPI customers are J, K, T and E. High temperature calibrations include R, S, C and GB. Each calibration has a different temperature range and environment, although the maximum temperature varies with the diameter of the wire used in the thermocouple.
While the thermocouple calibration defines the temperature range, the maximum range will also be a factor the diameter of the thermocouple wire. Therefore, a very thin thermocouple may not reach the full temperature range.
Since thermocouples measure wide temperature ranges and are relatively rugged, they are very often used demanding industrial automation and process control applications. In selecting a thermocouple, the following criteria are key considerations:
Temperature range
Chemical resistance of the thermocouple or sheath material
Abrasion and vibration resistance
Installation requirements (may need to be compatible with existing equipment;existing holes may determine probe diameter)