TAF16

Thermocouples feature a simple structure and robust construction. Thermocouple sensors measure temperature based on the Seebeck effect. Two dissimilar conductors are connected to form a closed loop. A tiny voltage difference is generated in the loop whenever the temperatures at the two junctions differ. This voltage difference is known as thermovoltage or thermoelectromotive force. Its magnitude depends on the materials of the two conductors as well as the temperature difference between the “measuring junction” (where the two conductors are joined) and the “cold junction” (open ends of the conductors). For this reason, thermocouples are inherently used for temperature‑difference measurement. The absolute temperature at the measuring junction can be obtained if the cold‑junction temperature is known or measured separately for compensation. Standards IEC 60584 and ASTM E230/ANSI MC96.1 list common thermocouple conductor material combinations and their corresponding thermovoltage‑temperature characteristics.

High‑end Application

High‑temperature measuring conditions require high‑temperature thermometers with ceramic or metal thermowells, as well as thermocouples made of special materials such as platinum and rhodium. Thermowells of special materials effectively protect thermometers against mechanical and chemical damage in process operations and extend the service life of sensors. As a result, maintenance costs at measuring points can be reduced, product quality improved, and plant safety enhanced.