TAF11

Thermocouples have a simple structure and rugged build. Thermocouple sensors measure temperature based on the Seebeck effect. Two dissimilar conductors are connected to form a closed loop. A tiny voltage difference arises in the loop whenever the temperatures at the two junctions are different. This voltage difference is called thermal voltage or thermoelectromotive force. Its magnitude depends on the materials of the two conductors, as well as the temperature difference between the "measuring junction" (the joint of the two conductors) and the "cold junction" (the open‑circuit ends of the conductors). Therefore, thermocouples are generally only used for temperature‑difference measurement. The absolute temperature at the measuring junction can be obtained if the cold‑junction temperature is known, or after separate temperature measurement and compensation. Standards IEC 60584 and ASTM E230/ANSI MC96.1 list common thermocouple conductor material combinations and their corresponding thermal‑voltage‑to‑temperature characteristics.

High‑end Application

Measuring points with extremely high process temperatures require thermometers equipped with ceramic sheaths and thermocouples made of special metals such as platinum and rhodium. Sheaths of special materials protect the working elements during measurement against mechanical damage and chemical corrosion, and extend the service life of the sensor. As a result, maintenance costs for measuring points are reduced, product quality is improved, and production safety is enhanced.