RTD - Abbreviation for Resistance Temperature Detector.
Resistance temperature detectors operate on the principle of changes in electrical resistance of pure metals and are characterized by an almost linear positive change in resistance with temperature.
Typical elements used for RTDs include nickel (Ni) and copper (Cu), but platinum (Pt) is by far the most common because of its wide temperature range, accuracy, and stability.
RTDs are more accurate and more linear than thermocouples and generally much more costly and slower responding. The platinum RTD temperature sensing element is the most accurate and stable sensor over time and temperature.
RTD element technologies are constantly improving, further enhancing the quality of the temperature measurement. Typically, a data acquisition system conditions the analog signal from the RTD sensor, making the analog translation of the temperature usable in the digital domain.
Figure 1.Industrial RTDs