Widerstandstemperaturfühler

Widerstandstemperaturkoeffizient (temperature coefficient of resistance, TCR) describes how the electrical resistance of a material changes with temperature. It is usually represented by the coefficient α, defined by R(T) = R0 [1 + α (T − T0)], where R0 is the resistance at a reference temperature T0. The coefficient is typically specified at a reference temperature—often 0°C, 20°C, or 25°C—and is measured in per-degree Celsius or in parts per million per degree Celsius (ppm/°C).

For most metal conductors, α is positive, meaning resistance increases with temperature. In many semiconductors and thermistors, α can be negative over part of the temperature range, so resistance falls as temperature rises. The magnitude and sign of α depend on material, temperature, and microstructure, and may vary significantly outside the reference range.

Common devices that exploit the TCR include resistance temperature detectors (RTDs), thermistors, and certain sensors used for linearization and compensation in electronic systems. RTDs, such as platinum-based sensors, typically have small, stable positive α values around 0.00385/°C, enabling precise temperature measurement. Thermistors include NTC types with large negative α and PTC types with positive α, used for temperature sensing and protection, respectively.

Applications rely on accurate TCR specification and careful calibration. Designers use TCR to compensate for temperature-induced resistance drift, to predict sensor behavior across operating temperatures, and to correct for self-heating in circuits. TCR is specified in datasheets under defined reference conditions and can vary with temperature range, annealing, and device geometry.

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