Resistance-Temperature Relationship |

The resistance-temperature (R-T) relationship plays a central role in resistance temperature detectors (RTDs). The R-T relationship of some common RTD materials are illustratrated in the following schematic where the Resistance-Temperature Relationshipfor some RTD materials For a given material, the resistance at any temperature can be obtained by curve-fitting the R-T curve. Suppose that a Some references suggest to express the resistance as a function of temperature (rather than temperature as a function of resistance), i.e., Although such a relationship is mathematically correct, its usefulness is limited. After all, we are interested in determining temperature from a resistance measurement. |

A Simplified Case |

Some materials have an almost linear R-T relationship within a certain temperature range, T < T. Such a linear function would take the form,
_{2}Rearranging to bring temperature out gives, where a is the average temperature coefficient of resistance in the ( T) temperature range, i.e., a is the slope of the R-T line.
_{2}Both the measured temperature and the reference temparature should be within the ( T) temperature range,
_{2}T < {_{1}T, T} < _{Ref}T_{2} |