The resistancetemperature (RT) relationship plays a central role in resistance temperature detectors (RTDs). The RT relationship of some common RTD materials are illustratrated in the following schematic where the yaxis is the normalized resistance with respect to resistance at 0 °C (32 °F), xaxis is the temperature.
ResistanceTemperature Relationship for some RTD materials
For a given material, the resistance at any temperature can be obtained by curvefitting the RT curve. Suppose that a nth degree polynomial leastsquare curvefit is used. The temperature function will then be,
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.
