How are RTD measurements linearized?

RTDs have nonlinear resistance-temperature characteristics described by Callendar-Van Dusen equation: R(T) = R0(1 + AT + BT^2 + C(T-100)T^3). Linearization methods include: lookup tables (store resistance-temperature pairs, interpolate), polynomial approximation (fit polynomial to calibration data), analog linearization circuits (less common now), and standard equation calculation. Pt100 (100 ohm at 0C) is most common. Modern transmitters and PLCs have built-in linearization for standard RTD types. Three-wire and four-wire connections eliminate lead resistance errors.