The nearly linear resistance versus temperature relationship for the PTS AT sensor is accurately modeled using the set of equations outlined here (temperature range dependent) with the known values (R₀, T, A, B, C). R₀ represents the nominal resistance at 0°C, T represents temperature in °C and A, B, and C represent the Callendar-Van Dusen constants that are derived from actual resistance measurements in accordance with IEC 60751. Figure A shows a graph of the R vs. T relationship (R_T/R₀ ratio versus temperature). A more detailed table outlining the R vs. T relationship can be found in the PTS AT datasheet.