A Pt100 has nominal electrical resistance at .[ref]
Mercury Thermometer Alternatives: Platinum Resistance Thermometers (PRTs) by National Institute of Standards and Technology. Platinum Resistance Thermometers, opening explanation: conventional 100-ohm element at 0 °C
Here is the reference for the nominal element designation; it is distinct from the water triple point used in SPRT calibration. The following Pt100 local linear model deliberately stipulates one approximate response for calculations. New to topics? Read the docs here!