Expression of the uncertainty of measurement in the calibration of thermometers - Part I: Standard platinum resistance thermometers

A model is proposed for the calibration of a standard platinum resistance thermometer (SPRT) in accordance with the BIPM recommended procedures to realize the International Temperature Scale of 1990 (ITS-90). The model is used to obtain the standard uncertainty of measurement associated with the temperature indicated by the thermometer. The difference between calibration uncertainty and user's uncertainty is established. Equations are illustrated by an example that considers the ITS-90 subrange from 273.15 K to 692.677 K. The approach closely follows the rules in the ISO Guide to the Expression of Uncertainty in Measurement.