ITS-90 non-uniqueness from PRT subrange inconsistencies over the range 24.56 K to 273.16 K

摘要

We have performed calculations to study ITS-90 non-uniqueness from subrange inconsistencies over the range 24.5561 K to 273.16 K, where the scale is defined by an interpolating platinum resistance thermometer (PRT) that is calibrated via sets of defined fixed points. For this work, subrange inconsistency calculations have been performed on eighteen PRTs; fourteen are standard PRTs and four are miniature PRTs. The inconsistency uncertainties, which result from propagation of fixed-point uncertainties, have also been calculated. The calculations show that PRT subrange inconsistencies in the temperature region studied can be as large as 1 mK. We have also studied possible correlations between PRT subrange inconsistencies and other PRT properties/parameters that are simpler to determine; these studies show that there is a correlation between the average magnitude of the inconsistencies and the value of a certain calibration coefficient. Finally, for the range studied we have used a statistical analysis on the inconsistencies of the PRT ensemble to calculate a standard uncertainty to the ITS-90 temperature T_(90) due to the inconsistencies. Over the temperature intervals 25 K <= T_(90) <= 50 K and 100 K <= T_(90) <= 200 K, this uncertainty dominates those propagated from fixed-point uncertainties.