Matrix Presentation of Uncertainties Propagation in the Realization of ITS-90 Temperature Scale using Standard Platinum Resistance Thermometers

The paper presents a matrix approach to the propagation of uncertainties in the realization of the ITS-90 using Standard Platinum Resistance Thermometers (SPRT) calibrated at Defining Fixed Points (DFPs). The procedure allows correlations to be included between SPRT resistances measured during the calibration at the DFPs (i.e., the realization of the ITS-90) and the resistances measured during the subsequent use of the SPRT to measure temperature T₉₀. The example also shows the possible contribution of these correlations to the overall temperature uncertainty measured by a calibrated SPRT.