Comparison of Resistance Versus Thermodynamic Temperature of Platinum Resistance Thermometers with the ITS-90

Data relating the resistance of high temperature platinum resistance thermometers with thermodynamic temperatures, which were independent from those used to derive ITS-90, have been compared with ITS-90. Within the accuracy of the photoelectric pyrometry involved, ±0,40°C at the freezing point of silver, the measured thermodynamic temperatures agreed with the temperatures obtained using the ITS-90. In measurements performed during a 1,5 year period the typical random uncertainties, evidenced by variations in the resistance of platinum resistance thermometers at the triple point of water, were equivalent to ±0,015°C at the freezing point of silver, whilst, in this period, the drifts in the measured values of the resistance ratio at the freezing point of silver were equivalent to 0,03°C.