Eign-Limits Uncertainty Methodology for Temperature Calibration by Fixed Points and Comparison

Calibration measurement uncertainty of Platinum Resistance Thermometer (PRT) was estimated in International Temperature Scale 1990 (ITS-90) at defined fixed points [1]but it was not gives a criteria to find the uncertainty at un-calibrated point within sub ranges between fixed points experimentally, the uncertainty was estimated mathematically. This paper explains the estimation of measuring uncertainty for PRT based on mathematical module able to detect the uncertainty at specified un-calibrated temperature (Intra limits propagation) and the expectation for the Eign-limits using modified supplementary ITS-90equation, this equation was used by modification the factor of sensitivity
according to each uncertainty source. It was covered the range from 0°C to 420°C. (Water Triple Point (WTP) 0.01 oC, Gallium Melting Point (GMP) 29.76 °C, Tin Freezing Point (SnFP) 231.9 °C and Zinc Freezing Point (ZnFP) 419.5 °C). Same range was covered in the calibration by comparison method. From this study, a validation for the equation has carried out, the uncertainties in the sub ranges were found to be less than 0.2 mK difference between the real measurements and statistically expectation.