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

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... d 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 o C,