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W138 — Implementing ISO 17025 Measurement Uncertainty Requirements in Software

ISO/DIS 17025, “General Requirements for the Competence of Testing and Calibration Laboratories,” states that “calibration certificates shall contain the measurement results including the measurement uncertainty.” What does that mean? Is it simply a Test Uncertainty Ratio (TUR) calculation, or are there other factors involved? Using the “Guide to the Expression of Uncertainty in Measurement,” it certainly is more than a TUR calculation. This application note describes the implementation of the measurement uncertainty calculation in Fluke’s T/CAL® automated calibration software package. Compliance with ISO/DIS 17025 is discussed.