The purpose for measurements and understanding their uncertainties (The Basic, ISO and ASME uncertainty models compared)

This paper proposes an approach to uncertainty analysis that would meet the needs of all users and be in accordance with both the ASME Standard and ISO Guide. As the technologies for the estimation of measurement and test uncertainty developed, several models took hold. One was developed in the US by the ASME PTC19.1 Committee and the other largely by metrologists and the ISO. These two models have more similarities than differences. This paper discusses the primary advantages and disadvantages of those two models as well as that of a third simple, Basic model. This paper concludes with an approach to uncertainty analysis that meets the needs of all three models plus several detailed example uncertainty calculations.