Measurement Uncertainty Cannot Always Be Calculated

The goal of this chapter is to stimulate reflections concerning calculation of measurement uncertainty. One basic question is here addressed: Is it always possible to calculate measurement uncertainty? In order to answer this question the conditions that should be met in order to calculate measurement uncertainty are briefly reviewed. Further, it is here provided an example related to a worldwide known and applied electromagnetic compatibility test method for which measurement uncertainty could not be calculated until a recent maintenance of the relevant standard. Calculation of measurement uncertainty for the new test method is here carried out in order to highlight the effectiveness of the improvement of the relevant standard.