Compatibility in industrial measurements

In assessing the quality of an industrial product it is often necessary to state the compatibility between few (for instance two) independent measurement results. The case of two instruments with independent metrological characteristics but having received appropriate calibration and uncertainty statements is here considered. They will always produce compatible results when applied to the same measurand of negligible intrinsic uncertainty. Different hypotheses may however be assumed in determining this measurand by means of a central value and a width for its uncertainty interval. Furthermore, in the case of industrial measurements, measurands have a non negligible intrinsic uncertainty, that is usually increased by the object and test conditioning. It may therefore be necessary to consider the full range of the probability distribution for the difference between the outputs of the two instruments. The statement of compatibility conditions becomes therefore more difficult. It is a task of the standardising organisations to prepare internationally valid procedures for attaining univocal conclusions.