Before making a measurement, the quantity must be clearly defined, bearing in mind the purpose for which the experimental result is required. The quantity referred to is the measurand. In addition, for measurement results to be fit for purpose, a validated measurement procedure needs to be available and must be applied using a calibrated measuring system. In this context ‘fit for purpose’ means that, when the measurement procedure is applied, the quantity intended to be measured is measured, and the uncertainty in the measurement results is acceptable. The concept of target measurement uncertainty. is used to describe the maximum measurement uncertainty that can be accepted by the customer for a specific application.
Preliminary to making a measurement: Terminology in Analytica Measurement Introduction to VIM 3
