L'analyse des systèmes de mesure (MSA) est un facteur essentiel dans le monde de la métrologie, car elle détermine la capacité d'un instrument à effectuer une tâche de mesure.
In production measurement technology, a measurement process analysis (MPA) or measurement system analysis (MSA) has to be carried out. MPAs or MSAs are useful to determine the accuracy of measurements in an experimental set-up and to assess measurement quality by making sure the measuring instrument is capable of completing the measurement task adequately and accurately.
There are different methods which can be used to determine the capability of the measuring equipment and the measuring process under real operating conditions – by means of repeated measurements based on standards or real samples, and with or without user influence. In general, these procedures are also known as Gage R&R (Repeatability & Reproducibility) methods. Different industry standards imply varying numbers of measurements, users, parts, repetitions and limits.
Cg and Cgk values define the measurement process capability, which is determined by analyzing the standard deviation/precision and the bias/trueness of a measurement system. Usually, a measurement system must have a measurement process capability Cg, Cgk > T, with T varying depending on the industry, company or component. The larger Cgk, the more capable the instrument – here is the mathematical formula behind it:
T ... tolérance dans le dessin
S ... écart-type de la mesure
xg- xm.... biais de la mesure par rapport à une valeur de référence
Dans la pratique, d'autres facteurs d'influence - par exemple les facteurs humains, l'appareil de mesure ou l'environnement - doivent être réduits. Voir ici le diagramme d'Ishikawa :