Fig. 52: “Don’t tell me you specified the wrong size to Hong Kong again. (Cartoon by Manfred Pühn).

Measuring Accuracy

Colloquially speaking, the term “measuring accuracy” refers to everything that characterizes the precision of measured results. However, a closer look shows that a distinction must be made between various categories:

• definition of the characteristics of a coordinate measuring machine in order to specify its measuring performance and define processes for checking this,
• processes for determining the uncertainty of measured results when measuring part features taking all influencing factors into account,
• defining and checking a suitable value for the relationship between measuring uncertainty and feature tolerance.

The traceability of the measured results to international standards is an indispensable aspect of all of these observations. It ensures that measurements can be performed in the same manner throughout the world (Fig. 52). In cases where processes are to be controlled only internally, observation of the repeatability alone often proves sufficient. The aspects specified above will be covered in more detail in the following sections.