Accuracy, repeatability, performance—knowing how to interpret specifications for measuring devices and systems is important. This month I’ll talk about accuracy specifications for video measuring machines, which I described last month. The concepts apply to other measuring devices as well. The concepts apply to other measuring devices as well.

Let’s start with a definition of accuracy: The degree of conformity of a measured or calculated value to its actual or specified value.

The measured or calculated value for a video measuring machine is typically a length, distance, or size value. Accuracy, therefore, is how closely the video measuring machine measures an actual or specified length, distance, or size. The degree of conformity is the accuracy specification where the smaller the accuracy value, the closer the conformity to the actual or specified value. The best-case scenario is an accuracy specification of zero, or exactly equal to the actual value. If only that were possible!

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