Perhaps no concepts have been more abused than those related to controlling measurements. For decades it was common in many industries to calibrate measuring and test equipment to ensure it met its own specifications for accuracy and precision. Complex and expensive systems were developed to do the calibrations as scheduled. There was little emphasis on controlling the relationship between the requirements being measured and the precision, accuracy, and stability of the overall measurement system. I’ve seen many situations where measuring devices had tolerances that were looser than the tolerances of the characteristic being measured, and caused the entire control loops to behave erratically--and the managers all wondered why.

By the time ISO 9001 was first issued in 1987, this had begun to change. Some industries had begun to emphasize what should be measured so that appropriate measurement equipment was selected. Still, even today it’s not uncommon to see the wrong equipment being used for a measurement. The most important focus in this area is to establish controls to ensure that measurement capability exists. In other words, the measurement system must be accurate and precise enough to ensure that measurements meet measurement requirements.

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