Evaluation of Out-of-Tolerance Risk in Measuring and Test Equipment

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Evaluation of Out-of-Tolerance Risk in Measuring and Test Equipment (140.25 KB)

In the interest of providing reliable and accurate measuring and test equipment to customers, a manufacturer or calibration service provider should understand and control out-of-tolerance risk—the probability an instrument is actually out of tolerance after passing calibration. While the equipment is expected to be in tolerance when it leaves the calibration laboratory, it is just as important that it remain in tolerance during use. A manufacturer also does not want to see too many products fail calibration or be found out of tolerance later at recalibration. Pass yields must be high. Risks and yields are dependent on product specifications, guard bands, calibration uncertainties, and product characteristics, such as long-term stability, ambient temperature sensitivity, and linearity. This paper provides formulae for calculating various relevant risks and yields. Examples are given. Calculations are verified by computer simulation.