Real-time control of a measurement process

The conventional industrial practice to correct (recalibrate) measuring instruments according to a fixed schedule (calibration interval) may waste money when the schedule is too tight or may provide a false sense of control when the schedule is too relaxed. Also, this approach may not generate data on real-time measurement errors that are crucial to draw management's attention to measurement concerns. We propose that the measurement process be interrupted according to an economically sensible schedule to check (interim test) the real-time errors with well-characterized check standards. When the observed error with the check standard exceeds an economic control limit, the measuring instrument should be corrected; otherwise correction is not needed. The proposed approach to limit the uncertainty of a measurement process is simple, sensible and generic. More important, it saves money by limiting the loss due to measurement error and the cost of control.