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Session Topic: 8C, Calibration Intervals

   

Paper Title: Calibration Intervals: A Practical Approach?

   

Date & Time: WEDNESDAY, August 7, 2002

 

2:30 - 4:00pm - PARALLEL SESSIONS - SESSION 8

   

Speaker: Gilbert Brigodiot EADS Launch Vehicles

Email: gilbert.brigodiot@launchers.eads.net

   

The problem of the determination of calibration intervals is as old as metrology. Despite continuous efforts on this subject (NCSL RP1 for example), the methods offered are typically general and theoretical. Metrologists are reluctant to use statistical models they don't control. What's more, standards and auditors require a document that sets the periodicity. The annual periodicity (with multiples and sub-multiples) seems to be normal, as for sowing and harvest. Calibration intervals are taken from external sources, copying the choices of military organizations. But a lot of money could be saved by optimization of calibration intervals ! For a long time, the author has been trying to find THE solution, based on statistics, reliability models, prediction theories, analysis of drifts and so on. The technical have not been commensurate with his expectations. There is no choice but to accept the fact that it's impossible to guess everything just from the results of a calibration. A new approach is being tested, favoring the experience of the metrology lab and the objective satisfaction of the needs of the measuring equipment user. The methodology focuses on the increase of the risk in the measurement process versus the increase of the drift of the equipment. A software has been developed to help for decision making, balancing the pro and the con for extension of a calibration interval. This approach presented is being tested on more than 1000 items of measuring equipment. The results are promising and seem to be acceptable to auditors in the ISO 9000 : 2000 context.

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