7.6 Validity Of Previous Measuring Results


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Anyone have an effective method to validate the previous measuring results when the equipment is found not to conform to requirements ?

M Greenaway

Hope this isnt too simplistic, but check the last batch of product with a known good piece of equipment - keep going back until you find the last good batch.

Jerry Eldred

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We do a material review board. I'll have to go step-by-step to explain:

1. Unit is found out of tolerance by cal lab.
2. Tolerance limits and before/after adjustment readings are recorded by cal lab.
3. Those readings are presented to material review board.
4. Material review board consists of engineers involved in area where the test equipment was used.
5. Those engineers review the out of tolerance readings and compare them with how the unit may have impacted product.

The function of reviewing out of tolerance readings and how they impact product is the job of people who use the equipment. Calibration labs job is to provide them with good information and not make decisions on product. So we have never been any further involved than to provide the out of tolerance data to the user. Only those people who are skilled in the production application of the test equipment are qualified to make product decisions.

If you must make a decision, you would either need the measured readings from the previous calibration on the unit, or you would have to make some assumptions. With measured readings from the previous calibration, you could use linear interpolation and derive an estimate of approximately when the unit went out of tolerance. From there, make decisions on what errors were introduced on product measurements. If you do not have previous calibration data, you would need to pull product samples as in the above reply, and back track until you found satisfactory readings. From that, determine the amount of error in product measurements, and make a decision about product recall.
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