Precision and Calibration Procedures?

First you need to define the requirements of the audit. An in-house audit based on an in-house standard is a lot different than an ISO audit done by a third party agency but both still need to be defined in order to be effective.

There are a few things about old records but the leading rule is if you are not required to keep them get rid of them. Auditors rarely care that a record is twenty years old, they only see that it doesn't meet current standards and you are in possesion of it.

How should the precision and calibration of a piece of equipment be expressed as per "Calibration procedures shall include specific directions and limits for accuracy and precision."?

If I understand you correctly you need to stipulate the specifications standards for your equipment. Depending on your auditors requirements you can either reference the manufactures manual or copy the sections you need into your own in-house documentation.

The trick is to define your own rules.

E.g. 'This jig/instrument is for indication purposes only'

Work to shop copies if it is appropriate.

The point is to have control, not unnecessary precision.

Always quote as lose a spe'c or tolerance as is reasonably possible.

Check these things back to as few fully calibrated instruments as possible, as long as you have traceability.

Say, have one 'scope and one Digital multimeter calibrated yearly...the others can be 'for indication only' When in doubt check back to the calibrated ones.

Build your own test equipment and check it yearly or monthly against the calibrated pieces of equipment.

I once met an auditor who wanted every steel rule calibrated....This maybe ok in some cases, and admittedly I've seen two plastic rule which disagreed by 3mm!

The key thing to bear in mind is fitness for purpose.

Bottom line. write the system for yourself. The system is for you not the other way round.

Hope this helps.

To start with............

Keep in mind that calibrations have no value unless they are traceable to an accepted reference standard and that standard is also traceable to a master.

All calibrations records Must use approved precedures to be valid and have references listed, with logs of calibrating times, and results.

I would think your best bet would be to get guidance from the organization or inspector that did the audit.

As long as they don't expect you to pay extra for it!

...advice should come with the audit.

Remember you are paying them to do work for you, be sure you get your money's worth.

I found this statement in ANSI/NCSL Z540-1 (1994), "Calibration procedures shall contain the required range and tolerance or uncertainty of each item or unit parameter being calibrated or verified.

In addition, the procedures shall contain the generic description of the measurement standards and equipment needed with the required parameter, range, tolerances or uncertainties, and specifications for performing the measurement of the calibration or verification, and/or representative types(manufacturer, model, option) that are capable of meeting the generic description for the measurement standards.

The procedures shall be consistant with the accuracy required and with any standard specifications relevant to the calibrations/verifications concerned".....

OK...let's break down this bureaucratic gobblygook to some rational statements. Here's what they want; "calibration procedures shall contain the required range and tolerance (or uncertainty) of each item or unit parameter being calibrated or verified".

This simply asks you to identify what can and what can't be calibrated using the method outline in you procedure.

I won't repeat the next incredibly long sentence in the above quotation but it boils down to this; your procedures must list and "generically " describe (i.e. oscilloscope, 5 digit DMM, etc.) all the equipment, standards, environment and anything else required to perform the calibration.

The last statement simply requires your procedures to meet the accuracy requirements of the items being calibrated.

Hope this helps. You might check out ISO/IEC 17025 (1999) also.