posted 23 February 2000 12:36 PM               

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From [email protected] Wed Feb 23 05:04:00 2000
Date: 23 Feb 2000 06:53:09 -0500
From: "Ito, Yochio"
To: cheech
Subject: Criteria for calibration certificates

I was charged in the pre-auditory for the criteria used for the validation of the calibration certificates. Could you please help me? How can I define such a criteria? Based in what kind of information should I choose it? My instruments are basicaly torque wrenchers.

Thanks in advance

posted 23 February 2000 12:52 PM               

"The recorded information shall include"

a) the description and unique identification of the equipment;
b) the date of which each confirmation was completed;
c) the calibration results obtained after and where relevant before any adjustment and repair;
[GUIDANCE In some instances, the calibration result is given as a compliance with or failure to comply with a requirement]

d) the assigned confirmation interval
e) identification of the confirmation procedure
f) the designated limits of permissible error
g) the source of the calibration used to obtain traceability
h) the relevant environmental conditions and a statement about any corrections thus necessary;
i) a statement of the uncertainties involved in calibrating the eqiupment and of their cumulative effect;
j) details of any maintenance such as servicing, adjustment, repairs or modifications carried out;
k) any limitations ot use;
l) identification of the person(s) performing the confirmation;
m) identification of the person(s) responsible for ensuring the correctness of the recorded information;
n) unique identification (such as serial numbers) of any calibration certificates and other relevant documents concerned.

The supplier shall maintain clear documented procedures on the retention (including the duration) and safeguarding of records. Records shall be kept until it is no longre probable that they may need to be referred to."

That is the quote from ISO 10012. That is a lot. A number of those requirements are somewhat vague, and can be interpreted in a variety of ways. For example the statement of uncertainties may be something as simple as a statement that all measurement uncertainties of the measurement standards did not exceed 25% of the tolerance for each calibrated parameter, or where that is not achievable, an alternate statement that state-of-the-art limits prevented it and methods were utilized to minimize the effect of those uncertainties on calibration results. Item (g) refers to the measurement standards used. The specific measurement standards used must be listed. I personally don't consider a certificate of calibration missing listing of measurement standards used as acceptable.

Hope this was of help.