On Accreditation and Calibration

Over the past few years a number of new quality requirements have been released that have created some confusion in the dimensional metrology community. I have been asked many of the following questions, and I hope that these answers are useful to you and your organization. -JGS

What is accreditation?
Accreditation is the process of proving competency of calibration and testing services. In addition to management and quality systems requirements, accreditation demands proof of the technical ability of the calibration provider. The measurement capability of the calibration service is quantified using measurement uncertainty, which is a key requirement in accreditation. Accreditation also verifies that calibration procedures are appropriate and valid. Accreditation is therefore critical to ensuring traceability of measurements.

What is measurement uncertainty?
Measurement uncertainty is an estimation of potential errors in a particular measurement process. Uncertainty is not resolution, not accuracy, not precision, and not gage repeatability and reproducibility, but uncertainty includes all that. When done properly, uncertainty evaluates all variables that influence the variation of measurement results, such as instrument errors and calibration, personnel, environment, and the measured workpiece. Uncertainty can be easy to estimate if the measurement process is well understood.

What are ISO/IEC Guide 25 and ISO/IEC 17025?
ISO/IEC Guide 25 has recently been replaced with ISO/IEC 17025:1999. These documents are international standards that lay out the requirements for calibration services providers worldwide. The requirements apply to all calibrations, everything from gage blocks (how to use gauge blocks) to CMMs, from pressure to mass, from force to frequency, etc. ISO 17025 has been adopted (with no changes) as an official American national standard, ANSI/ISO/IEC 17025:2000.

Who does accreditation?
Accreditation is performed by companies, public or private, called Accreditation Bodies (AB). Different countries have different rules; in the U.S., pretty much anybody could call themselves an AB; however, accreditation is only worth as much as the reputation and acceptance of the AB. National and international organizations exist to verify and recognize AB’s. Only two American AB’s have achieved national and international acceptance and recognition for accreditation in dimensional calibration: A2LA and NVLAP. A number of other AB’s have recently started up in the U.S. (e.g. LAB, NQA, PJL, and ACLASS) and some have been accepted by automotive companies. Most of these new AB’s are currently working towards national and international acceptance, but to date none of them have received that yet.

What are the accreditation requirements of QS-9000?
The Third Edition of QS-9000 includes sections 4.10.7 and 4.11.2.b.1 that require commercial and independent laboratories to be Guide 25 (17025) accredited, or equivalent. The intent of this requirement is that all calibrations done by commercial calibration providers, whether in a laboratory or in the field, whether from a third party or from an instrument manufacturer, must be accredited. The deadline to meet this requirement was January 1, 2001.

Are the calibration services of Mitutoyo America accredited to ISO/IEC Guide 25 (17025)?
Mitutoyo America is accredited to ISO/IEC Guide 25 (or 17025) by A2LA for the calibration of almost all Mitutoyo products, including laboratory calibrations (such as gage blocks and micrometers) and field calibrations (such as CMMs). The Mitutoyo calibration labs in Chicago and Detroit as well as the field service department have been accredited. Our A2LA accreditation satisfies the commercial calibration requirements in QS-9000. Besides Guide 25 and 17025, A2LA accreditations also cover the requirements of ANSI/NCSL Z540-1-1994, which is another standard for laboratory requirements. Since A2LA accreditations are recognized worldwide, Mitutoyo America calibrations are accepted in most other countries.

Is Mitutoyo America registered to either ISO 9000 or QS-9000?
Suppliers of manufactured goods must be registered to ISO or QS-9000. Suppliers of calibration services must be accredited to ISO 17025. Registration of calibration services to ISO or QS-9000 is inappropriate and usually prohibited; therefore, the calibration services of Mitutoyo America are accredited. However, accreditation contains all of the pertinent quality system requirements that are found in ISO or QS-9000, but accreditation goes further by checking the technical competence of an organization. Mitutoyo’s manufacturing plants are ISO or QS-9000 registered.

Does Mitutoyo America supply NIST Test Report Numbers?
NIST Test Report Numbers are not required, nor are they adequate, for satisfying traceability requirements. No quality systems standards, such as ISO and QS-9000, require the use of NIST numbers. Mitutoyo America recognizes the long history many have with using NIST numbers, and we do supply NIST numbers in some situations. However, verified uncertainty estimates and 17025 accreditation are the proper methods of demonstrating traceability.

Does Mitutoyo America include calibration due dates on certificates and labels?
In accordance to ISO 17025, calibration certificates and labels are not to recommend calibration due dates. ISO and QS-9000 require those using the measuring equipment, not the calibration services provider, to determine calibration intervals. Guidance on selecting calibration intervals can be found in many documents, such as ISO 10012-1:1992.

Does Mitutoyo America offer training in calibration and accreditation?
Mitutoyo America offers training courses in the use and calibration of our products. We also offer training in metrology, measurement uncertainty, and ISO 17025 accreditation.

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