When purchasing a calibration, three terms soon come up: ISO 9001, ISO/IEC 17025 and traceability. They are regularly used interchangeably, even though they mean very different things. The result: companies pay for a certificate they do not need, or discover during an audit that their certificate does not match what a customer requires.
In this article you will read what each term means, how they relate to each other and which certificate you need in which situation. We are open about our own position in this. How we work in our calibration laboratory is described on a separate page.
ISO 9001: an organisation's quality system
ISO 9001 is a standard for quality management systems. An organisation with an ISO 9001 certificate has had an assessment confirming that its processes are described, controlled and improved. That can be a manufacturer, a service provider or a calibration laboratory.
For measuring equipment, ISO 9001 requires among other things that it is suitable for its purpose, that it is calibrated or verified at specified intervals against standards traceable to international or national standards, and that you assess whether previous measurement results have been affected when an instrument is found to deviate. You will find these requirements in clause 7.1.5 of the standard.
It is important to realise that an ISO 9001 certificate says something about an organisation's management system. It is not a formal assessment of the technical competence to perform a specific measurement. That is what ISO/IEC 17025 is for.
ISO/IEC 17025: accreditation of laboratories
ISO/IEC 17025 contains requirements for the competence of testing and calibration laboratories. A laboratory can be accredited against it by a national accreditation body: the Dutch Accreditation Council (RvA) in the Netherlands, BELAC in Belgium and DAkkS in Germany.
Accreditation assesses not only the quality system but also the technical side: methods, uncertainty calculations, references, environmental conditions and the expertise of staff. An accreditation applies to a defined scope, with specific quantities, measuring ranges and measurement uncertainties. Only calibrations within that scope are covered by the accreditation. With an accredited certificate, therefore, also check whether your measurement falls within that scope.
Traceability: the unbroken chain
Traceability means that a measurement result can be related, through an unbroken chain of calibrations, to a national or international standard. Each link in that chain has a known measurement uncertainty.
For mass, that chain looks roughly like this:
- the national mass standard, maintained by the national metrology institute;
- reference weights of a calibration laboratory, calibrated against a higher level in the chain;
- working or check weights, calibrated against those references;
- your scale, calibrated with those weights.
A certificate should state which references were used, so that the chain can be followed. Traceability is therefore not a separate type of certificate. It is a property that both an accredited and a non-accredited certificate must have. The difference lies in the way the laboratory's competence has been demonstrated. What else a certificate contains is explained in calibration certificate explained.
Checking traceability in practice
During an audit you want to be able to show the chain without being a metrologist yourself. Pay attention to these points:
- the certificate names the reference weights or reference instruments used, with their identification;
- those references have themselves been calibrated, and the laboratory can demonstrate this on request;
- the measurement results are accompanied by a measurement uncertainty, because without uncertainty there is no complete link in the chain;
- the measurement uncertainty suits your application: a certificate can be traceable and still be too coarse for your requirements.
For weights according to OIML R111 there is an additional guide. The expanded uncertainty of the calibration may be no more than one third of the maximum permissible error (mpe) of the class. If the uncertainty is larger, the weight cannot be assigned to that class on the basis of that calibration.
Which certificate do you need?
The choice depends on what your own standard, your customer or your sector requires. An overview of situations we often encounter:
| Situation | Usually appropriate | Notes |
|---|---|---|
| Manufacturing company with ISO 9001 | Traceable calibration certificate | The standard requires traceable calibration at specified intervals, not accreditation. |
| Food company with HACCP, BRC or IFS | Traceable calibration certificate | Check whether your customer imposes additional requirements. |
| GMP environment | Traceable certificate, unless your procedures or customer require accreditation | Record the choice and its justification in your quality documentation. |
| Your own laboratory is ISO/IEC 17025 accredited | Accredited certificate | The traceability of your own accredited measurements must be demonstrable at that level. |
| Customer or sector explicitly requires accreditation | Accredited certificate | Ask which measuring instruments this applies to; often it is not all of them. |
| Scale used for selling by weight | Valid legal verification, possibly supplemented with a calibration certificate | A calibration certificate does not replace legal verification; see the Dutch Metrology Act and scales. |
If in doubt, ask your auditor or customer exactly which requirement is stated in the standard or the contract. We regularly see an accredited certificate being requested when the underlying requirement is traceability. What else an auditor checks is set out in the measuring equipment management checklist.
Common misunderstandings
- An ISO 9001-certified laboratory is accredited. No. Certification and accreditation are different things, assessed by different parties against different standards.
- An accredited certificate is always better. It provides additional assurance about the laboratory's competence, but the measurement uncertainty is not automatically smaller and it is not necessary for every application.
- Without accreditation a calibration is not traceable. A non-accredited laboratory can also calibrate traceably, provided the chain and the measurement uncertainty are documented.
- A calibration certificate makes a scale legally verified. No. Legal verification is a statutory inspection under the Dutch Metrology Act and is separate from calibration.
How MASSLAB helps you
Calibrations are performed according to internally established procedures based on the relevant requirements of ISO/IEC 17025. Where applicable, measurement results are stated with measurement uncertainty and supported by traceable measurement references. Our calibrations of weights and scales are traceable to national standards, and our certificates state the references used and the measurement uncertainty. For most quality systems, that is what is required. If you do need an accredited certificate, we can arrange this on request through an accredited partner. Read more about our working method at our laboratory. Your certificates are available in the customer portal.