What does a calibration certificate contain?

A calibration certificate is the proof that your scale does what it should. But not every piece of paper with that word on it is the same, and an auditor knows the difference.

What it contains at a minimum

The identification of the instrument (make, type, serial number), the place and date of calibration, the check weights used with their class and traceability to the national standard, the ambient conditions, the measuring points across the range with the reading and the deviation at each point, the measurement uncertainty, and who carried out the measurement. A certificate without measurement uncertainty is not a calibration certificate but a check report.

Which measurements belong in it: EURAMET cg-18

The European calibration guide EURAMET cg-18 (Calibration Guide No. 18, not a legal directive like 2014/31/EU) describes how a non-automatic weighing instrument should be calibrated. Three tests: repeatability, weighing the same weight several times; eccentric loading, a weight in the centre and on the four corners of the platform; and error of indication, increasing and decreasing across the whole range. From those three follows the measurement uncertainty, and from that uncertainty follows whether the scale is suitable for the work you do with it. Our certificates follow that structure.

ISO certificate or accredited certificate

An ISO certificate (also called a factory certificate or workshop certificate) is issued by the supplier or the service company, using weights that have themselves been calibrated traceably. That is what ISO 9001, HACCP and GMP generally require. An accredited certificate comes from a laboratory accredited under ISO/IEC 17025 by a national body: UKAS in the UK, DAkkS in Germany, RvA in the Netherlands, BELAC in Belgium. Such a certificate is internationally recognised and is requested by laboratories that are themselves accredited, in pharmaceuticals and by some customers in automotive and aerospace. For KERN balances and KERN weights we supply the DAkkS certificate from KERN's accredited laboratory; it is available as an option with the product.

A certificate is not verification

However comprehensive the certificate, it does not turn a scale into a verified instrument. For selling by weight, medical weighing and the pharmacy the green M mark is required; see verification or calibration. Conversely, a verified scale does not automatically come with a certificate; if you want one, ask for it with the verification or re-verification.

What we supply

With a new scale, a certificate on the day of delivery, so your records start straight away; after that, periodic calibration with certificate on site or in our workshop; and for weights, recalibration in our own calibration laboratory, Masslab. How often is explained under how often should a scale be calibrated. The weights themselves are listed under check weights.

Frequently asked questions

Do I need a DAkkS certificate for ISO 9001?

Usually not. ISO 9001 requires traceable calibration at defined intervals; an ISO certificate from a service company using traceable weights meets that. An accredited certificate is needed if your own laboratory is accredited or a customer demands it.

What is the difference between a calibration certificate and a declaration of conformity?

The declaration of conformity belongs with the verification and states that the instrument complies with the directive. The calibration certificate states how much the instrument deviates, with the measurement uncertainty. They are two different documents for two different purposes.

How long is a calibration certificate valid?

A certificate describes the condition on the day of measurement and has no legal period of validity. The interval until the next calibration is set in your quality system.

Can I get a certificate for a scale I bought elsewhere?

Yes. We calibrate every brand, on site or in our workshop, and supply the certificate.