4. Recognition for reference materials

Where external calibration services are used, traceability of measurements must be ensured by the calibration services of laboratories able to demonstrate their competence and suitability in terms of measurement and traceability. Calibration certificates issued by these laboratories must contain the measurement results, including the uncertainty of measurement and/or a declaration of conformity to an identified metrological specification. A certificate bearing the symbol of an ILAC MRA signatory accreditor therefore meets this requirement.

It is, however, more difficult to obtain this declaration from an external service provider, unless the user's acceptance criteria for the equipment in question are provided. Many users are reluctant to pass on these documents because of the confidential information that could be extracted from them. Compliance with these specifications...