6.5 Metrological Traceability

6.5.1 Establishing Metrological Traceability

The laboratory shall establish and maintain metrological traceability of its measurement results by means of a documented unbroken chain of calibrations, each contributing to the measurement uncertainty, linking them to an appropriate reference.

Note:

In ISO/IEC Guide 99, metrological traceability is defined as the “property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty.”

Note:

See Annex A for additional information on metrological traceability.

6.5.2 Traceability to the International System of Units (SI)

The laboratory shall ensure that measurement results are traceable to the International System of Units (SI) through:

  • Calibration provided by a competent laboratory.

    Note:

    Laboratories fulfilling the requirements of this document are considered to be competent.

  • Certified values of certified reference materials provided by a competent producer with stated metrological traceability to the SI.

    Note:

    Reference material producers fulfilling the requirements of ISO 17034 are considered to be competent.

  • Direct realization of the SI units ensured by comparison, directly or indirectly, with national or international standards.

    Note:

    Details of practical realization of the definitions of some important units are given in the SI brochure.

6.5.3 Alternative Metrological Traceability

When metrological traceability to the SI units is not technically possible, the laboratory shall demonstrate metrological traceability to an appropriate reference, e.g.:

  • Certified values of certified reference materials provided by a competent producer.
  • Results of reference measurement procedures, specified methods, or consensus standards that are clearly described and accepted as providing measurement results fit for their intended use and ensured by suitable comparison.