For a measurement to be documented, the measurement result must be traceable. Traceability is a quality of a measurement result or of the value of a standard that allows the result or value to be related to a reference (usually a national or international standard) through an unbroken chain of comparisons, each with stated uncertainties.
In connection with quality assurance under the ISO 9000 series or ISO 17025, measuring equipment must be traceable. In practice, this means ensuring that measuring equipment is calibrated, at defined intervals, by a laboratory that holds the national standard, or by a laboratory whose references are in turn calibrated against the national standard. There may be several links in this chain, as long as the measurement result for each step is documented with its associated uncertainty.
In principle, there are three options:
In connection with the accreditation of laboratories, calibrations must be performed either by an accredited calibration laboratory or by a national laboratory.
In the context of company certification, the practice is less strict, and requirements for traceability vary somewhat from case to case. Anyone seeking to establish traceability for their equipment should nevertheless assess which parameters or equipment are most critical for the process they wish to control, and allocate resources accordingly.
If you choose to have your equipment calibrated at the National Laboratory, this will satisfy the requirements of both accreditation bodies, certification bodies and regulatory authorities.
Metrological traceability in business and public administration is achieved through two main routes:
Legally regulated area
Measurements and measuring systems used in trade and industry are supervised by the Supervision Department of the Norwegian Metrology Service, which maintains traceability of its instruments to national standards and SI units. Enterprises then receive confirmation that their measuring equipment provides results within approved limits.
Voluntary area
Enterprises may establish voluntary traceability through accredited testing and calibration laboratories to national standards and SI units. During calibration, enterprises are provided with calibration values (estimates of deviation from the true value) and measurement uncertainty.
