Traceability is characterised by six essential elements
- An unbroken chain of comparison. An unbroken chain of comparisons originating at national or international standards of measurement and ending with the comparison of the local working reference standard and the unit under test.
- Measurement uncertainty. The measurement uncertainty for each step in the traceability chain must be calculated according to defined methods and must be stated at each step of the chain so that an overall uncertainty for the whole chain can be calculated.
- Documentation. Each step in the chain must be performed according to documented and generally acknowledged procedures and the results must be documented, i.e., in a calibration or test report.
- Competence. The laboratories or bodies performing one or more steps in the chain must supply evidence of technical competence, e.g., by demonstrating that they are accredited by a recognised accreditation body.
- Reference to SI units. Where possible, the primary national, international or intrinsic standards must be primary standards for realisation of the SI units.
- Recalibrations. Calibrations must be repeated at appropriate intervals in such a manner that traceability of the standard is preserved.
All instruments and artefacts used in the factory calibration of Renishaw XL-80 and ML10 laser systems and QC10 ballbars are fully traceable to UKAS accredited laboratories and thus to national standards. Traceability data (artefacts used and calibration details) are included on each certificate and flow charts illustrating the traceability process are also available for customer information.
Mutual Recognition
Whilst laboratory accreditation to an ISO standard (eg ISO17025) can verify the capability of a laboratory to produce measurement results that are traceable to appropriate stated references (usually measurement standards maintained by the national metrology institute (NMI) of the laboratory's home country), it does not explicitly relate to the equivalence of traceability of measurement results to standards maintained by one NMI versus another.
However, because NPL is accredited by UKAS (which is a signatory to the CIPM Mutual Recognition Agreement (MRA) then the validity of NPL’s standards and of their calibration and measurement certificates is recognised by all major National Metrology Institutes . (e.g. LNE: France; NIST: USA; PTB: Germany, NIM: China) whose national accreditation bodies are also signatory to the MRA.
Please refer to attached document download "Support Note 003" for further details of mutual recognition.
A measurement is said to be "traceable" if it can be related back to other identified reference standards, (usually national or international standards) through an unbroken chain of comparisons, with each step in the chain having stated uncertainties.