"Demonstration" vs. "designation" of measurement competence: the need to link accreditation to metrology

Formal acceptance of the results of chemical laboratories is increasingly organized through a) accreditation of measuring laboratories nationally and b) mutual recognition of accreditation internationally (through formal Multilateral Recognition Agreements, MRAs). However, real comparability of results of measurements is realized by using common (internationally agreed) measurement scales which make these results traceable to this scale, i.e. "traceable" to the same (internationally agreed) value of the unit of that scale. In addition, the criterion against which the evaluation is done, should be "external" to the measurement laboratories which are being evaluated. This is realized in IRMM's International Measurement Evaluation Programme (IMEP) where evaluation is performed against values which are anchored using "metrology", the science of measurement with its own rules, which offers a sound foundation for measurement in all scientific disciplines. It is argued in this paper that the demonstration of measurement capability against values on such scales provides a result-oriented rather than a procedure-oriented evaluation. Thus, competence can be "demonstrated" rather than just "designated" and this can be shown to both customers and regulators. It inspires more confidence.