Discussion Forum

Accreditation and Quality Assurance

, Volume 16, Issue 3, pp 161-165

First online:

Some reflections on the proposed redefinition of the unit for the amount of substance and of other SI units

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Proposals on the floor at CIPM are aiming at defining basic units by stipulating a consensus value for a number of fundamental constants. The paper indicates the author’s viewpoint about a number of issues that, in his view, should be better understood before such a choice becomes indisputable. They include the count nature of the Avogadro number; the correct expression of its stipulated numerical value; the check for the consistency of the SI system; the shift to the unit of the experimental uncertainty; the loss of the concept of base unit; the possibility of checking the correctness of the future standards; implications for the future reductions in uncertainty; the meaning of ‘fundamental’ related to the constants; and some lexical problems.


Basic units Definition of units Fundamental constants SI