The role of fundamental constants in the International System of Units (SI): present and future

This paper addresses the role of fundamental constants in (1) the current definitions of the SI base units; (2) practical representations of SI electric units and the consistency of those representations with the SI as deduced from the 1998 CODATA recommended values of the constants; and (3) redefinition of the kilogram and the impact on realizations of SI electric units of a newly proposed definition that fixes the value of the Planck constant h.