Precision measurements of elementary charge and the redefinition of the ampere

On 1 January 1990, to establish worldwide uniformity in the measurement of voltage and resistance and other electric quantities, the International Committee for Weights and Measures (CIPM) introduced new practical representations of the volt (V) and ohm (Ω) based, respectively, on the Josephson effect and quantum Hall effect, as well as the conventional (i.e. adopted) values of <em<K</em<<sub<J</sub< and <em<R</em<<sub<K</sub<. This paper gives the self-consistent set of the basic constants of electric quantities recommended in 2014 by the Committee on Data for Science and Technology (CODATA).