A quantum ampere

Abstract

The revision of the International System of Units (SI), implemented since 20 May 2019, has redefined the unit of electric current, the ampere ( A), linking it to a fixed value of the elementary charge. This paper discusses the new definition and the realisation of the electrical units by quantum electrical metrology standards, which every year become more and more accessible, reliable and user friendly.

Fundamentals of Measurement: Giovanni Giorgi and the International System of Units

“…The 1990 conventional units introduced, a century later, the very same problem of the 1893 practical international units [9]. Soon, new determinations of the Josephson and von Klitzing constant measured in terms of the SI units were published, and the 1989 values given above were updated, not only with improved accuracies, but also to different values.…”