Contributions of precision engineering to the revision of the SI
Stephan Schlamminger, Harald Bosse, Horst Kunzmann, Jon R. Pratt, Ian Robinson, Michael de Podesta, Paul Shore, Paul Morantz
All measurements performed in science and industry are based on the International System of Units, the SI. It has been proposed to revise the SI following an approach which had already been implemented for the redefinition of the unit of length, the metre, in 1983, namely to define the SI units by fixing the numerical values of a set of so-called defining constants, including c0, h, k, e and NA. We will discuss the reasoning behind the revision of the SI, which will likely be put into force in 2018. Precision engineering was crucial to achieve the required small measurement uncertainties and agreement of measurement results for the defining constants.