An SI for humans and a Digital-SI for machines

Abstract The international metrology community is focusing on the digitalisation of the International System of Units (SI). A digital SI does not necessarily have to be a digital version of the present International System of Units (SI) designed for communication between humans, or between humans and machines. This contribution reviews a proposed Digital System of Units (D-SI) for communication between machines using only the seven SI base units. We analyze the convenience of including in a future D-SI the conversion to the seven SI base units of most of the non SI units used worldwide for machine-to-machine communication, being machine accessible at the International Bureau of Weights and Measures (BIPM) website. This needs authoritative agreement of the corresponding conversion factors to be used. In this way, the dream of managing a single system of units could be achieved by machines before humans. Some causes of ambiguity in the present SI that may be overcome in the D-SI are also considered.