Abstract - Luca Callegaro

The International System of units (SI) is the basis of modern day measurements. In the SI in force until 2019, base units were defined in very different ways; the kilogram was defined as the mass of a single object, the international prototype - a cylinder of platinum-iridium alloy manufactured in 1889. The prototype is unique, at risk of damaging, nearly inaccessible (measured only about every 40 years) and there is some evidence of a change in its mass. On 16 November 2018 the General Conference of Weights and Measures has approved a major revision of the SI. All the seven base units are defined in terms of a fundamental constant of nature, which have an exact value. It is possible to realize the units everywhere and everytime, by probing with experiments these fundamental constants. Electrical units are defined in terms of the elementary charge e and the Planck constant h; it is possible to realize the volt, ohm and ampere by quantum experiments in solid-state devices. The kilogram, redefined in terms of h, can be realized by counting atoms in a silicon sphere, or linking it to the quantum realization of the electrical power unit, the watt. The redefinition was enforced on the implementation day: May 20, 2019.

Luca Callegaro was born in 1967. He received the M.Sc. degree in electronic engineering and the Ph. D. degree in physics from the Politecnico di Milano, Milan, Italy, in 1992 and 1996, respectively.

He joined the Istituto Nazionale di Ricerca Metrologica (INRIM), Turin, Italy, in 1996, where he is currently head of the Quantum Electronics Group. He has authored about 100 articles on international reviews and the book Electrical Impedance: Principles, Measurement and Applications (Taylor & Francis, 2012). His research interest is focus on electrical impedance metrology. He is responsible for the Italian National standards of electrical capacitance, inductance, ac resistance, and ac voltage ratio.

Dr. Callegaro is a member, and served four years as the Chair, of the Technical Committee for Electricity and Magnetism (TC-EM) of EURAMET, the European Association of National Metrology Institutes, and the Italian delegate to the Consultative Committee for Electricity and Magnetism (CCEM) of the International Committee for Weights and Measures (CIPM).