SI changes the definitions of the kilo, ampere, kelvin and mole

On May 20, the revision of the International System of Units came into effect, evolving to adapt to global measurement requirements.

As of May 20, 2019, a kilogram is no longer a kilogram as we knew it. Coinciding with World Metrology Day, the revision of the International System of Units (SI) has come into force , in which the kilogram, ampere, kelvin and mole are redefined in terms of fixed numerical values of constants of nature and will inherit their associated uncertainties.

Image of the Spanish Metrology Center

The SI is a coherent system of units, which makes it possible to quantify any measurable quantity of interest in research, industry, commerce or society, in an infinite number of very varied fields. It was formally defined and established in 1960 and since then it has been partially revised several times in order to meet the needs of science and technology. This time, its revision has been more profound.

The result of this revision is a more coherent and fundamental definition of the entire SI, dispensing with practical realizations based on material artifacts, as was the case until now with the international prototype of the kilogram, with the possibility of loss and strong limitations of long-term stability, moving to more accurate practical realizations, as well as reproducible at any time and place.

Image of the Spanish Metrology Center

The use of constants of nature to define international units of measurement will enable the scientific community and industry to more accurately obtain and disseminate their measurements, from the smallest to the largest, thus meeting modern measurement requirements.

This change should serve to encourage the development of new standby technologies.