156 / 2019-03-09 04:28:10

Remarks on the revised SI System

revised SI, base unis, physical constant

全体主题 > Calibration, Metrology and Standards

The revised SI (SI of 2018) is the long-time awaited system of units in which the standards of units dependent on material properties have been replaced by the standards based on physical constants and quantum effects. The redefinition of the SI system on the base of physical constants is its great advantage. However, the revised SI system is understood rather by narrow community of scientists and experts of metrology, not by a wide population of users. In particular this remark relates to the definitions of the kilogram and the kelvin in the SI. Critical remarks on the new SI concern sophisticated definitions, the set of base units and high costs of implementation the definition of the kilogram. The definitions of the base units don`t define anything. They only repead the physical constants. New standards of the kilogram (watt balance or XRCD method) are at least 30-50 times more expensive than the “old” standard – the artefact of PtIr alloy. In result, only about 10 national metrology institutes in the world are able to install and operate new standards of the kilogram. Before and after adopting the revised SI there are the proposals to replace the ampere, the base unit, by the wolt (or the ohm), thw kelvin by the joule, and the unit of mole by a new unit of amount of substance (Leonard`s proposal).