BIPM technical services: Electrical Metrology

The most accurate electrical standards are the Josephson voltage standard and the quantum Hall resistance standard, both based on macroscopic quantum effects. These allow electrical units to be derived from two fundamental physical constants, the elementary charge and the Planck constant. With the revision of the SI in 2018, the numerical values of both constants have become fixed. As a consequence, the Josephson voltage standard has become a direct realization of the SI volt and the quantum Hall resistance standard of the ohm.

The BIPM uses both types of quantum standards as the basis for its measurement services in the field of electricity. The electricity laboratories provide comparison and calibration services to NMIs of Member States for the most fundamental electrical quantities: voltage, resistance and capacitance. This range of services underpins the infrastructure of the CIPM MRA by providing traceability to the SI for many smaller NMIs, and by allowing larger NMIs to demonstrate the equivalence of their own primary standards and to support their CMCs. For the comparison of NMIs’ primary electrical quantum standards with the lowest possible uncertainty dedicated travelling quantum standards have been developed by the BIPM. These are sent to the participating NMI and accompanied by BIPM staff for an on-site comparison. These comparisons can also be an occasion for knowledge transfer from the experienced BIPM scientists.