Basic passive electrical standards

The realization and reproduction of the farad, henry and ohm by national metrology institutes (NMIs), and in particular in France by the Bureau national de métrologie (BNM) [R 60] , requires the use of special resources. The volt and the ampere, in line with the current practical sequence of electrical units, are the subject of article .

The calculable capacity standard is a mechanical device based on an electrostatic theorem. It has the particularity of ensuring both the SI (International System) realization of the farad and the reproduction, or conservation, of this unit. In addition, inductance standards are connected to this primary standard, thus ensuring the SI realization of the henry.

The ohm is materialized and maintained by a phenomenon in the quantum physics of condensed matter. This is the quantum Hall effect. This is also the case for the volt, with the alternating Josephson effect (see ). These phenomena have truly revolutionized electrical metrology, since the resistances and voltages derived from them are related to the fundamental constants h/e ² and 2e/h respectively, where h is Planck's constant and e is the electron's charge. Under certain conditions, these phenomena provide fundamental standards [R 50] whose values are immutable in space and time.

However, this value of h/e ² needs to be known as accurately as possible, and therefore requires SI realizations of the resistance, hence the interest of the calculable capacitance standard, which enables direct determination of the ohm by means of a comparison of capacitance and resistance impedances. What's more, the results derived from these measurements are compared with those from different experiments involving not only h/e ² but also other fundamental constants.

The transfer of electrical units to users, or in other words, the traceability of electrical quantities to SI primary standards, is ensured by periodic calibration of hardware standards. These secondary...