The New METAS Joule-Kibble Balance - a Realisation of the Kilogram
The University of Bern, School of Biomedical and Precision Engineering SBPE and the Federal Institute of Metrology METAS are collaborating on the development of a new Kibble balance which will include the principle of a Joule balance.
Until 2019 the kilogram was the last base unit of the International System of Units (SI) still based on an artefact: the international prototype of the kilogram K which is kept at the Bureau International des Poids et Mesures (BIPM). Each country, signatory of the Meter Convention, received a copy of K, as national prototype of the kilogram (Fig. 2)
Following the decision of the 26th General Conference on Weights and Measures, the International System of Units is nowadays fully defined in terms of a set of seven constants. As a consequence, the unit of mass, the kilogram, is linked to a fixed value of the Planck constant h since 20 May 2019. Today, two experiments allow the realization of this link: on the one hand, the x-ray crystal density method and on the other hand, the watt balance also known as Kibble balance.
In strong partnership with external partners, coming from universities, research institutes or industry, METAS developed a Kibble balance. To bring the experiment to the next level, a new project has been initiated with the aim of reducing the uncertainty by combining different experimental and theoretical approaches.
