The UME Kibble balance project was initiated at the second half of 2014. During this period we have studied the theoretical aspects of Kibble balances in which an oscillating magnet generates AC Faraday's voltage in a stationary coil and constructed a trial version to implement this idea. The remarkable feature of this approach is that it can establish the link between the Planck constant and a macroscopic mass by one single experiment in the most natural way. Weak dependences on variations of environmental and experimental conditions, small sizes and other useful features offered by this novel approach reduce the complexity of the experimental setup. This paper describes the principles of oscillating magnet Kibble balance and gives details of the preliminary Planck constant measurements. The value of the Planck constant determined with our apparatus is with a relative standard uncertainty of 6 ppm.

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The UME KB-3 operating since 2020 allows the realization of kilogram under ambient air conditions owing to its distinguishing design and operation protocol. This is possible only because the coil pair is stationary but the surrounding magnet assembly is moving. The mechanically decoupled nature of the magnet assembly allows the implementation of a local vacuum for displacement measurements rather than a vacuum covering the entire apparatus. The balance operates in single mode with simultaneous operation of weighing and moving phases instead of successive phases. A novel dynamical measurement procedure is developed in order to conform with the single phase measurements. The paper describes the apparatus and presents the measurement results for stainless steel mass artefact with a nominal value of 1 kg. The mass of the artefact is measured with a total relative uncertainty of 54 ppb.

<p>The redefinition of the kilogram in terms of Planck constant came into effect on 20 May 2019. The National Metrology Institute of Turkey (UME) realised the new definition by means of the oscillating magnet Kibble balance. The novel dynamical measurement procedure developed for Kibble balance in Turkey has the advantage of being less sensitive to environmental disturbances compared to the traditional Kibble balance experiments. Precise displacement measurements are performed either with Michelson or Fabry-Perot interferometers in worldwide Kibble balances. Moreover, most of them operate in a global vacuum. A commercial Michelson interferometer has been used in UME’s Kibble balance experiment. In this article, we determine the contribution of ultra-small oscillations to the Planck constant by taking simultaneous displacement measurements on two back-to-back mirrors attached to the piezoelectric transducer, undergoing an oscillatory motion with the Michelson and Fabry-Perot interferometers. The following novel measurement procedure makes such measurements possible in a regular laboratory environment. Otherwise, the experiment needs to be performed in a global vacuum. This is why we were required to investigate the resolution performances of these devices in laboratory conditions. As the expected relative uncertainty in the redefinition of kilogram is above the resolution uncertainties of both interferometers, we may conclude that a commercial Michelson interferometer will serve our purposes in our route to the redefinition of a kilogram by means of local vacuum.</p>

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