Partenaires et organisations internationales
(Anglais)
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Physikalisch-Technische Bundesanstalt, Braunschweig (D), National Physical Laboratory, Teddington (UK), Instituto Elettrotechnico Nazionale 'Galileo Ferraris', Torino (I), Czech Technical University, Faculty of Electrical Engineering, Prague (CZ), Enterprise Ireland, National Metrology Laboratory, Dublin (IRL), Instituto Nacional de Engenharia e Tecnologia Industrial, Lisbon (P)
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Résumé des résultats (Abstract)
(Anglais)
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A new quantum standard for the calibration of capacitors was developed. The measuring system is based on the quantum Hall effect (QHE). It is capable of calibrating capacitance standards in the range 10 pF to 10 nF with a relative uncertainty of 10-7. Today, only a few European National Metrological Institutes (NMIs) are able to realise the capacitance unit with a relative uncertainty of 10-6 or better. The majority of the NMIs are obliged to link their capacitance metrology by means of travelling standards, thereby losing a factor of about ten in accuracy. The advantage of a quantum standard is that its value depends only on fundamental physical constants. Laboratories having access to the new quantum standard in the future will become independent and, more importantly, will be able to reduce the uncertainty of their capacitance calibrations by a factor of ten to one hundred. Capacitance standards are particularly important in the aerospace and the electrotechnical industry. The top industrial calibration laboratories are now at the point where it is not possible for them to reduce their uncertainties using existing equipment. As a consequence of the world-wide trend of decreasing uncertainties - a factor of ten every 20 years - new and improved techniques and equipment are necessary. The aim of this project was to concentrate the knowledge and experience of the seven partners and to collaborate in the development of an easy-to-handle modular AC quantum standard for the calibration of capacitors. Each of the self-contained modules (optimised AC quantum Hall samples, automated capacitance ratio bridge, automated quad-rature bridge, improved AC standards) constitutes a useful stand-alone instrument which can also be used for various applications outside the proposed system. Due to the modular construction, potential users may either rebuild the whole system or extend their existing facilities using some of the self-contained modules.METAS contributed to the project as follows:· A comprehensive and detailed study of the parameters influencing the characteristics of QHE devices used in metrology was carried out. A set of recommendations was established which will help to improve the quality of QHE devices made for metrological applications in the future.· A QHE sample holder for AC measurements was developed. It is already in use in different laboratories around the world. The standardisation of this important piece of equipment facilitates the sample exchange and increases the synergy between NMIs. A closer collaboration between NMIs in this field will certainly result in a better understanding of the QHE and its application in impedance metrology.· A 12.906 kW AC transfer standard was developed. The device has a modular design which facilitates the modification of the nominal value of the resistor. The standard is commercially available and can be used for various applications in impedance metrology.Publications- B. Jeckelmann, A. Rüfenacht, B. Jeanneret, F. Overney, K. Pierz, A. von Campenhausen, G. Hein, 'Optimization of QHE-devices for Metrological Applications', IEEE Trans. Instrum. Meas. 50 (2), pp. 218-222, 2001.- B. Jeckelmann and B. Jeanneret, 'The quantum Hall effect as an electrical resistance standard', Rep. Prog. Phys. 64, pp. 1603-1655, 2001.- J. Melcher, J. Schurr, K. Pierz, J.M. Williams, S.P. Giblin, F. Cabiati, B. Jeckelmann, B. Jeanneret, F. Overney, J. Bohácek, J. Riha, O. Power, M. Nunes, M. Lobo and I. Godinho, 'The European AC-QHE Project: Modular system for the calibration of capacitance standards based on the quan-tum Hall effect', submitted to the Conference of Precision Electromagnetic Measurements (CPEM), Ottawa June 2002.
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