Hao Fang

Bureau International des Poids et Mesures, Sèvres, Île-de-France, France

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Publications (7)6.84 Total impact

  • IEEE Transactions on Instrumentation and Measurement 07/2011; 60:2415-2421. · 1.71 Impact Factor
  • IEEE T. Instrumentation and Measurement. 01/2011; 60:2378-2386.
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    ABSTRACT: Since beginning the construction early in 2005, considerable progress has been made on the watt balance of the Bureau International des Poids et Mesures (BIPM). We have continued the development of a room-temperature version to test the feasibility of simultaneous force and velocity measurements. Preliminary measurements of the voltage-velocity ratio have been carried out with a reproducibility of the order of 1 part in 10<sup>4</sup>. The coil suspension has been improved to reduce the undesired coil movement in the 5 degrees of freedom different from a perfectly vertical movement. Further work on the current source has reduced its long-term drift to a few parts in 10<sup>9</sup> per minute with a satisfactory short-term stability. A technique needed to separate the voltage induced in the coil from the voltage drop due to the current flow based on the use of a second noninductive coil has been tested. The second coil is now being integrated into the apparatus. Work has started on the geometrical and magnetic characterizations of a large precision solenoid that will become the reference for the magnetic field alignment. The collaboration with a university on the fabrication of our magnetic circuit is being continued. This paper briefly outlines the main ideas of the BIPM watt balance and reports the progress to date.
    IEEE Transactions on Instrumentation and Measurement 05/2009; · 1.71 Impact Factor
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    The European Physical Journal Conferences 01/2009; 58:924-929.
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    ABSTRACT: The Bureau International des Poids et Mesures (BIPM) has recently started work on a watt balance to link the kilogram with the Planck constant, in view of a future redefinition of the kilogram. This paper presents the essential ideas of the BIPM watt balance and reports the progress to date
    IEEE Transactions on Instrumentation and Measurement 05/2007; · 1.71 Impact Factor
  • IEEE T. Instrumentation and Measurement. 01/2007; 56:538-542.
  • A. Picard, Hao Fang
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    ABSTRACT: Improved knowledge of air density will be useful to support various experiments in the mass field. A study was carried out at the Bureau International des Poids et Mesures to reduce the uncertainty on the air density determination by comparison of the performance of the following three methods: application of the CIPM- 81/91 formula; direct determination using air buoyancy artefacts having the same surface area but a large volume difference; refractometry, exploiting the high correlation between air density and air index of refraction, using a novel refractometer well adapted to our requirements (relative determination). The coherence among the three methods was satisfactory, but a discrepancy of the order of 10<sup>-4</sup> kg·m<sup>-3</sup> was observed between the CIPM-81/91 formula and methods employing artefacts. Additional measurements made in the framework of Euromet mass project 144 confirm this difference, which needs to be clarified by future studies using gravimetric measurements and on further investigations of the air composition.
    IEEE Transactions on Instrumentation and Measurement 05/2003; · 1.71 Impact Factor