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Planck Constant Determination from Power Equivalence



David B. Newell


Equating mechanical to electrical power links the kilogram, the meter, and the second to the practical realizations of the ohm and the volt derived from the quantum Hall and the Josephson effects, yielding an SI determination of the Planck constant. The NIST watt balance uses this power equivalence principle, and in 1998 measured the Planck constant with a combined relative uncertainty of 8.7 x 10-8, the most accurate determination to date. The next generation of the NIST watt balance is now being assembled. Modification to the experimental facilities have been made to reduce the uncertainty components from vibrations and electromagnetic interference. A vacuum chamber has been installed to reduce the uncertainty components associated with performing the experiment in air. Most of the apparatus is in place and diagnostic testing of the balance should begin this year. Once a combined relative uncertainty of one part in 10-8 has been reached, the power equivalence principle can be used to monitor the possible drift in the artifact mass standard, the kilogram, and provide an accurate alternative definition of mass in terms of fundamental constants
Proceedings Title
Abstract, Bulletin Amer. Physical Society
Conference Dates
April 28-May 2, 2000
Conference Location
Long Beach, CA


Planck, constant, fundamental constants, kilogram, watt, balance, mass, standard


Newell, D. (2000), Planck Constant Determination from Power Equivalence, Abstract, Bulletin Amer. Physical Society, Long Beach, CA (Accessed June 19, 2024)


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Created April 1, 2000, Updated February 19, 2017