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APS » Journals » Phys. Rev. Lett. » Volume 81 » Issue 12
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Phys. Rev. Lett. 81, 2404–2407 (1998)

Accurate Measurement of the Planck Constant

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Edwin R. Williams*, Richard L. Steiner†, David B. Newell‡, and Paul T. Olsen§,**
National Institute of Standards and Technology, Gaithersburg, Maryland 20899

Received 1 July 1998; published in the issue dated 21 September 1998

Using a moving coil watt balance, electric power measured in terms of the Josephson and quantum Hall effects is compared with mechanical power measured in terms of the meter, kilogram, and second. We find the Planck constant h = 6.62606891(58)×10-34Js. The quoted standard uncertainty (1 standard deviation estimate) corresponds to (8.7×10-8)h. Comparing this measurement to an earlier measurement places an upper limit of 2×10-8/yr on the drift rate of the SI unit of mass, the kilogram.

© 1998 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.81.2404
DOI:
10.1103/PhysRevLett.81.2404
PACS:
06.20.Jr, 06.20.Fn, 06.30.Dr

*Email address: firstname.lastname@nist.gov

†

‡

§Retired. Email address: tomolsen@tnaccess.com

**Electricity Division, Electronics and Electrical Engineering Laboratory, Technology Administration, U.S. Department of Commerce.

 
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