The NIST Watt Balance: Recent Results and Future Plans

Published

March 1, 1999

Author(s)

David B. Newell, Richard L. Steiner, Edwin R. Williams

Abstract

The last remaining SI base unit defined by an artifact is the kilogram. The NIST watt balance has been designed to measure the ratio of mechanical to electrical power, linking the artifact kilogram, the meter, and the second to the practical realizations of the ohm and the volt derived from the quantum Hall effect and the Josephson effect. Our recent results¹ set an upper limit of 2 x 10^-8/yr on the drift rate of the kilogram. By assuming the Josephson and von Klitzing effects are exact, we also determine the Planck constant h = 6.62606891(58) x 10^-34 Js. Modifications to the experiment and facilities are being made to achieve the next goal: providing an alternative kilogram definition in terms of fundamental constants.

Citation

Bulletin of the American Physical Society

Issue

1

Pub Type

Journals

Keywords

fundamental constant, kilogram, mass drift, planck's constant

Citation

Newell, D. , Steiner, R. and Williams, E. (1999), The NIST Watt Balance: Recent Results and Future Plans, Bulletin of the American Physical Society (Accessed May 28, 2025)