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Hysteresis and Related Error Mechanisms in the NIST Watt Balance Experiment



J. Schwarz, Ruimin Liu, David B. Newell, Richard L. Steiner, Edwin R. Williams, Douglas T. Smith, A Erdemir, J Woodford


The NIST Watt Balance experiment is being completely rebuilt after its 1998 determination of the SI Volt and Planck's constant. That measurement yielded a result with approximately 1 x 10-7 standard relative uncertainty. Because the goal of the new incarnation of the experiment is a ten-fold improvement in accuracy, it has been necessary to re-examine many sources of systematic error. Hysteresis effects account for a substantial portion of the projected error budget. They arise from mechanical, magnetic, and thermal sources. The new experiment incorporates several improvements in our apparatus to address these issues, including: stiffer components for transferring the mass standard on and off the balance; better servo control of the balance, better pivot materials; the incorporation of erasing techniques into our mass transfer servo system. We have carried out a series of tests of hysteresis sources on a separate system, and apply these results to our apparatus. The studies presented here suggest that our improvements can be expected to reduce hysteresis signals by at least a factor of 5 - perhaps as much as a factor of 50 - over the 1998 experiment.
Journal of Research (NIST JRES) -


DLC coating, hysteresis, Josephson constant, kilogram artifact, Planck's constant, Watt balance


Schwarz, J. , Liu, R. , Newell, D. , Steiner, R. , Williams, E. , Smith, D. , Erdemir, A. and Woodford, J. (2001), Hysteresis and Related Error Mechanisms in the NIST Watt Balance Experiment, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed April 24, 2024)
Created February 15, 2001, Updated October 12, 2021