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1.Joint Committee for Guides in Metrology, Working Group 2, International Vocabulary of Metrology—Basic and General Concepts and Associated Terms (VIM), 3rd ed. ( JCGM, Sèvres, France, 2008), p. 46.
2. F. Seifert, A. Panna, S. Li, B. Han, L. Chao, A. Cao, D. Haddad, H. Choi, L. Haley, and S. Schlamminger, “ Construction, measurement, shimming, and performance of the NIST-4 magnet system,” IEEE Trans. Instrum. Meas. 63, 30273038 (2014).
3. B. Kibble, “ A measurement of the gyromagnetic ratio of the proton by the strong field method,” in Atomic Masses and Fundamental Constants, edited by J. H. Sanders and A. H. Wapstra ( Plenum, New York, 1976), vol. 5, pp. 545551.
4. M. Stock, “ Watt balance experiments for the determination of the Planck constant and the redefinition of the kilogram,” Metrologia 50, R1R16 (2013).
5. T. Quinn, L. Quinn, and R. Davis, “ A simple watt balance for the absolute determination of mass,” Phys. Educ. 48, 601606 (2013).
6.Certain commercial equipment, instruments, and materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.
7. J. Clarke, “ The Josephson effect and e/h,” Am. J. Phys. 38, 10711095 (1970).
8. Y. Tang, V. N. Ojha, S. Schlamminger, A. Rüfenacht, C. Burroughs, P. Dresselhaus, and S. Benz, “ A 10V programmable Josephson voltage standard and its applications for voltage metrology,” Metrologia 49, 635643 (2012).
9. J. Eisenstein, “ The quantum Hall effect,” Am. J. Phys. 61, 179183 (1993).
10. R. E. Elmquist, M. E. Cage, Y.-H. Tang, A.-M. Jeffery, J. R. J. Kinard, R. F. Dziuba, N. M. Dziuba, and E. R. Williams, “ The ampere and electrical standards,” J. Res. Nat. Inst. Stand. Technol. 106, 65103 (2001).
11. T. Quinn, “ News from the BIPM,” Metrologia 26, 6974 (1989).
12. B. Taylor and T. Witt, “ New international electrical reference standards based on the Josephson and quantum Hall effects,” Metrologia 26, 4762 (1989).
13.National Oceanic and Atmospheric Administration, “ Surface gravity prediction by NGS software requests,” <>.
14.See supplementary material at for software, installation instructions, CAD file, and an alternative circuit diagram.[Supplementary Material]
15.We deliberately use V s/m as units for (BL)V, to emphasize that V is a conventional unit, while m and s are SI units. With the unit of T m we would have lost this distinction. Analogously, we use the unit N/A for the quantity (BL)F.
16. H. E. Swanson and S. Schlamminger, “ Removal of zero-point drift from AB data and the statistical cost,” Meas. Sci. Technol. 21, 115104115110 (2010).
17. R. L. Steiner, E. R. Williams, D. B. Newell, and R. Liu, “ Towards an electronic kilogram: An improved measurement of the Planck constant and electron mass,” Metrologia 42, 431441 (2005).
18. I. Robinson, “ Alignment of the NPL Mark II watt balance,” Meas. Sci. Technol. 23, 124012124029 (2012).
19. B. Kibble and I. Robinson, “ Principles of a new generation of simplified and accurate watt balances,” Metrologia 51, S132S139 (2014).
20. S. Knotts, P. Mohr, and W. Phillips, “ An introduction to the New SI,” e-print arXiv:1503.03496 [physics.ed-ph].
21. J. L. Lee, “The NIST Do-It-Yourself Watt Balance (Made With LEGO Bricks!),” Online video clip, 26 August, 2015, <>.

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A global effort to redefine our International System of Units (SI) is underway, and the change to the new system is expected to occur in 2018. Within the newly redefined SI, the present base units will still exist but be derived from fixed numerical values of seven reference constants. In particular, the unit of mass (the kilogram) will be realized through a fixed value of the Planck constant . A so-called watt balance, for example, can then be used to realize the kilogram unit of mass within a few parts in 108. Such a balance has been designed and constructed at the National Institute of Standards and Technology. For educational outreach and to demonstrate the principle, we have constructed a LEGO tabletop watt balance capable of measuring a gram-level masses to 1% relative uncertainty. This article presents the design, construction, and performance of the LEGO watt balance and its ability to determine .


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