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A LEGO Watt Balance, An apparatus to demonstrate the definition of mass based on the new SI



Leon S. Chao, Stephan Schlamminger, David B. Newell, Jon R. Pratt, Georgio A. Sineriz, Frank C. Seifert, Darine El Haddad, Yusi A. Cao, Xiang Zhang


A redefinition of our system of units, the SI, is currently being discussed and its implementation is expected in 2018. With the redefinition, the current base units will no longer be required and all units henceforth will be based upon fixed values of seven reference constants. The watt balance is an apparatus that allows one to realize the kilogram from a fixed value of the Planck constant. At the National Institute of Standards and Technology, a watt balance at the kilogram level is currently under construction. For outreach purposes, we have constructed a LEGO tabletop watt balance, capable of realizing a gram size mass. This article presents the design, construction, calibration, and measurement of the LEGO watt balance with a full parts list in the Appendix. The experimental procedures and techniques to drive measurement accuracy at the gram-level to 1% are described in detail.
American Journal of Physics


watt balance, kilogram, gram, LEGO, mass, metrology


Chao, L. , Schlamminger, S. , Newell, D. , Pratt, J. , Sineriz, G. , Seifert, F. , El, D. , Cao, Y. and Zhang, X. (2015), A LEGO Watt Balance, An apparatus to demonstrate the definition of mass based on the new SI, American Journal of Physics, [online], (Accessed April 18, 2024)
Created October 20, 2015, Updated October 2, 2019