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Measuring 10 gram masses in terms of electrical quantities using a LEGO-based Kibble balance



Leon S. Chao, Stephan Schlamminger


In 2018, the International System of Units (SI) is expected to undergo a complete redefinition. This redefinition presents a paradigm shift where the present SI, based on seven fundamental units, will evolve into a system based on seven fundamental constants. More specifically, the unit of mass, the kilogram, will no longer be defined by an artifact standard, but rather be derived from a fixed value of the Planck constant h. One possible means to realize the unit of mass from h is provided by the watt balance (or Kibble balance), invented in 1975 by Dr. Bryan Kibble (1938-2016). Since the advent of his concept, many national metrology institutes around the world have worked toward developing watt balances capable of realizing a kilogram mass with relative uncertainties of a few parts in 10^8. At the National Institute of Standards and Technology (NIST), located in the USA, we have developed a high-precision, full-sized watt balance as well as a fun, tabletop watt balance constructed from LEGO bricks capable of measuring gram-sized masses with a relative uncertainty of 1%. This article presents the design, construction, and performance of the LEGO watt balance and its ability to measure a small mass.
Lab World Magazine


Chao, L. and Schlamminger, S. (2016), Measuring 10 gram masses in terms of electrical quantities using a LEGO-based Kibble balance, Lab World Magazine, [online], (Accessed June 22, 2024)


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Created September 1, 2016, Updated December 4, 2019