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In the past four years, we have constructed a new watt balance at the National Institute of Standards and Technology (NIST), with the goal to realize the unit of mass after the redefinition of the International System of Units, expected to occur in 2018. The new watt balance has been operational since the fall of 2015 and we describe our first measurements with it.
A redefinition of the International System of Units, the SI, is impending and could occur as early as 2017. After redefinition, a means to realize the unit of mass is required. A watt balance is a promising device to realize the unit of mass at the kilogram level. At the National Institute of Standards and Technology (NIST), construction of a new watt balance with the sole purpose to realize mass...
In 2013, a new measurement of the Planck constant h was performed using a watt balance at the National Institute of Standards and Technology (NIST). The value is h = 6.626 069 79(30) × 10−34 Js. The relative standard uncertainty of this determination is 45 × 10−9.
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