SI traceable hierarchy of small force at NISTIn order to realize the unit of force using the SI definition ofthe newton, the observed force must be expressed in termsof measured quantities that are themselves expressed in termsof some combination of the SI base units. Deriving a unitfrom realizations of the base units is typically the path ofleast uncertainty, but this need not always be the case. Forinstance, electrical forces may be measured in terms of the SIunit of length in combination with appropriate electrical units.Electrical units are themselves derived units in the SI, butthey may also be linked to practical representations of the voltand ohm based on the Josephson and quantized Hall effects.Because of this, they may be measured through a large dynami

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