Milligram mass metrology using electrostatics

Although mass has historically been defined using an artifact standard, other means of realization are possible. One alternative approach employs a precision electromechanical balance to derive a force based on electrical units, which is used to measure the weight of a mass artifact. The National Institute of Standards and Technology (NIST) Electrostatic Force Balance (EFB) incorporates voltage, displacement and capacitance measurements that are traceable to the International System of Units (SI), allowing the traceable measurement of electrostatic force that can be used in conjunction with local gravity to arrive at mass. This article briefly describes this weighing process, its associated uncertainty, and context within the impending redefinition of the SI.