A capacitance standard based on counting electrons

A capacitance standard based directly on the definition of capacitance was built. Single-electron tunneling devices were used to place N electrons of charge e onto a cryogenic capacitor C, and the resulting voltage change DeltaV was measured. Repeated measurements of C = Ne/DeltaV with this method have a relative standard deviation of 0.3 x 10(-6). This standard offers a natural basis for capacitance analogous to the Josephson effect for voltage and the quantum Hall effect for resistance.