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 ΔV was measured. Repeated measurements of C = Ne/ΔV with this method have a relative standard deviation of 0.3 × 10$^{-6}$. This standard offers a natural basis for capacitance analogous to the Josephson effect for voltage and the quantum Hall effect for resistance.