Calibration of 10 nF capacitance standard from DC quantum Hall resistance using a digital impedance bridge

This paper describes the calibration of a 10 nF capacitance standard traced to the DC quantum Hall resistance primary standard using a multi-purpose digital impedance bridge. The bridge can directly compare the unlike impedances in the fully digital (FD) mode, so the capacitance standard can be calibrated by a direct comparison against the AC resistance standard. The measurement ability of the bridge in the FD mode was evaluated in various angles, and the bridge voltage dependencies were improved by selecting appropriate impedances for the high current arms and also by using an additional injection circuit. Thereby, the measurement accuracy could reach up to 10(-7) in relative terms. Based on the bridge evaluation, a 10 nF capacitance standard was calibrated against a 10 k omega resistance standard, and the measurement value agreed with a reference value in the level of 10(-7).