Direct determination of capacitance standards using a quadrature bridge and a pair of quantized hall resistors

摘要

We describe measurements made using a quadrature bridge to simultaneously compare two quantum Hall resistors (QHRs) with two 10 nF capacitors at 1233 Hz. This direct approach eliminates uncertainties due to thermal and structural instabilities and to ac/dc differences of the wire resistors normally used with an ac ratio bridge as an intermediary stage.