A quadrature bridge for QHE-based calibration of capacitance standards

A method is described which utilizes a 12906.4 /spl Omega/ resistor as a reference standard for capacitance calibrations. DC value of this resistor being obtained by comparing it against a quantum Hall effect device, its frequency dependence is measured by 1:1 comparison against a resistor having calculable frequency performance. Subsequently, the reference resistor and a 10 nF capacitor are linked by means of a quadrature bridge based on a commercial two-phase generator. The 10 nF capacitor, in turn, serves as a reference standard for calibration of capacitors of lower values by means of a four terminal-pair transformer bridge. By means of the quadrature bridge, capacitance can be measured with a standard uncertainty of less than 3 parts in 10/sup 5/ in the frequency range from 400 Hz to 5 kHz at the 10 nF level.