AC QHE-based calibration of resistance standards

A coaxial transformer bridge for QHE-based calibration of resistance standards has been developed. An eight-decade two-stage inductive voltage divider forms ratio arms of the bridge and triple-series connection of the reference QHE sample to the bridge is employed. Frequency characteristics of LEP heterostructures have been measured by comparing them against resistors with calculable frequency dependences. Two quadrifilar, Gibbings´s type resistors with nominal values of 12 906 /spl Omega/ and 6353 /spl Omega/ have been used in this measurement.