Upscaling DC resistance using a Josephson junction array

A ratio standard for DC resistance measurements in the range above about 10 kΩ using a three-terminal Josephson junction series array is described. Resistance ratios of two-terminal resistors from 1:1 to at least 1:10 are examined with a single device utilizing the voltage steps of the Josephson array as voltage sources of a potentiometer bridge configuration. Some features of the circuit are discussed. The system promises systematic ratio errors below 10^-8 and uncertainties which depend only on the quality of the resistors. Preliminary measurements with a prototype instrument show a relative reproducibility of 1×10^-7, limited by the noise of a commercial digital multimeter used as a detector