A simple and accurate resistance comparator with a long-scale ratiometric digital multimeter

This paper describes a resistance comparator, based on a long-scale digital multimeter, suitable for primary resistance metrology. The comparator measures the resistance ratio between two four-terminal standards from the readings of the multimeter, when operating in the voltage ratio mode. The quasi-simultaneous measurement of the resistors voltages strongly relaxes the stability requirements of the driving current source with respect to other published comparators, which are based on a shuttling voltage reading. Measurements between resistors of nominal value 12 906 Ω (the quantized Hall resistance) gree with a reference value, given by a dc current comparator bridge, within a few parts in 108.