AccuBridgeTM A SELF CALIBRATING DC CUREENT COMPARATOR RESISTANCE BRIDGE

An optimized room temperature resistance bridge (AccuBridgeTM), modeled after the cryogenic current comparator, has been developed to determine current ratio’s with the highest accuracy. The direct current comparator has been optimized to reduce the leakage effects of the comparator. In addition, new self calibrating direct current sources have been fabricated and tested. AccuBridgeTM relies on self calibrating current sources, the self calibrating direct current comparator and self calibrating nanovoltmeter to achieve its accuracy. AccuBridgeTM makes use of its self-calibrating directcurrent-comparator to measure and compare accurately the ratio of the two resistors. A detailed description of AccuBridgeTM is presented with an analysis of its accuracy limitations with accuracies < 0.02 ppm and noise levels of <0.005 being achievable. The bridge is particularly suited to the scaling of resistance standards from 100KΩ down to 0.1Ω at the primary level, while offering a method for providing directly traceable ratio calibrations of less accurate current comparator resistance ratio bridges.