RESISTANCE RATIO BRIDGE USING CRYOGENIC CURRENT COMPARATOR WITH DC-SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE MAGNETOMETER

A resistance ratio bridge using a cryogenic current comparator (CCC) w ith a de superconducting quantum interference device (dc-SQUID) was de veloped. Its structure, driving circuit and principle of operation wer e based on those of a resistance ratio bridge using a CCC with a comme rcially available rf-SQUID. Because of the small intrinsic noise of th e dc-SQUID, its resolution was determined not by the dc-SQUID noise bu t by the thermal noise of the resistor being tested. The ratio of a re sistor having a nominal resistance of 100 Omega and a resistor with th at of 1 Omega was measured with an uncertainty of 1.1 x 10(-8).