Adaptive current sources and feedback applied to the cryogenic current comparator

We present a novel current source for the cryogenic current comparator resistance bridge which is adaptable to many coil, resistance and filtering configurations. To achieve optimum performance of the system both current feedback from the SQUID and feedback from the voltage detector are examined and incorporated into the design. The properties of the new design are improved flux tracking, leakage, and flexibility without comprising the self checking capability and accuracy. The system has been used at the NRC over the resistance range of 1 /spl Omega/ to 1 M/spl Omega/.<
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