AC RESISTANCE BRIDGE BASED ON THE CRYOGENIC CURRENT COMPARATOR

This paper describes a low-frequency ac resistance bridge based on a C ryogenic Current Comparator (CCC), The bridge is a main tool for resis tance traceability of 10 k Omega, 100 Omega, and 1 Omega to the quantu m Hall resistance (QHR), The bridge is typically operated with a PC ge nerating a sinusoidal ac signal ranging from (0.1 to 2) Hz, Using a ve ctor analyzer as a signal source the bridge is used to 1 kHz, Both sin usoidal and pseudo random signals have been used to compare the freque ncy dependence of standard resistors against the QHR. At present the b ridge can be used to perform accurate calibrations to 10 Hz, at higher frequencies the self-resonance of the CCC increases the uncertainty.