Current Divider Based Impedance Comparator

The paper describes an ac impedance measurement comparator system which uses a current divider (or splitter). The divider makes use of a current comparator whose windings are connected in a way such as to allow the splitting of a single current signal in two components with very accurate ratio to be attained. Each current component flows through impedances to be compared. Preliminary investigations indicate that such an arrangement is able to provide very accurate impedance measurements with errors of parts in \pmb10⁶ or even smaller. Resolutions of parts in \pmb10⁹ were also experimentally achieved. Since the system uses a single ac current source, inherent current instabilities of the source cause negligible effects on differential voltage measurements, what alleviates requirements on the ac source. Digital sampling can easily be implemented with the system for speeded-up and automated impedance comparisons.