A digital quadrature bridge for impedance measurements

This paper describes a digital alternating current (ac) quadrature bridge for impedance measurements under development at INMETRO. This bridge is primarily intended to allow the comparison of ac resistors with standard capacitors but it could be applied to a myriad of impedance-measurement tasks as the precise determination of dissipation factor of capacitors, of resistor time-constants, as well as an aid in investigations on the nonlinear behavior of passive electronic components. Aimed at attaining measurement uncertainties of around 10 μΩ/Ω at 1 kHz under sinusoidal conditions, it has prospects for further improvements.