Automatic compensation system for impedance measurement

This paper deals with the realization of the four-pair terminal definition of impedance standards. A simple though reliable system is described that allows an automatic compensation of the voltage at the low potential port of impedance standards to be obtained. Such a system, which employs a commercial DAQ board and an arbitrary signal generator, is controlled through a standard PC that implements the demodulation and the control algorithms. Preliminary tests have been performed in the frequency range of 50 Hz to 20 kHz with different kinds of impedance standards (resistive, inductive and capacitive), obtaining a residual voltage at the low potential port of less than 5 /spl mu/V.