This is our high end system for the frequency range from 3 μHz - 20 MHz (12.5 decades) based on the Alpha-A modular measurement system for dielectric, conductivity, electrochemical and impedance spectroscopy with several test interfaces. The sample impedance is directly determined by the phase-sensitive measurement of the sample voltage and current at fixed frequency. In combination with the ZGS active sample cell interface, the standard sample arrangement is a parallel plate capacitor with diameters from 40 mm to 10 mm and a spacing between the plates from 20 mm to 10 μm.