A Microcomputer has been employed for the automation of two types of measurements: Ellipsometry, and ac impedance in a wide frequency range (“network analysis”). These measurements are combined in the characterization of electrochemical interfaces. An identical simple and fast algorithm has been employed in both cases for the digital analysis of a sinusoidal signal. The rotating analyzer ellipsometer has a time resolution of 0,01 sec and a precision of 0.01 deg, following 1 sec integration time. The network analyzer generates a complex plane plot in the range of 10mHz-1kHz in 5 min. These specification have been achieved by employing only basic electrochemical instrumentation and a manual el1ipsometer, in conjunction with a low cost microcomputer.