This work describes an innovation of traditional systems used inC–VandG–Vcurve measurements. Although this system has been specifically developed to be used in the characterization of hydrogenated amorphous silicon (a‐Si:H), it is useful when information about conductance (G) or capacitance (C) frequency dependence is needed. The highlights of the new system are signal heterodination and microprocessor‐based digital control over current range and modulation frequency. The outstanding advantages of this system are significant reduction of operation time and more reliable measurements. Additionally, there is no waste of computer time in the control of data‐acquisition operations. The system has an excellent signal‐to‐noise ratio, a nearly infinite line signal rejection, and a broad frequency range of operation (20 to 105Hz).