The construction of an apparatus for electrochemical investigations using an IBM personal microcomputer is presented. This apparatus can be used in a wide range of electrochemical methods, stationary and dynamic. A special construction solution allows for application in electrochemical impedance spectroscopy measurements, particularly using the fast Fourier transform method. The apparatus contains a potentiostat connected with signal generators for the polarization of the working electrode and two identical analogue-to-digital conversion channels. For data transmission between this apparatus and the microcomputer, two parallel transmission ports and a special communication interface are used. Also, the detailed description of the construction of the analogue-to-digital conversion channels, including a special module for direct voltage compensation in the input analogue signal, is given, together with the final technical specification of the apparatus.