The present thesis attempts at an overview of DC methods used for diagnosing electrical isolation systems. It investigates the problem of small currents and how to measure them. Part of the thesis deals with building a workstation designed for long-term monitoring of absorbing characteristics of dielectric materials and it also presents a layout of a workstation used for measuring recovery voltage. Both workplaces are computer-automated using the VEE Pro application provided by Hewlett-Packard. Tests were performed on both workstations and the obtained results were processed in a test report as specified under ČSN IEC 93. During the experiment, every effort was made to ensure and monitor the atmospheric conditions of the measuring process