A test system and data analysis procedure are provided for use in electrophotographic printing with a whole set of characteristics determined to be important for efficiency and high quality images. The test system and data analysis procedure characterize dielectric relaxation processes in materials in terms of charge transport parameters that may include intrinsic charge density, charge mobility, and charge injection from the contact surfaces. The materials may include photoconductive drums or belts, charging rolls, developer rolls, intermediate transfer belts and output media such as paper transparencies or textiles. The apparatus consists of a charging source, a voltage detector and a current detector in an open-circuit mode of measurement. The configuration closely simulates the actual application of the materials in electrophotography and thus, can yield information more relevant for the applications.