Conventional measurement techniques for the investigation of the behavior of corona‐charged polymer foil electrets allow one to determine the equivalent surface charge and the surface potential decayaftertermination of the charging process. This paper describes a technique which determines charges, currents, and potentialsduringthe charging process. The application of this technique to Teflon and polyethylene foils show the usefullness of the method. The values of transit times and of the trap‐modulated mobility for polyethylene are obtained.