The fundamental requirements of a diagnostic procedure composed by defect identification, noise and disturbance rejection, separation of multiple sources, set-up conditions and test prescriptions, are described in this paper. This procedure allows to overcome problems found when practical objects are tested using the apparent charge measurement approach according to Std.IEC 60270. Definitions, methodologies and validation procedures relevant to the different diagnostic steps, are presented and discussed considering also a possible future development of fully automated instruments.
