Non-contact surface charge density profiles measurement on top and bottom of a charged film

Equivalent surface charge density profiles on the top and bottom surfaces of corona-charged films were measured using a surface potential voltmeter with a horizontal resolution of about 2 mm and a laser displacement meter with a vertical resolution of 10 mu m. A personal computer controlled the sample position with a resolution of a few tens of microns. The resolution was determined by the digital X-Y stage and the distance of the backside ground electrode from the bottom of the charged film. Surface potential profiles at several positions between the ground electrode (back) and the sample film were recorded, and the equivalent surface charge density profiles on the top and the bottom of the film were calculated and plotted automatically. Some interesting electrostatic phenomena related to the charge behavior of the films are reported: for example, the back side surface charge was affected by the surface discharge even if no ground electrode was nearby.<>