Electric-potential-measurement-based methodology for estimation of electric charge density at the surface of tribocharged insulating slabs

The auto-compensated electrostatic induction probe (ACEIP) is widely used for measuring the electric potential at the surface of conductive or insulating bodies. The aim of this paper is to elaborate a methodology for using this probe in view of performing the estimation of electric charge density at the surface of tribocharged insulating slabs. In such cases, the electric potential is not uniformly distributed on the surface under investigation. Metallic plates trimmed with different shapes were used to characterize the probe. Thus, a first series of experiments enabled a crude evaluation of the shape and size of the area “seen by the probe”: a 10-mm-diameter circle. Other experiments served to determine the transfer function that relates the value measured by the probe to the potential of a small area of constant electric potential located at a well-defined distance from it. By dividing the surface under investigation into a large number of small elementary areas, it was possible to use this transfer function to express the potential measured by the ACEIP as the sum of the contributions of each such element. An inverse matrix computation method enabled the estimation of the actual surface electric potential. Based on the results of a final set of experiments, the distribution of the electric charge density was estimated for slabs charged by corona-respectively triboelectric-effect.