Corona Charging and Current Measurement using Phi-type Corona Electrodes

摘要

In order to develop a non-contact surface resistivity measurement, corona charging of a test material under simultaneously measurement of a surface potential or an induction current caused by the traveling surface charge have been investigated using phi-type electrodes. The phi-type electrode consisted of a high voltage needle electrode that penetrates a circular hole of a grounded planar electrode. The phi-type electrode was positioned over electrically isolated test materials. The purpose of the design was to supply static charges on the test surface, to give a ground potential above the charged test material, and to measure the surface potential or the induction current caused by the propagated surface charge. The test materials with the surface resistivities of 10~6 to 10~(12) Ω were prepared by coating conductive polymer layers on the PVC disk. Two kinds of setup were prepared for higher surface resistivity (Model H) and lower surface resistivity (Model L). The Model H had a surface voltmeter to measure the slow propagation of surface charge. The rise time of the surface potential was linearly increased with the surface resistivity of 3×10~9 to 3×10~(12) Ω. The Model L had two induction probes to measure the fast propagation of the surface charge. The rate of total induction charges was a function of the surface resistivity of 3×10~6 to 3×10~9 Ω. The phi-type electrodes was found to be effective for non contact surface charge measurement of dissipative materials.