Surface potential of insulator plate equipped with a holed-grounded electrode charged by ion spray

Surface potentials of insulator plates charged by ion spray have been investigated to address a possible application for measuring surface resistance of insulators without any contact to the surface. The ion spray was supplied from a wire electrode with dc high voltage, passing through a meshed electrode with bias dc voltage, to the insulator surface tested. The insulator plate was equipped with a holed-grounded electrode not only to localize the region to be charged by the ion but also to provide a ground potential beneath the sprayed area for surface potential measurement. The magnitude of the surface potential of the charged insulator was adjusted by the magnitude of the bias voltage applied to the meshed electrode and the hole diameter of the grounded electrode. The time variations of the surface potential were measured after the charging for various insulator plates with different surface resistance. The decay time of the surface potential significantly depends on the surface resistance of the insulator surface. It was found that the holed-grounded electrode located beneath the insulator surface was significantly important for the surface potential measurement, which can apply to the non-contact surface resistance measurement.