METHOD AND APPARATUS FOR MEASUREMENT OF SURFACE CHARGE OF AN ELECTRET

摘要

Electret surface charge is measured accurately and in a reproducible fashion by supporting an electret between fixed electrodes positioned at a finite distance from the electret, one at ground potential and the other employed as a voltage probe. A conductive shutter is interposed between the electret and the probe. A capacitor connecting the electrodes is discharged and the shutter opened to induce a charge on the probe. This charge is drawn from the capacitor and the voltage thus generated across the capacitor is measured with an electrometer. Since electrode spacing is fixed, repeated measurement yields the same measure and the charges on different samples are directly comparable.