Measurements of charge distributions: comparison of the PWP and the PEA techniques

Measurements of space charges in polymer materials are now possible with different techniques. This paper deals with a comparison of the pressure wave propagation (PWP) method and the pulsed electro acoustic (PEA) method. Two degassed PE samples of about 2 mm thickness contacted with semiconducting electrodes were used. The samples were polarized at 40 kV at 50/spl deg/C for 3 hours and short circuited for 1 hour. PWP and PEA data were measured for each sample during the polarization and short circuit phases. After short circuiting the samples were changed between the two systems. Both methods show very similar results with respect to surface and space charge distribution. However, there are differences in excitation of pressure waves and propagation which give minor differences between the PWP and the PEA method.