Abstract
A charge measuring method was developed to measure the charge distribution of nanometer-sized particles at low pressure. The measuring apparatus consists of a parallel electrode condenser and a backup filter. The ratios of positively charged particles, negatively charged particles, and uncharged particles to total particles are obtained from weights of the particles collected by the electrodes and the filter. The performance of this measuring device was found from the theoretical investigation to depend on two dimensionless parameters which express the relative intensity of Brownian diffusion and electrophoresis. The charging ratios of nanometer-sized SiO2 particles charged by bipolar ions at an atmospheric pressure agreed well with theoretical results for bipolar diffusion charging.
