Measurement of micrometer particles by means of induced charges

The principles of measuring the change in electric flux density, of dD/dt, are discussed in the context of performing highly sensitive charge measurements. As application examples, results are presented for point sensors used to measure particle velocity in a circulating fluidized bed and for a particle counter that detects particles down to 2 mu m diameter due to their electric charge. An aerosol analyzer based on the same measurement principle is discussed. The analyzer gives qualitative results on particle sizes and particle densities in aerosols with particle diameters of 10 to 500 nm and concentrations of 10/sup 6/ to 10/sup 12/ particles/m/sup 3/. It is concluded that the dD/dt measurement technique is a useful supplement to the commonly used optical systems.<>