Simple apparatus for measurement of size and charge of particle in AC electric field

We developed a new simple apparatus for measuring both the size and the charge of fine particles from the amplitude and the phase shift of the particle oscillation in AC electric field. This apparatus composed of a digital camera, parallel plate electrodes, a high voltage AC source, an illuminating lamp and a flush lamp. The amplitude and the phase shift of each particle were measured from the image obtained by a digital camera. Measurements for multiple particles are carried out at the same time using this apparatus. The performance of the apparatus was confirmed by using glass beads of 30 /spl mu/m diameter and toner particles of 10 /spl mu/m diameter. Both the size and the charge can be measured within a few percent error.