Abstract: A particle analyzing device in which a suspension of particles in a fluid medium is passed through an aperture in a strip of plastic material, and the change in the conductivity of the suspension across the aperture, each time a particle flows through the aperture, is detected so that the number and volume of particles for a given quantity of the suspension can be determined. The strip can be provided with a plurality of scanning apertures and be selectively moved across the flow path to bring a new aperture into an operative position in the flow path, such as when an aperture becomes clogged by debris.