<p>A fluid containing disbursed particles is pumped through an aperture which has a pair of electrodes mounted on each side of said aperture. The pair of electrodes is excited by an rf signal which is modulated by the particles passing through said aperture. The rf signal is then detected, filtered and amplified to provide pulses corresponding to the particles passing through the aperture. Means for charging a capacitor at a known rate during a portion of each pulse that exceeds a predetermined threshold level to develop a voltage on the capacitor corresponding to the number of particles per unit volume of the fluid medium, said voltage being independent of flow rate and the volume of fluid passed through the aperture. An alarm is provided to warn of a possible clogged aperture and a pulse width limiter is provided to prevent erroneous charging of the capacitor if a bubble passes through the aperture.</p>
