Abstract: A transducer for measuring particles suspended in a fluid is disclosed. The transducer includes an elongated tubular member having a particle-free fluid conducting channel and an aperture for permitting the flow of a particle containing fluid into the fluid conducting channel. The size of the particles is measured by measuring the impedance variation of the particle containing fluid as it passes through the aperture. Spurious variations of the impedance caused by reentry of the particles into the region about the aperture is prevented by spacing the wall of the channel opposite the aperture so that the particle containing fluid impinges thereon after passing through the aperture and so that the particle-free fluid transports the particles away from the aperture before the particles reenter the region about the aperture.

Abstract: A particle analyzing apparatus having an aperture retaining member positioned in a housing for obtaining signals from particles which pass through a scanning aperture. The aperture retaining member includes an elongate director tube into which the particles to be sensed are introduced for movement to and passage directly through the aperture. An aperture holder with the aperture provided therein is positioned at the terminus of the director tube but spaced a small distance therefrom to permit entry of ensheathing clean liquid within the space and passage of the ensheathing liquid through the aperture simultaneously with passage of the particles. The downstream side of the aperture is in liquid communication through a fluid circulating system with the upstream side thereof; a pump is interposed in the path of liquid communication between the upstream and downstream sides of the aperture to enable continuous recirculation of the liquid throughout the system.

Abstract: An aperture module for obtaining signals from microscopic particles suspended in a fluid which passes through a scanning aperture. A module housing including an aperture holder is mounted on a vessel or bath containing a body of the particulate liquid suspension to be tested. The aperture holder with aperture formed therein extends into the vessel to permit passage of the suspension through the aperture to an outlet chamber or passageway immediately behind the aperture. An inlet chamber or passageway in the module is connected to a source of clean electrolyte and in fluid communication with the outlet passageway. The outlet passageway is connected to a waste collecting container. A vacuum is applied to the collecting container to cause the clean electrolyte to be drawn through the inlet passageway and wash behind the aperture simultaneously with passage of the suspension through the aperture.

Abstract: A pneumatically operated liquid transfer valve structure formed of a pair of stationary elements sandwiching a slidably movable element which includes a two pair of spaced parallel arranged through passageways of precise known volume oriented normal to the direction of travel of the slidable element, said passageways adapted to communicate alternately between aligned ones of the two pair of similar passageways formed in each of the stationary elements and arranged axially aligned. The slidably movable element is propelled to its reciprocal positions by fluid pumps each of which includes a cylinder having a flexible diaphragm and a reciprocable plunger mounted on a piston. Each pump is arranged on opposite ends of the valve elements. The free ends of the plungers are arranged selectively to engage one or the other ends of the slidable element at the limits of its path of travel.

Abstract: A pneumatically operated liquid transfer valve assembly capable of segmenting and transferring plural different volumes of liquid from like numbered liquid flow paths established through the valve and depositing said segmented volumes into like numbered adjacent liquid flow paths under the influence of pressurized fluid. At least two pairs of liquid flow paths are established and a linearly movable valve element carrying at least two pairs of segmenting bores is arranged selectively to intercept said pairs of liquid flow paths. One of each segmenting bore pairs intercepting one of each pair of liquid flow paths at one condition of the valve and the valve element being translated linearly to place said one of each segmenting bore pair in communication with the other of each liquid flow path pair with the other of each segmenting bore pair intercepting said one of each liquid flow path pair; the members of each segmenting bore pair being identical in volume but each bore pair being different in volume.

Abstract: A particle analyzing system of the type having an aperture retaining member for obtaining signals from microscopic particles suspended in a fluid which passes through a scanning aperture. The aperture opens on one side thereof to the fluid suspension and on the opposite side to a passageway in the aperture retaining member; the passageway is connected at an entrance end thereof to a source of clean electrolyte and at an exit end thereof to a waste collecting container or isolator and a vacuum source. A vacuum from the source is applied to the collecting container to cause the clean electrolyte to be drawn through the passageway and wash or sweep behind the aperture simultaneously with passage of the suspension through the aperture.