Abstract: Apparatus for sensing and characterizing particles suspended in a liquid medium includes a particle-sensing structure having a continuous wall defining a hydrodynamically smooth conduit through which the liquid suspension of particles is caused to pass simultaneously with an electrical current. Particles passing through the conduit are sensed and characterized by monitoring changes in the electrical current through the conduit. According to the invention, the continuous, conduit-defining wall is made entirely of a material having an electrical resistivity less than or equal to that of the liquid medium. Thus, the apparatus of the invention is similar to the conventional Coulter aperture (conduit) except that the aperture is formed from an electrically conductive material instead of a dielectric material.

Abstract: A Coulter apparatus comprises a volumeter assembly containing a conduit through which a particle suspension is caused to pass simultaneously with an electrical current. In preferred embodiments the volumeter assembly comprises at least one traditional Coulter conduit wafer, i.e., a dielectric wafer containing a central circular conduit, and at least two electrically conductive collars. The conductive collars approximate the conduit diameter in thickness, are uninsulated, and are attached to opposite sides of the conduit wafer, the openings being congruent with the Coulter conduit. The Coulter conduit in the dielectric wafer and the openings in the conductive collars collectively form a hydrodynamically smooth conduit, in which the electric and hydrodynamic fields of the Coulter conduit are amended. The electric field is shaped to confine the particle-sensitive zone of the novel volumeter conduit within the conduit's physical boundaries, thereby decreasing the zone's coincidence volume.

Abstract: A solenoid operated pinch valve including a housing and a hollow molded body coupled to said housing by a snap-on connection, a solenoid coil assembly seated within the housing, a plunger accommodated within said solenoid coil assembly for axial movement relative thereto controlled by energization of said solenoid coil assembly and between a pair of positions, said plunger having an end portion extending from the housing into said body and an opposite end portion received within said solenoid coil assembly, the body having a circumferential flange capable of being seated on one end of the housing and a pair of inflexible arms extending from the body in a coaxial direction relative thereto, said arms defining a passage for receiving a conduit across the path of movement of said plunger, a first orthogonal slot and a pair of resilient arms extending to the opposite end of the housing and engagable therewith in a snap-on coupling. One end of the plunger carries a second orthogonal slot.

Abstract: Particle produced pulses are evaluated on an individual basis for shape symmetry, with significantly asymmetric pulses, becoming subject to editing, i.e. exclusion. Pulse symmetry is determined by measuring the areas under the pulse before and after the first pulse amplitude peak and then by comparing those pulse areas with respect to pre-established limits which are not based upon any of the pulses then being evaluated.