Abstract: An improved electrical sensing zone apparatus and method for counting and measuring size of particles suspended in a diluted electrolytic solution. The apparatus includes an aperture that is optimized with the use of double or single tapered shapes that approximate a hyperboloid of one sheet. The flow rate is selectably controlled to maintain a sufficiently low Reynolds number to avoid boundary layer separation effects that cause noise and consequently low sensitivity. By measuring statistical moments within the aperture, an approximation of the distribution of particle sizes is achieved.

Abstract: Improvements to the electrical sensing zone instrument are described that allow the good accuracy of this type of instrument to be applied to the measurement of the size of particles of carbon black. The improvements include a concentrated aqueous electrolyte containing KI or NaI, a surfactant soluble in the electrolyte capable of dispersing particles of carbon black, and an anode electrode that is made of silver at the surface touching the electrolyte. The silver anode electrode prevents the degradation of the electrolyte by light and electrolysis.

Abstract: A debris detector for a particle counter, such as a blood cell counter, of the COULTER (R) type. When a particle, or transient debris, passes through the sensing orifice of the particle detector, a voltage pulse occurs; whereas, when debris lodges in or against the orifice of the particle detector, a d.c. voltage shift occurs. The voltage at the orifice is capacitively coupled to an amplifier and the output of the amplifier is integrated. The capacitor coupling the orifice voltage to the amplifier causes an undershoot voltage at the trailing edge of each particle or transient debris pulse, such that a zero average voltage is applied to and, hence, from the amplifier for each voltage pulse. The integrated voltage is applied to a voltage comparator to provide an output signal therefrom whenever the integrated voltage exceeds a reference voltage. The comparator output signal is provided to a delay circuit having a delay related to the time required for a particle to pass through the COULTER detector orifice.

Abstract: An amplifier circuit having an input circuit of resistance and capacitance which is a.c. coupled to a source of pulses, and a feedback circuit of resistance and capacitance. The RC time constants of the input and the feedback circuits are made to be approximately equal at the time of pulse input in order to insure an output pulse flat base line without undershoot or overshoot.

Abstract: A centrifugal feeder includes a cylindrical feeder disc having an upwardly inclined uniform surface which is designed to expel particles placed thereon in a predetermined fashion by centrifugal force. The upwardly inclined surface of the disc may be designed to have a first predetermined expulsion rate which is the initial speed at which the disc must be rotated to expel any of the particles from the surface thereof. The disc also may be designed to have a final expulsion rate at which all particles placed on the surface thereof are expelled. The disc is rotated at a controlled rate of speed and at a controlled rate of change of speed to expel the particles in the manner desired in a linear or non linear fashion. The feed or expulsion rate of the particles is determined by the design of the disc and the rotation speed of the disc and essentially is independent of the size and density of the particles and the viscosity of the surrounding fluid in which the disc is rotated.