AXIALE TRAJECTEN-SENSOR VOOR EEN ELEKTRONISCHE PARTIKELANALYSEERINRICHTING EN WERKWIJZE VOOR HET AFTASTEN VAN DOOR PARTIKELS OPGEWEKTE PULSEN

A sensor for use with apparatus operating in accordance with the principles of the Coulter electronic particle studying device for differentiating between signals from particles passing on axial or near axial trajectories through an aperture and particles passing off center. The particle pulse duration is measured at two or more fractions of the amplitude for each individual particle pulse. These pulse durations so measured are converted into voltages which represent the respective durations of the several fractional amplitudes and are compared with certain reference voltages. The reference voltage for one fractional amplitude is derived from a memory circuit which remembers the duration at that same fractional amplitude for the smallest of prior pulses processed by the sensor. Using this information, a reference voltage is established for that one fractional amplitude as the maximum permissible level below which the duration-representing voltage is acceptable and above which the duration-representing voltage is not acceptable. This same reference voltage derived from the memory circuit is used to establish maximum and minimum levels for the other fractional amplitude duration-representing voltages. In addition to the one duration-representing voltage falling below its reference level, the duration-representing voltages of all other fractional amplitudes must fall between the maximum and minimum reference voltages, respectively, which have been established for them in order to operate gating means to pass the particle pulse. All other pulses will be disregarded. On such account, pulses must have the proper shape and duration to be passed by the sensor.