GB1160026A - Improved Pulse Analyzing Apparatus and System - Google Patents

Abstract

1,160,026. Voltage measurement; electrophysical measurement. COULTER ELECTRONICS Ltd. Feb.23, 1967 [Feb. 23, 1966; Feb. 7, 1967], No. 8791/67. Headings G1N and G1U. [Also in Division H3] In apparatus for determining the pulse amplitude at the centre of the pulse, the pulse is integrated in such manner that the curve of the integrated pulse is equal to that of the input pulse at the time centre of the input pulse, a gate is arranged to be opened when the two curves reach equality at the time centre, said gate passing a signal, equal to the pulse amplitude at the time centre, for a fixed time period. Detecting particles in fluids. The invention is applicable to particle detection systems of the type described in Specification 722, 418, Fig. 1. (not shown) relates to the isopotential lines surrounding an aperture in a sapphire wafer separating two liquid-containing chambers. It is shown that the shape of the current pulse produced between the two liquids when a particle of given size passes through the aperture is a function of the path of the particle relative to the axis of the aperture; the peak value of the current pulse only coinciding with its time centre when the pulse travels along the axis. It is shown that the pulse magnitude at its time centre is constant for a given sized particle, irrespective of the path through the aperture, hence when pulses are manipulated by the system described below, a more accurate determination of particle size is obtained. Reference is made to the use of a long aperture followed by a low pass filter or to the rounding of the contours of the aperture so as to provide more uniform current density. Such methods are, however, stated to be less advantageous than the system described below. Determination of pulse amplitude at the time centre. As shown in Fig. 2, pulses 52, Fig. 3, from 40 (derived from the current through an aperture in a wafer separating two conductive liquids) are passed via a gate 68 to an integrator 74 which provides a curve 76, Fig. 3, adjusted to become equal to that of the curve 52 at a time approximately equal to its time centre. A monostable multi-vibrator 114 is triggered by circuits 82,104,108 when the instantaneous values of the integrated pulse 76 and input pulse 52 are equal i.e. at substantially the time centre of the input pulse 52. The output of 114 opens a gate 120 which passes the centre value 124 of the pulse 52 to classification circuits 134 for a short period. Noise is inhibited by a threshold circuit 56, feeding a leading edge detector 140 and bi-stable circuit 66. This arrangement ensures that only pulses the amplitude of which exceeds the threshold of 56 are passed by the electronic switch 68. Circuits 56,66,74 are reset by the trailing edge of the pulse from 114. In Figs. 5, 6 (not shown) the mono-stable multivibrator 114 provides a longer duration pulse which is used to gate the output of the integrator which, in this case, is arranged to remain constant at the value reached at the time centre of the input pulse.