Device for the investigation of the physical properties of in a liquid or gaseous medium suspended particles

摘要

1367528 Particle analysis COULTER ELECTRONICS Ltd 22 Dec 1971 [28 Dec 1970] 59814/71 Heading G1N The Specification relates to deriving a particle signal 4, from Coulter type apparatus, which is independent of slow variations in the aperture impedance due to e.g. variations in the suspension liquid by making the aperture impedance equal to the geometric mean of the source impedance and the input impedance of the detector. This may be done by matching the input impedance of the amplifier to the effective aperture impedance for optimium signal transfer. With a D.C. energized aperture a differentiating amplifier may be used. With A.C. (radio frequency) a sharply resonant filter is arranged to reject a steady carrier-frequency and pass on only the signal modulated sideband. In particular examples:- (a) with D.C. energization in Fig. 1 (not shown) where the aperture is in shunt with the source, a D.C. blocking capacitor (13) is used, and when the aperture is in series with the source an inductance (23) is connected across the signal path. (b) with Radio-Frequency energization a series crystal-gate or series-resonant circuit connected across the signal is used Figs. 6 and 7 (not shown).