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Electrical sensing circuitry for particle analyzing device

  • US 3,944,917 A
  • Filed: 08/13/1973
  • Issued: 03/16/1976
  • Est. Priority Date: 08/13/1973
  • Status: Expired due to Term
First Claim
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1. Electrical sensing circuitry for a particleanalyzing device wherein liquid containing particles is caused to flow through a sensing aperture on either side of which is located a sensing electrode, said circuitry being independent of slow changes in aperture diameter and including constant voltage means coupled to said electrodes for establishing an electric excitation current through said aperture and means coupled to said electrodes for detecting signals generated by particles passing through said aperture, said means for establishing an electric excitation current through said aperture having a low output impedance at D.C.and said means coupled to said sensing electrodes for detecting signals generated by particles passing through said aperture having a low input impedance at the frequencies of the particle-generated signals, said circuitry including circuit means for coupling said signal-detecting means, said electrical excitation current establishing means, and the voltage potential across said aperture in such a manner that the D.C. component of the excitation current flowing through said aperture is made to vary inversely proportional to slow changes of the steady state resistance of the resistance across said sensing electrodes through said aperture with voltage across said sensing electrodes remaining constant.

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