Digitally controlled variable impedance for current normalization in an electrolyte type particle sensing zone
AssigneeParticle Data, Inc.
InventorDennis Russell, Jr.
Life of this patent
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Abstract
A digitally controlled variable impedance, preferably for use in a current normalizer for particle analysis apparatus, includes a variable resistance connected to a counting register by a plurality of opto-isolaters in the form of light emitting diode-light responsive transistor combinations. The register is reset (or preset) to a predetermined count and operates to change the impedance value in response to receipt of each pulse of a pulse train. A circuit is provided to terminate counting in response to an interpulse interval of greater than a predetermined interval to indicate a null condition between pulse amplitude, the pulses traversing the impedance, and a reference amplitude.
Claims6
A digitally controlled variable impedance comprising:
- a pulse generator for generating a first train of electrical pulses of constant amplitude;
- a variable impedance;
- means for applying the pulse train to said variable impedance to cause generation of a second pulse train corresponding to the first pulse train, variation of the value of said impedance causing a corresponding variance in the amplitude of the pulses of the second pulse train;
- means for setting a reference amplitude value at a detection point;
- digital means operable in response to said first pulse train to vary said impedance;
- and
- detecting means for detecting matching of the amplitude of said second pulse train with reference amplitude value and causing said digital means to stop varying said variable impedance.
Dependencies are inferred from the claim text.