Digitally controlled variable impedance for current normalization in an electrolyte type particle sensing zone
US3947701A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 13, 1975 |
| Grant date | Mar 30, 1976 |
| Priority date | — |
| Expiry date | Jan 13, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M1/74
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.