The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 25, 1986
Filed:
Sep. 21, 1984
Robert C Collins, Troy, MI (US);
Berwind Corporation, Philadelphia, PA (US);
Abstract
A system for indicating level of material in a vessel as a function of material capacitance comprising a bridge circuit which includes a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An adjacent bridge arm includes a plurality of capacitors coupled to controlled electronic switches for selective connection into the bridge circuit. The bridge circuit is powered by an rf oscillator, and a differential amplifier is connected across the bridge circuit for detecting the balance condition of the bridge. An automatic calibration circuit includes a digital counter having outputs connected to the electronic switches. A comparator is responsive to the differential amplifier for enabling operation of the counter during a calibration mode of operation for selectively connecting the fixed capacitors into the bridge circuit until a preselected balance condition, corresponding to a preselected reference material level, is obtained. Thereafter, the differential amplifier is responsive to variation of probe capacitance from the reference level to indicate material level.