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:
Jun. 20, 1989
Filed:
Jun. 01, 1987
Lawrence C Maier, Middlebury, VT (US);
Simmonds Precision Products, Inc., Tarrytown, NY (US);
Abstract
Apparatus for the ratiometric measurement of a quantity of liquid in a tank includes first and second capacitors disposed in a tank and responsive to an AC excitation signal. The output signal from the first capacitor corresponds to the quantity of liquid in a tank, while the output signal of the second capacitor corresponds to an empty tank condition. First and second rectifiers are respectively coupled to the first and second capacitors. Preferably, the rectifiers are each a diode pair of opposite polarity diodes. The output signal from each rectifier is thus a current signal. A first current-to-voltage converter is coupled to both the first and second rectifiers and provides a first voltage signal corresponding to the first and second rectified signals. A second current-to-voltage converter is coupled to the second rectifier and provides a second voltage signal corresponding to the second rectified signal. A ratio device is coupled to the outputs of both voltage-to-converters and forms a ratio of the first and second voltage signals to provide an output signal indicative of the quantity of liquid in the tank. This output signal is insensitive to diode characteristics, variations in the excitation voltage and frequency, and produces a true zero output when the sensed quantity of liquid in a tank is zero.