Method and apparatus for detecting liquid composition and actual liquid level

Patent 5051921 Issued on September 24, 1991. Estimated Expiration Date:

November 30, 2009. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.

Abstract Claims Description Full Text

Patent References

3768006

3774237

3846073

3876916

Apparatus for detecting the presence of water in a fuel tank
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Inventor: Pope

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Inventor

Paglione, Robert W.

Assignee

David Sarnoff Research Center, Inc.

Application

No. 443527 filed on 11/30/1989

US Classes:

702/52, Capacitive sensor73/1.73, Liquid level or volume measuring apparatus73/304C, Capacitative331/65, WITH DEVICE RESPONSIVE TO EXTERNAL PHYSICAL CONDITION340/618, Liquid340/620Electrode probe

Examiners

Primary: Lall, Parshotam S.
Assistant: Mattson, Brian M.

Attorney, Agent or Firm

Burke; W. J.

International Classes

G01F 023/26
G01R 027/00

Abstract

A liquid level and composition sensor includes a first interdigitated capacitor mounted substantially vertically in a tank, and a second interdigitated capacitor mounted substantially horizontally in and near the bottom of the tank. An electronic processor is responsive to the value of capacitance of the first capacitor for producing a first voltage signal proportional to the level of the liquid in the tank and is responsive to the value of capacitance of the second capacitor for producing a second voltage signal having a voltage level corresponding to the composition or dielectric constant of the liquid. The processor also multiplies the first and second voltage signals together to produce a liquid level voltage output signal having a constant slope for voltage amplitude versus liquid level, regardless of the composition of the liquid in the tank.