Liquid gauging apparatus with a magnetoresistive sensor and remote sensor interrogration

• US 5,814,830 A
• Filed: 06/01/1995
• Issued: 09/29/1998
• Est. Priority Date: 10/18/1994
• Status: Expired due to Term

• Current Assignee: Simmonds Precision Products, Inc. (Rtx Corporation)
• Original Assignee: Simmonds Precision Products, Inc. (Rtx Corporation)
• Inventors: Crowne, David Henry
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US08/457,085
• Time in Patent Office: 1,216 Days
• Field of Search: 250/577, 250/551, 250/221, 250/904, 340/870.16, 340/870.28, 340/870.37, 340/870.72, 340/623, 73/61.41, 73/314, 73/305, 338/33
• US Class Current: 250/577
• CPC Class Codes: G01F 23/72 using magnetically actuated indicating means
• CPC Class Codes: G01F 23/80 Arrangements for signal processing

Abstract

A liquid gauging system for a liquid container, the system comprising sensor means for producing a first electromagnetic signal that corresponds to liquid quantity in the container, and remote interrogation means for receiving the first electromagnetic signal and producing a system output that corresponds to the liquid quantity; the sensor means being energized by a second electromagnetic signal transmitted by the remote interrogation means.

Claims

1. A sensor for detecting liquid level comprising an elongate body disposable in the liquid, a float adapted to slide along said body in relation to level of the liquid, said float comprising first magnetic means for actuating a second magnetic means inside said body for producing a sensor output related to the liquid level;

said second magnetic means comprises a magnetoresistive sensor means having a sensor resistance connected to two sensor terminals wherein said sensor resistance between said terminals varies in relation to position of said float; and

encoder means coupled to said terminals for detecting said sensor resistance and converting said detected sensor resistance into an output that is characterized by a series of pulses having a timing relationship between said pulses, with said timing relationship corresponding to the liquid level.

2. The sensor of claim 1 wherein said magnetoresistive means comprises a linear resistive element and contact means magnetically actuated by said first magnetic means for changing resistance of said element.

3. The apparatus of claim 1 wherein said series of pulses comprises at least three pulses including first and second reference pulses, and a liquid level pulse that occurs in time between said reference pulses.

4. The apparatus of claim 3 wherein said first reference pulse occurs at time T1, said second reference pulse occurs at time T3, and said liquid level pulse occurs at time T2, wherein liquid level is obtained by the ratio T1-T2!/ T2-T3!.

5. The apparatus of claim 4 comprising an electromagnetic transmitting device, wherein said pulses are used to activate said electromagnetic device for transmitting through free space electromagnetic energy in pulses having a timing relationship that corresponds to the timing relationships between said reference and liquid level pulses.

6. The apparatus of claim 1 wherein said encoder means comprises a voltage source connected to a reference resistor that produces a reference current in relation to said voltage source;

said voltage source also being connected to said sensor resistance to produce a sensor current;

said encoder means further comprising comparison means for comparing said reference current and said sensor current to a time variant signal to produce said pulses.

7. The apparatus of claim 6 wherein said voltage source is energized by electromagnetic energy transmitted through free space received at the sensor, the sensor comprising power supply means for converting said received electromagnetic energy into electrical energy for said voltage source.

8. The apparatus of claim 6 wherein said comparison means comprises means for converting said reference current into first and second reference voltages and for converting said sensor current into a sensor voltage;

said comparison means producing a first reference pulse based on said first reference voltage, a second reference pulse based on said second reference voltage, and a liquid level pulse based on said sensor voltage;

wherein said liquid level pulse occurs in time between said reference pulses.

9. The apparatus of claim 8 wherein said time variant signal is a ramped voltage signal, said comparison means further comprising a comparator having one input connected to said ramped voltage signal, and a second input selectively connected by a switching means to said first and second reference voltages and sensor voltage.