Solid state fluid level sensor

• US 7,373,817 B2
• Filed: 07/09/2004
• Issued: 05/20/2008
• Est. Priority Date: 07/09/2004
• Status: Active Grant

• Current Assignee: Touchsensor Technologies LLC (Methode Electronics Incorporated)
• Original Assignee: Touchsensor Technologies LLC (Methode Electronics Incorporated)
• Inventors: Burdi, Roger D., Reniger, Bruce L.
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): Shah; Samir M.
• Application Number:
  US10/886,558
• Publication Number:
  US 20060005622A1
• Time in Patent Office: 1,411 Days
• Field of Search: 733/04.R, 733/04.C, 732/90.R, 732/90.V
• US Class Current: 73/290.00R
• CPC Class Codes: F04B 17/03 driven by electric motors
• CPC Class Codes: F04B 49/02 Stopping, starting, unloading or idling control
• CPC Class Codes: F04D 15/0218 the condition being a liquid level or a lack of liquid supply
• CPC Class Codes: G01F 23/261 for discrete levels
• CPC Class Codes: G01F 23/265 for discrete levels
• CPC Class Codes: G01F 23/266 measuring circuits therefor
• CPC Class Codes: G01F 23/268 mounting arrangements of probes
• CPC Class Codes: H05K 1/0268 for electrical inspection or testing
• CPC Class Codes: H05K 1/16 incorporating printed electric components, e.g. printed resistor, capacitor, inductor
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.

Abstract

A sensor system for sensing liquid level in a bilge, for use in automatic bilge pump actuation. First and second field effect sensors are potted or sealed within a container or the bilge wall and are aligned in a vertical array and each comprise a substantially planar pattern of “electrodes” or conductive traces disposed on a printed circuit board (PCB) along with integrated circuits used to create a loop or arc-shaped electric field. As bilge liquid rises to the proximity or level of the field effect sensors, a change in the arc-shaped electric field is sensed and, in response, a bilge pump is automatically actuated to pump liquid out of the bilge. Optionally, the pump control can be programmed by use of a microprocessor to permit control of on-off timing and prevent undesirable effects of “sloshing.”

Claims

1. A fluid level sensor apparatus for detecting a moving fluid level and capable of activating a controlled device, said fluid level sensor apparatus comprising:

a fluid-proof barrier having first and second opposite surfaces, wherein said first barrier surface is exposed to the fluid;

a fluid-proof housing enclosing a cavity proximate said fluid-proof barrier, said fluid-proof housing being adapted for submersion in said fluid whose level is to be detected;

a dielectric substrate sealed within said cavity;

at least one sensor disposed on said dielectric substrate, each said at least one sensor comprising;

a first thin, conductive sensing electrode in a closed, continuous geometric form having an area which affords substantial coverage by fluid contact with said barrier;

a second thin, conductive electrode in a spaced, coplanar and substantially surrounding relationship to said first sensing electrode; and

an active electrical component proximate said first and second sensing electrodes and electrically coupled to said first and second sensing electrodes, such that fluid contact with said barrier activates the controlled device.

2. The fluid level sensor apparatus of claim 1, wherein said substrate is overmolded within said housing cavity.

3. The fluid level sensor apparatus of claim 2 wherein an electric field is generated about said first and second sensing electrodes, said electric field having an arc-shaped path originating at said second sensing electrode and terminating at said first sensing electrode.

4. The fluid level sensor apparatus of claim 3, wherein said fluid level sensor generates a detection signal indicating the status of said fluid level sensor.

5. The fluid level sensor apparatus of claim 4, wherein the level of said detection signal is altered when said fluid level contacts said first surface of said barrier and approaches said substrate.

6. The fluid level sensor apparatus of claim 1 wherein said substrate is glass.

7. The fluid level sensor apparatus of claim 1 wherein said substrate is plastic.

8. The fluid level sensor apparatus of claim 1 wherein said substrate is made from a fiberglass reinforced epoxy resin.

9. The fluid level sensor apparatus of claim 1 wherein a channel is located between said first and second sensing electrodes, said channel having a generally uniform width.

10. The fluid level sensor apparatus of claim 1 further comprising at least one additional sensor disposed on said first surface of said substrate.

11. The fluid level sensor apparatus of claim 1 wherein said sensors are arranged in a vertical array.

12. The fluid level sensor apparatus of claim 1, wherein the controlled device is a pump.

13. The fluid level sensor apparatus of claim 1, wherein the controlled device is a bilge pump.

14. A low impedance fluid level sensor apparatus for detecting contact by a fluid and capable of activating a controlled device, said fluid level sensor apparatus comprising:

a dielectric carrier;

at least one sensor disposed on said dielectric carrier, each said at least one sensor comprising;

a first thin, conductive sensing electrode in a closed, continuous geometric form having an area which affords substantial coverage by a region of fluid contact;

a second thin, conductive sensing electrode in a spaced and substantially surrounding relationship to said first sensing electrode; and

a low impedance, active electrical component immediately adjacent said first and second electrodes and electrically coupled to said first and second sensing electrodes; and

a dielectric substrate having first and second opposite surfaces, said dielectric carrier disposed on said first surface of said dielectric substrate, such that fluid contact of said substrate activates the controlled device.

15. The apparatus of claim 14 wherein said first surface of said substrate is a non-fluid touching surface and said second surface of said substrate is a fluid touching surface.

16. A low impedance fluid proximity sensor apparatus for detecting fluid contact and capable of activating a controlled device, said fluid proximity sensor apparatus comprising:

a dielectric substrate having first and second opposite surfaces; and

at least one sensor disposed on said dielectric substrate, each said at least one sensor comprising;

a first thin, conductive sensing electrode in a closed, continuous geometric form having an area which affords substantial coverage by an area of fluid contact;

a second thin, conductive sensing electrode in a spaced, coplanar and substantially surrounding relationship to said first sensing electrode; and

a low impedance active device immediately adjacent said first and second sensing electrodes and electrically coupled to said first and second sensing electrodes, such that fluid contact with said dielectric substrate activates the controlled device.

17. The fluid proximity sensor apparatus of claim 16 wherein said active device is an ASIC configured to energize said electrodes with an oscillator signal.

18. The fluid proximity sensor apparatus of claim 17 further including at least one gain tuning resistor disposed on said substrate and electrically coupled between said ASIC and one of first and second electrodes.

19. The fluid proximity sensor apparatus of claim 18 further comprising at least one additional sensor disposed on said substrate.

20. The fluid proximity sensor apparatus of claim 18 wherein said fluid proximity sensor ASIC generates a detection signal in response to a rising fluid level.

21. A fluid proximity sensor for detecting a moving fluid and capable of generating a fluid presence detected signal or activating a controlled device, said fluid proximity sensor apparatus comprising:

a fluid-proof dielectric substrate of substantially uniform thickness having first and second opposite surfaces;

at least one sensor disposed on said first surface of said substrate, each said at least one sensor comprising;

a first thin, conductive sensing electrode in a closed, continuous geometric form having an area which affords substantial coverage by fluid contact with said substrate second surface;

a second thin, conductive sensing electrode in a spaced, coplanar and substantially surrounding relationship to said first sensing electrode; and

a low impedance, active electrical component immediately adjacent said first and second sensing electrodes and electrically coupled to said first and second sensing electrodes, such that fluid contact with said substrate second surface activates the controlled device.

22. The fluid proximity sensor of claim 21, wherein said first thin, conductive sensing electrode comprises a balanced pad electrode having an area that is substantially equal in area with the area of said second conductive sensing electrode.

23. The fluid proximity sensor of claim 22, wherein said balanced pad electrode comprises a substantially planar electrode having a plurality of conductive traces connected at an end to other conductive traces and separated by segments of non-conductive dielectric material.

24. The fluid proximity sensor of claim 23, wherein said balanced pad electrode has a substantially rectangular conductive perimeter.

25. The fluid proximity sensor of claim 23, further comprising a substantially planar conductive ground ring disposed on said substrate and encircling said second sensing electrode.

26. A fluid level sensor apparatus for detecting a moving fluid level and capable of activating a controlled device, comprising:

a fluid-proof housing enclosing a cavity;

a dielectric substrate having first and second opposite surfaces, said dielectric substrate sealed within said cavity;

at least one sensor disposed on said dielectric substrate, each said at least one sensor including,

a first thin, conductive sensing electrode in a closed, continuous geometric form having an area which affords substantial coverage by fluid contact with said housing;

a second thin, conductive electrode in a spaced, coplanar and substantially surrounding relationship to said first sensing electrode; and

an active electrical component proximate said first and second sensing electrodes and electrically coupled to said first and second sensing electrodes, such that fluid contact with said housing activates the controlled device.

27. The fluid level sensor apparatus of claim 26, wherein the controlled device is a pump.

28. The fluid level sensor apparatus of claim 26, wherein the controlled device is a bilge pump.

29. The fluid level sensor apparatus of claim 26, wherein said substrate is overmolded within said cavity.

30. The fluid level sensor apparatus of claim 26, wherein an electric field is generated about said first and second electrodes, said electric field having an arc-shaped path originating at said second sensing electrode and terminating at said first sensing electrode.

31. The fluid level sensor apparatus of claim 26, wherein said substrate is glass, plastic, or made from a fiberglass reinforced epoxy resin.

32. The fluid level sensor apparatus of claim 26, further comprising at least one additional sensor disposed on said first surface of said substrate.

33. The fluid level sensor apparatus of claim 26, wherein said sensors are arranged in a vertical array.

34. The fluid level sensor apparatus of claim 26, further comprising at least two electrical conductors for coupling said at least one sensor and said controlled device to a power supply.

35. The fluid level sensor apparatus of claim 26, further comprising a switching device coupled to said at least two electrical conductors for controlling the supply of power to said controlled device, said at least one sensor being connected to said switching device for turning said controlled device on and off in response to changes in the detected fluid level adjacent the outer surface of said cavity.