System generating a pressure profile across a pressure sensitive membrane

• US 5,983,727 A
• Filed: 08/19/1997
• Issued: 11/16/1999
• Est. Priority Date: 08/19/1997
• Status: Expired due to Term

• Current Assignee: Pressure Profile Systems Inc. (PPS U.K. Limited)
• Original Assignee: Pressure Profile Systems Inc. (PPS U.K. Limited)
• Inventors: Son, Jae S., Howe, Robert D., Wellman, Parris S.
• Primary Examiner(s): FELBER, JOSEPH LEON
• Application Number:
  US08/914,730
• Time in Patent Office: 819 Days
• Field of Search: 73/723, 73/724, 73/726, 73/727, 73/705, 73/701, 338/4, 338/42, 361/283.4, 250/231.19, 250/227.14
• US Class Current: 73/724
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

An improved fluid pressure sensor/sensor array is shown to provide high resolution, sensitivity which can be easily controlled based on anticipated or detected pressure range, and reliable pressure measurements with easy installation and low fabrication cost. A fluid pressure sensor is provided having a substantially incompressible mounting structure with a cavity formed therein. An elastic membrane is attached to said mounting structure and across said cavity, separating the cavity from the fluid to be measured. At least one non-contact transducer is attached to the mounting structure in the cavity to detect deflection at a selected plurality of regions on the membrane. The sensitivity and pressure range of the sensor can be chosen by preselecting the elasticity of the membrane, stretching the membrane across the cavity under a preselected tension, maintaining a predetermined reference pressure in the cavity, and/or actively controlling the membrane tension. For a pressure sensor array, there are at least two fluid pressure sensors, where at least one sensor is of the type described herein. A sensor array can also be formed by multiple cavities within a single mounting structure.

Claims

1. A sensor apparatus, to detect the pressure of a fluid, comprising:

(a) a substantially incompressible mounting structure having a cavity formed therein;

(b) an elastic membrane, attached to said mounting structure and across said cavity, so as to separate said cavity from said fluid; and

(c) at least one transducer mounted in said cavity, detecting deflection of said membrane at a selected plurality of regions thereon, facilitating the generating of a pressure profile across the membrane.

2. The sensor apparatus of claim 1, wherein there are a plurality of said transducers, each detecting deflection of at least one of said regions on said membrane.

3. The sensor apparatus of claim 2, wherein each of said transducers provides a substantially independent pressure measurement.

4. The sensor apparatus of claim 3, wherein said transducers are spaced sufficiently to minimize interaction therebetween.

5. The sensor apparatus of claim 1, wherein said membrane is constructed to deflect in directions both into and out of said cavity.

6. The sensor apparatus of claim 1, wherein said cavity formed in said mounting structure has a side wall, and wherein said transducers are arranged such that the spacing from a said cavity side wall to each region at which deflection is detected on said membrane is substantially uniform.

7. The sensor apparatus of claim 1, further including a mechanism for shielding the transducers.

8. The sensor apparatus of claim 7, further including a shield attached to an external side of said membrane.

9. The sensor apparatus of claim 7, further including a shield attached to an external side of the of said mounting structure.

10. The sensor apparatus of claim 1, wherein said mounting structure is formed from a material that is both flexible and substantially incompressible.

11. The sensor apparatus of claim 10, wherein said cavity is constructed to have a depth sufficient to allow deflection of said membrane into said cavity when the mounting structure is flexed.

12. The sensor apparatus of claim 1, wherein said mounting structure is comprised of a substantially incompressible substrate and a substantially incompressible spacer, the spacer being mounted on the substrate and having sides extending from the substrate which define said cavity.

13. The sensor apparatus of claim 12, wherein said transducers are mounted on the substrate.

14. The sensor apparatus of claim 12, wherein said transducers are mounted to the spacer.

15. The sensor apparatus of claim 12, wherein said membrane is attached to the substrate with an adhesive, and wherein the spacer is comprised of substantially incompressible beads embedded in the adhesive.

16. The sensor apparatus of claim 1, wherein said membrane is attached to the mounting structure with an adhesive having substantially incompressible beads embedded in the adhesive.

17. The sensor apparatus of claim 1, wherein said membrane is formed from a material of a preselected elasticity.

18. The sensor apparatus of claim 1, wherein said membrane is stretched across said cavity under a preselected tension.

19. The sensor apparatus of claim 1, wherein said cavity is constructed to maintain a predetermined reference pressure.

20. The sensor apparatus of claim 19, wherein said cavity includes a vent opening to a reference pressure.

21. The sensor apparatus of claim 20, further including a mechanism for controlling deflection of said membrane.

22. The sensor apparatus of claim 21, wherein the mechanism includes a mechanism for controlling the reference pressure.

23. The sensor apparatus of claim 21, wherein the mechanism controls deflection by adjusting the tension of said membrane.

24. The sensor apparatus of claim 1, wherein at least one of said transducers is a capacitor.

25. The sensor apparatus of claim 24, wherein said mounting structure includes a printed wiring board with connection traces and the at least one capacitor includes a sensing plate.

26. The sensor apparatus of claim 24, wherein said cavity is filled with a fluid to provide a predetermined dielectric constant.

27. The sensor apparatus of claim 1, wherein said transducers include at least one radiation emitter and at least one radiation receiver.

28. The sensor apparatus of claim 27, wherein the radiation emitter is a light source and the radiation receiver is an optical sensor.

29. The sensor apparatus of claim 27, wherein the radiation emitter is an ultrasonic pulse emitter and the radiation receiver is an ultrasonic pulse sensor.

30. A large area sensor system, to detect the pressure of a fluid, comprising at least two fluid pressure sensor apparatus, wherein at least one of the sensor apparatus is comprised of:

(a) a substantially incompressible mounting structure having a cavity formed therein;

(b) an elastic membrane, attached to said mounting structure and across said cavity, so as to separate said cavity from said fluid; and

(c) at least one transducer mounted in said cavity, for detecting deflection of said membrane at a selected plurality of regions thereon, facilitating the generating of a pressure profile across the membrane.

31. A large area sensor system, to detect the pressure of a fluid, comprised of:

(a) a substantially incompressible mounting structure having a plurality of cavities formed therein;

(b) an elastic membrane, attached to said mounting structure and across said cavities, so as to separate said cavities from said fluid; and

(c) at least one transducer mounted in each cavity, for detecting deflection at a selected plurality of regions of the membrane for each cavity, facilitating the generating of a pressure profile across the membrane.

32. The sensor system of claim 31, wherein at least two of the cavities are interconnected with a vent opening.

33. A fluid pressure sensor apparatus comprising:

at least one cavity;

a component extending over said at least one cavity which undergoes local displacement in response to corresponding local pressure differentials;

a plurality of displacement detectors in each said cavity, each of which converts a said local displacement to a signal; and

a reference pressure applied on one side of said component;

fluid pressure to be sensed being applied to the opposite side of the component.

34. The sensor apparatus of claim 33, wherein said displacement component displaces both toward and away from said applied reference pressure.

35. The sensor apparatus of claim 33, wherein each of said detectors provides a substantially independent measurement.

36. The sensor apparatus of claim 33, further including a means responsive to said detectors for controlling sensitivity of said sensor.

37. The sensor apparatus of claim 36, wherein the means for controlling sensitivity includes a mechanism for dynamically varying said reference pressure.

38. The sensor apparatus of claim 36, wherein said displacement component has a selected elasticity which is determined by said means for controlling sensitivity.

39. The sensor apparatus of claim 36, wherein the means for controlling sensitivity includes a means for dynamically controlling the tension of said displacement component.

40. The sensor apparatus of claim 33, wherein at least one of said detectors includes at least one means for emitting and at least one means for detecting a radiation signal.

41. The sensor apparatus of claim 33, wherein at least one of said detectors is a capacitor.

42. A sensor apparatus, to detect the pressure of a fluid, comprising:

(a) a substantially incompressible substrate;

(b) a substantially incompressible spacer mounted on said substrate and having sides extending from said substrate which define a cavity;

(c) an elastic, non-reactive membrane stretched across said cavity at a preselected tension, formed from a material of a preselected elasticity, attached to said spacer and arranged to separate said fluid from a predetermined reference pressure maintained in said cavity; and

(d) a plurality of transducers mounted on said substrate in said cavity to measure displacement at selected regions of said membrane, each transducer providing a substantially independent pressure measurement.

43. A method for detecting the pressure of a fluid comprising the steps of:

(a) maintaining a reference pressure on one side of an elastic membrane extending over at least one cavity;

(b) exposing another side of said membrane to a fluid pressure to be detected; and

(c) utilizing at least one transducer for each said cavity to measure the local displacement of the membrane over said cavity resulting from the pressure differential thereacross at a selected plurality of membrane regions, facilitating the generating of a pressure profile across the membrane.

44. The method for detecting of claim 43, further including the step of controlling deflection of the membrane in response to input from the transducer measurements.

45. A method for fabricating a pressure sensor comprising the steps of:

(a) providing a substantially incompressible mounting structure having a cavity formed therein;

(b) mounting a plurality of displacement transducers in said cavity; and

(c) attaching a membrane across said cavity;

said transducers being mounted to detect deflection at separate regions of said membrane, facilitating the generation of a pressure profile across the membrane.

46. The method of claim 45, further comprising the step of attaching a shield to the external side of said membrane.

47. The method of claim 45, further comprising the step of attaching a shield to the external side of said mounting structure.

48. The method of claim 45, wherein step (c) includes stretching said membrane to a preselected tension.

49. The method of claim 45, including a step (d) of creating a reference pressure in said cavity.

50. The method of claim 49, wherein step (d) includes forming a vent opening to said cavity.

51. The method of claim 45, wherein step (b) is performed by coating said mounting structure and said membrane with a conductive metal and etching sense pads and drive traces into the conductive metal.

52. The method of claim 45, wherein step (c) includes utilizing an adhesive having substantially incompressible beads mixed therein to attach said membrane to said mounting structure.

53. The method of claim 45, wherein step (a) includes the step of mounting a spacer on said mounting structure having sides extending from said mounting structure and forming a cavity therein.

54. The method of claim 53, wherein the step of mounting the spacer is performed by forming a spacer layer, removing a cutout from the spacer layer, and attaching the spacer layer to said substrate.