Capacitive pressure sensor with moving or shape-changing dielectric

• US 6,122,972 A
• Filed: 03/04/1998
• Issued: 09/26/2000
• Est. Priority Date: 03/04/1998
• Status: Expired due to Fees

• Current Assignee: Veris Industries LLC (Schneider Electric SE)
• Original Assignee: Veris Industries LLC (Schneider Electric SE)
• Inventors: Crider, Jim
• Primary Examiner(s): FELBER, JOSEPH LEON
• Application Number:
  US09/034,976
• Time in Patent Office: 937 Days
• Field of Search: 73/706, 73/718, 73/724, 73/749, 361/283.4
• US Class Current: 73/724
• CPC Class Codes: G01L 13/04 using floats or liquids as sensing elements
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/0095 using variations in capacitance

Abstract

A pressure sensor system includes a first conductive surface electrically isolated from a second conductive surface. A dielectric material is interposed between the first conductive surface and the second conductive surface. The dielectric material is movable with respect to at least one of the first conductive surface and the second conductive surface in response to a change in pressure exerted on the pressure sensor. A measurement system is connected to at least one of the first conductive surface and the second conductive surface to measure the capacitance between the first conductive surface and the second conductive surface representative of pressure.

Claims

1. A pressure sensor comprising:

(a) a first conductive surface electrically isolated from a second conductive surface;

(b) a dielectric material interposed between said first conductive surface and said second conductive surface;

(c) said dielectric material being movable with respect to at least one of said first conductive surface and said second conductive surface in response to a change in pressure exerted on said pressure sensor;

(d) a measurement system connected to at least one of said first conductive surface and said second conductive surface to measure the capacitance between said first conductive surface and said second conductive surface representative of said pressure; and

wherein said first conductive surface and said second conductive surface are nonparallel with respect to each other, so that the distance between said first and second conductive surfaces at one location is different from the distance between said first and second conductive surfaces at another location.

2. A pressure sensor comprising:

(a) a first conductive surface electrically isolated from a second conductive surface;

(b) a dielectric material interposed between said first conductive surface and said second conductive surface;

(c) said dielectric material being movable with respect to at least one of said first conductive surface and said second conductive surface in response to a change in pressure exerted on said pressure sensor;

(d) a measurement system connected to at least one of said first conductive surface and said second conductive surface to measure the capacitance between said first conductive surface and said second conductive surface representative of said pressure; and

wherein said first conductive surface and said second conductive surface have dissimilar shapes.

3. The pressure sensor of claim 2 wherein said first conductive surface is substantially rectangular and said second conductive surface is substantially triangular.

4. A method of measuring pressure comprising the steps of:

(a) providing a first conductive surface electrically isolated from a second conductive surface;

(b) moving a dielectric material interposed between said first conductive surface and said second conductive surface with respect to at least one of said first conductive surface and said second conductive surface in response to a change in pressure;

(c) determining a pressure by measuring the capacitance between said first conductive surface and said second conductive surface; and

wherein said first conductive surface and said second conductive surface are nonparallel to each other, so that the distance between said first and second conductive surfaces at one location is different from the distance between said first and second conductive surfaces at another location.

5. A method of measuring pressure comprising the steps of:

(a) providing a first conductive surface electrically isolated from a second conductive surface;

(b) moving a dielectric material interposed between said first conductive surface and said second conductive surface with respect to at least one of said first conductive surface and said second conductive surface in response to a change in pressure;

(c) determining a pressure by measuring the capacitance between said first conductive surface and said second conductive surface; and

wherein said first conductive surface and said second conductive surface have dissimilar shapes.

6. The method of claim 5 wherein said first conductive surface is substantially rectangular and said second conductive surface is substantially triangular.

7. A method of measuring pressure comprising the steps of:

(a) providing a first conductive surface electrically isolated from a second conductive surface and defining a gap therebetween;

(b) moving said first conductive surface with respect to said second conductive surface, while said first and second conductive surfaces are in contact with a dielectric material therebetween, said dielectric material occupying less than all of said gap and having a density greater than air, in response to a change in pressure exerted on a pressure sensor; and

(c) determining a pressure by measuring the capacitance between said first conductive surface and said second conductive surface.

8. A pressure sensor comprising:

(a) a first conductive surface electrically isolated from a second conductive surface;

(b) a dielectric material interposed between said first conductive surface and said second conductive surface;

(c) said dielectric material being movable with respect to at least one of said first conductive surface and said second conductive surface in response to a change in pressure exerted on said pressure sensor;

(d) a measurement system connected to at least one of said first conductive surface and said second conductive surface to measure the capacitance between said first conductive surface and said second conductive surface representative of said pressure; and

(e) wherein at least one of said first conductive surface and said second conductive surface is housed withing a body comprised of a nonconductive material, said body defining a first channel in fluid communication with both at least one diaphragm attached to said body and at least one of said first conductive surface and second conductive surface.

9. The pressure sensor of claim 8 further comprising a pair of nonconducting surfaces interconnecting said first conductive surface and said second conductive surface, thereby defining a second channel between the combination of said first conductive surface, said second conductive surface, and said pair of nonconducting surfaces.

10. The pressure sensor of claim 9 wherein said second channel has a cross section that is generally rectangular in shape.

11. The pressure sensor of claim 8 wherein said dielectric material has a dielectric constant greater than 9.

12. The pressure sensor of claim 8 further comprising another diaphragm attached to said body, wherein said dielectric material is located within a fluid path interconnecting said diaphragms.

13. The pressure sensor of claim 8 wherein at least one of said first and second conductive surfaces is formed by coating a metal on a portion of said body.

14. A pressure sensor comprising:

(a) a first conductive surface electrically isolated from a second conductive surface;

(b) a dielectric material interposed between said first conductive surface and said second conductive surface;

(c) said dielectric material being movable with respect to at least one of said first conductive surface and said second conductive surface in response to a change in pressure exerted on said pressure sensor;

(d) a measurement system connected to at least one of said first conductive surface and said second conductive surface to measure the capacitance between said first conductive surface and said second conductive surface representative of pressure; and

(f) said first conductive surface and said second conductive surface opposing each other and defining a volume therebetween, said dielectric material occupying a space smaller than said volume.