Capacitive pressure transducer with improved electrode

• US 4,158,217 A
• Filed: 12/02/1976
• Issued: 06/12/1979
• Est. Priority Date: 12/02/1976
• Status: Expired due to Term

• Current Assignee: Kaylico Corporation
• Original Assignee: Kaylico Corporation
• Inventors: Bell, Robert L.
• Primary Examiner(s): Goldberg, E. A.
• Application Number:
  US05/746,853
• Time in Patent Office: 922 Days
• Field of Search: 361/283, 361/303, 361/304, 361/278, 361/289, 361/298, 361/299, 344/61 P, 73/398 C, 73/718
• US Class Current: 361/283.4
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass
• CPC Class Codes: G01L 9/0086 using variations in capacitance

Abstract

An electrode for use in capacitive pressure transducers of the type including either a single diaphragm electrode and a conductive reference plate separated by a gap or two diaphragm electrodes separated by a gap. The electrode comprises a conductive area having a plurality of nonconductive areas in the conductive area arranged and configured such that the capacitive fringe effects of the nonconductive areas substantially reduces the nonlinear component of the variation in the capacitance of the capacitive pressure transducer as a function of pressure.

Claims

1. A capacitive pressure transducer comprising:

a pair of electrically insulative members, at least one of said electrically insulative members comprising an elastic diaphragm, said members being disposed one adjacent to the other and defining a gap there between;

a conductive layer applied to the inside surface of said members forming first and second layers, said layers being opposite and adjacent to each other across said gap;

means for bonding said members together in a spaced relationship to form a gap whereby the gap varies with the pressure applied to the transducer, thereby varying the capacitance between conductive members, said pressure being applied to apply a force to at least one of said members, and deflect said member in the direction of the force;

one of said conductive layers having a central electrically conductive area, said central conductive area defining a plurality of non-conductive areas arranged within said central conductive area and configured to create a capacitive fringe effect with said other layer of said transducer to minimize the non-linear component of the variation in the capacitance and the impedance of said capacitive pressure transducer as a function of pressure, whereby the transducer will supply a signal that is substantially more linear as a result of said pressure being applied to said transducer.

2. A capacitive pressure transducer comprising:

a first essentially planar diaphragm member made from an electrically insulative and elastic material having a low hysteresis, said planar member having a thickness that enables said member to be deflected when pressure is applied thereto and having on at least one side thereof a thin conductive layer intimately and inseparably adhered thereto forming an electrode member;

a second essentially planar member formed from the same material as the first planar member, said second planar member having a thin conductive layer intimately and inseparably adhered thereto on at least one side thereof to form an electrode member, said first planar member and said second planar member being disposed one on the other and being arranged and configured such that when said first planar member is disposed on said second planar member there exists a gap between said first planar member and said second planar member and said electrode members thereon are in opposition to one another;

one of said electrode members comprising;

a central electrically conductive area; and

a plurality of electrically nonconductive areas defined by said central conductive area within said central conductive area, said non-conductive areas being arranged and configured to create a capacitive fringe effect to substantially minimize the non-linear component of variation in the capacitance of said pressure transducer as a function of pressure;

means for bonding the first planar member to the second planar member forming a capacitor which has a capacitance that varies with the pressure applied to the transducer as a result of deflection of said planar members with respect to one another, with said variation of capacitance having its non-linear component minimized by the configuration of at least one of the electrode members.

3. The capacitor according to claim 2 wherein said nonconductive areas form a plurality of a curved concentric areas with the center of said central conductive area.

4. The capacitor according to claim 2 wherein said nonconductive areas form a plurality of intersecting spaces having a star-like configuration.

5. The capacitor according to claim 2 wherein said diaphragm is an electrically nonconductive material and said electrodes are in the form of a film of metalization and said nonconductive areas are in the form of openings in said film.

6. A capacitive pressure transducer comprising:

a first essentially planar diaphragm member made from an electrically insulative and elastic material having a low hysteresis, said planar member having on at least one side thereof a thin conductive layer intimately and inseparably adhered thereto forming an electrode member;

a second essentially planar member formed from the same material as said first planar member, said second planar member having a thin conductive layer intimately and inseparably adhered thereto on at least one side thereof to form an electrode member, said first planar member and said second planar member being disposed one on the other and being arranged and configured such that when said first planar member is disposed on said second planar member there exists a gap between said first planar member and said second planar member and said electrode members thereon are in opposition to one another;

means for bonding the first planar member to said second planar member in a spaced relationship to form said gap thereby forming a capacitor which has a capacitance that varies with the pressure applied to the transducer as a result of the deflection of at least one of said planar members with respect to the other; and

at least one of said electrode members having a central electrically conductive area defining a plurality of openings in said central conductive area to effect a capacitive fringe effect between the edges of said openings and the other electrode member of said transducer to minimize the non-linear component of the variation in capacitance which non-linear component would otherwise occur upon the deflection of at least one of said planar members with respect to the other planar member.

7. The capacitor according to claim 6 wherein said plurality of openings are concentric with the center of said central area.

8. The capacitor according to claim 6 wherein said openings are straight nonconductive areas defining a star-like configuration.

9. A capacitive pressure transducer comprising:

a pair of members each carrying an electrode thereon, which electrodes are in an opposed relationship to one another, at least one of said members being subject to deflection to and from said other member upon the application of pressure thereto, said electrode bearing members being in spaced relationship so that the deflection of one member with respect to the other member results in a change in the spacing of one electrode with respect to the other electrode;

at least one of said electrodes comprising;

a central electrically conductive area; and

a plurality of electrically non-conductive areas provided in said central conductive area, said non-conductive areas being arranged and configured to create a capacitive fringe effect to substantially minimize the non-linear component of the variation of capacitance and impedance of said capacitive pressure transducer as a function of pressure.

10. The capacitor according to claim 9 wherein said nonconductive areas form a plurality of curved areas concentric with the center of said central conductive area.

11. The capacitor according to claim 9 wherein said plurality of nonconductive areas form a star-like configuration.

12. The capacitor according to claim 9 wherein said diaphragm is electrically nonconductive material and said electrodes are in the form of a film of metallization and said nonconductive area is in the form of openings in said film.

13. The capacitor according to claim 12 wherein said nonconductive material is alumina.