Capacitive pressure transducer

• US 4,287,553 A
• Filed: 06/06/1980
• Issued: 09/01/1981
• Est. Priority Date: 06/06/1980
• Status: Expired due to Term

• Current Assignee: The Bendix Corporation (Honeywell International Inc.)
• Original Assignee: The Bendix Corporation (Honeywell International Inc.)
• Inventors: Braunlich, Peter F.
• Primary Examiner(s): Goldberg, E. A.
• Application Number:
  US06/156,970
• Time in Patent Office: 452 Days
• Field of Search: 361/283, 73/718, 73/724, 65/43, 65/59 A
• US Class Current: 361/283.4
• CPC Class Codes: G01D 5/2417 by varying separation
• 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
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence

Abstract

A capacitive pressure transducer having a first flexible electrically insulative diaphragm disposed apart from a second electrically insulative member, including a second flexible diaphragm, and where the diaphragm and member include metalized portions thereon forming the plates of a pressure sensing capacitor.

The transducer further includes a pair of electrically insulative sealing rings disposed concentrically about one another which function to space said diaphragm and member apart and which form a hermetically sealed cavity therebetween, to establish the pressure sensitive region of the diaphragm and to reduce the tensile forces in the inner most sealing ring.

Claims

1. A capacitive pressure transducer comprising:

a first diaphragm having a pressure responsive region thereon and deflectable in response to the local pressure;

first means spaced from said first diaphragm defining a gap therebetween;

pressure responsive means applied to the said pressure responsive region of said first diaphragm for transducing said pressure to be measured into measurable signals;

dual sealing means for separating said first diaphragm and said first means, and for forming a plurality of sealed cavities therebetween surrounding said pressure responsive region.

2. The transducer as recited in claim 1 wherein said first means comprises an elastic diaphragm, having a pressure responsive region thereon deflectable in response to the local pressure, wherein said pressure responsive region is maintained in vertical alignment with the pressure responsive region of said first diaphragm.

3. The transducer as defined in claim 2 wherein said elastic diaphragm is an electrically insulating material.

4. The transducer as defined in claim 3 wherein said elastic diaphragm is a member having a substantial planar inner surface disposed adjacent to said cavities and having at least one electrically conductive electrode thereon forming the plates of at least one pressure responsive capacitor.

5. The transducer as defined in claim 3 or 4 wherein said diaphragms are quartz and said annular seals are a glass frit having thermal characteristics similar to the thermal characteristics of quartz.

6. The transducer as defined in claim 5 wherein said first means includes a second diaphragm having a pressure responsive region thereon and deflectable in response to the local pressure.

7. The transducer as defined in claim 1 where said dual sealing means comprises a pair of concentrically situated annular seals.

8. The transducer as defined in claim 7 wherein at least one of said cavities is pressurized to a specific pressure level.

9. The transducer as defined in claim 8 wherein the volumes between said annular seals and between said first diaphragm and said first means is pressurized to said same pressure level.

10. The transducer as defined in claims 8 or 9 wherein said pressure level includes a specified degree of vacuum pressure.