Capacitance pressure sensor

• US 4,389,895 A
• Filed: 07/27/1981
• Issued: 06/28/1983
• Est. Priority Date: 07/27/1981
• Status: Expired due to Term

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Rud, Stanley E. Jr.
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US06/287,307
• Time in Patent Office: 701 Days
• Field of Search: 73/724, 73/718, 361/283
• US Class Current: 73/724
• CPC Class Codes: G01L 19/02 Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means for aneroid barometers G01L7/14
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

A capacitive pressure sensor has a diaphragm means a portion of which is conductive which forms a first capacitor electrode. The sensor also has a reference disc means a portion of which is conductive which forms a second capacitive electrode. The diaphragm means and the reference disc means are supported in a spaced, over-lying relationship to each other by a peripheral spacer means. Responsive to pressure, the diaphragm means deflects relative to the reference disc means thus changing the capacitive spacing of the diaphragm means and the reference disc means. The diaphragm means, reference disc means and spacer means are formed from substantially the same material. The spacer means is disposed between the diaphragm means and the reference disc means adjacent their outer edges and the diaphragm means, reference disc means and spacer means are then fused together.

Claims

1. Apparatus for measuring pressure comprising:

diaphragm means for deflection under pressure having a first side for application of first pressure thereto, and a second side for application of a second pressure, wherein at least a portion of the diaphragm means is conductive thus forming a first capacitor electrode;

reference disc means having a passageway therethrough for communicating the first pressure to one side of the diaphragm means and having a first disc side and a second disc side, wherein at least a portion of the reference disc means is conductive thus forming a reference capacitor electrode in electrical communication with the first capacitor electrode, and

spacer means for supporting the diaphragm means adjacent its edges in a spaced relationship from the reference disc means,

characterized in that the spacer means is formed from substantially the same material as the diaphragm means and the reference disc means and is disposed therebetween, and wherein the diaphragm means, the reference disc means and the spacer means are then fused together.

2. Apparatus according to claim 1 wherein the spacer means is deposited adjacent the periphery of at least one of the diaphragm means and the reference disc means.

3. Apparatus according to claim 2 wherein the spacer means is sputtered adjacent the periphery of at least one of the diaphragm means and the reference disc means.

4. Apparatus according to claim 2 wherein the spacer means is vapor deposited adjacent the periphery of at least one of the diaphragm means and the reference disc means.

5. Apparatus according to claim 2 wherein the spacer means is evaporatively deposited adjacent the periphery of at least one of the diaphragm means and the reference disc means.

6. Apparatus according to claim 1 wherein the spacer means is integrally formed adjacent the periphery of at least one of the diaphragm means or the reference disc means.

7. Apparatus according to claim 1 further comprising support block means fused to the reference disc means adjacent its periphery and having a bore for communicating the first pressure to the first side of the diaphragm means, and wherein the support block means provides support for the diaphragm means and the reference disc means.

8. Apparatus according to claim 7 further comprising:

a housing for enclosing the apparatus and having port means for communicating the second pressure to the second side to the diaphragm means; and

mounting ring means for attaching the support block means to the housing.

9. Apparatus according to claim 8 wherein the mounting ring means together with the housing provides a pressure barrier to separate the first and the second pressures.

10. Apparatus according to claim 7 wherein the diaphragm means and the reference disc means have a thickness D1 and RD1 respectively and wherein RD1 is less than D1.

11. Apparatus according to claim 10 wherein the thickness RD1 is related to thickness D1 to at least partially compensate the acceleration sensitivity differences resulting from supporting the edge of the diaphragm means relative to the support means on one side only while supporting the edge of the reference disc means on both sides thereof relative to the reference disc means.

12. Apparatus according to claim 7 wherein the diaphragm means, the reference disc means, the spacer means and the support means are formed from the same electrically non-conductive material.

13. Apparatus according to claim 8 wherein the dielectric material is selected from a group consisting of fused silica, glass, or other non-conductive good spring property material.

14. Apparatus according to claim 1 wherein the conductive portion of the diaphragm means and the conductive portion of the reference disc means are formed by depositing a conductive material on a portion of the electrically non-conductive material.

15. Apparatus according to claim 14 wherein the conductive material is deposited on a portion of the first side of the diaphragm means and on a portion of the second side of the reference disc means.

16. Apparatus according to claim 15 wherein the first bore in the reference disc means comprises a plated through hole for electrically coupling the conductive portion of the reference disc means to suitable circuitry.

17. Apparatus according to claim 16 wherein the support block means has circuit conduction paths deposited thereon and suitable leadwire means are coupled from such paths to the conductive material on the diaphragm means and the reference disc means respectively.

18. Apparatus according to claim 17 further comprising excitation and detection means supported on the support block means and electrically coupled to the diaphragm means and the reference disc means for exciting and detecting the signal from the diaphragm means and the reference disc means.

19. Apparatus according to claims 1, 7, or 17 wherein a temperature detection means is supported on at least one of the support block means, diaphragm means and reference disc means for sensing the temperature thereof.