Method for making a dynamic pressure sensor and a pressure sensor made according to the method

• US 5,325,720 A
• Filed: 10/07/1993
• Issued: 07/05/1994
• Est. Priority Date: 10/07/1993
• Status: Expired due to Fees

• Current Assignee: National Aeronautics and Space Administration (Government of the United States of America)
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Robbins, William E., Robins, Glenn M., Zuckerwar, Allan J.
• Primary Examiner(s): Woodiel, Donald
• Application Number:
  US08/138,046
• Time in Patent Office: 271 Days
• Field of Search: 73/756, 73/147, 73/715-728, 73/167, 92/103 M, 92/5 R, 29/621.1, 29/25.41, 29/454, 29/595
• US Class Current: 73/756
• CPC Class Codes: G01L 23/12 by changing capacitance or inductance
• CPC Class Codes: Y10T 29/49877 of flexible wall, expansible chamber devices [e.g., bellows]

Abstract

A method for providing a perfectly flat top with a sharp edge on a dynamic pressure sensor using a cup-shaped stretched membrane as a sensing element. First, metal is deposited on the membrane and surrounding areas. Next, the side wall of the pressure sensor with the deposited metal is machined to a predetermined size. Finally, deposited metal is removed from the top of the membrane in small steps, by machining or lapping while the pressure sensor is mounted in a jig or the wall of a test object, until the true top surface of the membrane appears. A thin indicator layer having a color contrasting with the color of the membrane may be applied to the top of the membrane before metal is deposited to facilitate the determination of when to stop metal removal from the top surface of the membrane.

Claims

1. A method for making a dynamic pressure sensor having a flat sensing surface with a sharp edge, comprising the steps of:

(a) providing a dynamic pressure sensor with a stretched metal membrane in the form of an inverted cup with a flat top surface and rounded edge;

(b) depositing metal on said membrane along said rounded edge; and

(c) machining said deposited metal to form a substantially cylindrical side wall of predetermined diameter and a flat top surface flush with the top surface of said membrane.

2. A method for making a dynamic pressure sensor having a flat sensing surface with a sharp edge according to claim 1, wherein said metal membrane and said deposited metal are both made from nickel.

3. A method for making a dynamic pressure sensor having a flat sensing surface and a sharp edge according to claim 1, further comprising the steps of:

(d) applying a thin indicator layer having a color different from that of the membrane before metal is deposited on said membrane; and

(e) machining and lapping the flat top of said deposited metal until said indicator layer has been removed.

4. A dynamic pressure sensor, comprising:

(a) a pressure sensor body having a tubular top and a substantially cylindrical upper side wall;

(b) an inverted cup shaped membrane fitted over said tubular top and bonded to said upper side wall;

(c) means for stretching a top surface of said membrane, whereby said top surface forms a flat prestressed area with a rounded edge; and

(d) a metal fillet deposited on said rounded edge and machined to form a sharp edge flush with said top surface.

5. A dynamic pressure sensor according to claim 4, wherein said membrane is made from nickel foil and said metal fillet is made from nickel electro-deposited on said membrane.

6. A method for mounting a dynamic pressure sensor flush with a test surface, comprising the steps of:

(a) providing an opening through the test surface;

(b) providing a dynamic pressure sensor with a stretched metal membrane, said membrane forming a flat top surface with a rounded edge and a side wall fitting loosely inside said opening;

(c) applying a thin indicator layer having a color different from that of the membrane to the top surface of said membrane;

(d) depositing a layer of metal on said side wall and on said metal membrane over said indicator layer;

(e) machining said deposited layer of metal to form a new side wall fitting tightly in said opening and having a flat top;

(f) mounting said pressure sensor adjustably in said opening with said flat top protruding slightly beyond said test surface;

(g) removing deposited metal protruding beyond said test surface in small steps; and

(h) fixing said pressure sensor in place when said indicator layer has been removed.

7. A method for mounting a dynamic pressure sensor flush with a test surface according to claim 6, wherein said metal membrane and said deposited metal are both made of nickel.

8. A method for mounting a dynamic pressure sensor flush with a test surface according to claim 6, wherein the final removal of deposited metal and said indicator layer is made by lapping.