DIFFERENTIAL PRESSURE TRANSDUCER

• US 3,800,413 A
• Filed: 07/26/1971
• Issued: 04/02/1974
• Est. Priority Date: 10/27/1969
• Status: Expired due to Term

• Current Assignee: Roger L. Frick
• Original Assignee: Roger L. Frick
• Inventors: Frick, Roger L.
• Primary Examiner(s): Lanham, Charles W.
• Assistant Examiner(s): Crane, D. C.
• Application Number:
  US05/164,861
• Time in Patent Office: 981 Days
• Field of Search: 29/593,594,595,472.9,434,454,463,499,503,631,592 73/398R,398C,406,407,408,398AR 317/246
• US Class Current: 29/592.1
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

A differential pressure transducer of the capacitor type utilizing isolation diaphragms for sensing the differential pressure directly, and having a central chamber with a sensing diaphragm in the central chamber. The central chamber is filled with oil or a suitable liquid which transmits pressure from the isolation diaphragms to the sensing diaphragm. The sensing diaphragm forms a capacitor plate, and the walls of the chamber adjacent to the sensing diaphragm also form capacitor plates. The pressures are transmitted to the sensing diaphragm through the oil so that only differential pressure is sensed between the two isolation diaphragms. The sensing diaphragm and its chamber are made so that any excessive pressure causes the sensing diaphragm to bottom out against its mounting chamber surfaces. The unit is made extremely stable, by using a relatively massive metal housing with a glass center portion fused thereto, and depositing the metallic capacitor plate material right onto the glass surfaces which form the sensing chamber.

Claims

1. A method of constructing a pressure sensing cell assembly of the capacitor type including the steps of providing massive metal housing sections, at least one of said sections having an internal cavity, filling said cavity with an insulation material and fusing said material to the metal surfaces defining said cavity, forming a concave surface in said insulation material after it has been fused to the cavity surface, depositing a layer of electrical conductive material on said concave surface to form a first capacitor plate, enclosing the concave surface with a sensing diaphragm sealed to said one housing section to form a sensing chamber, said sensing diaphragm forming a second capacitor plate, forming a second chamber in said one housing section, closing said second chamber with a second diaphragm, providing fluid passage means between said first and second chambers, and filling said first and second chambers and said fluid passage means with a fluid to transmit pressure on said second diaphragm to said sensing diaphragm.

2. A method of constructing a pressure sensing cell assembly of the capacitor type including the steps of providing massive metal housing sections, each of said housing sections having an internal cavity, filling said cavities with an insulation material and fusing said material to the metal surfaces defining said cavities, forming concave surfaces in said insulation material, providing electrically conductive tubular members opening to said concave surfaces and passing out the walls of said housing sections, depositing a separate layer of electrical conductive material on each of said concave surfaces electrically connected to said tubular members, sealing said sensing diaphragm means to said housing sections to form first and second sensing chambers, said housing sections having isolation chambers defined therein with isolation diaphragm means, providing fluid passage means opening between each of said isolation chambers and a corresponding sensing chamber, filling said isolation chambers, said fluid passage means and said sensing chambers with a fluid through said tubular members, sealing said tubular members after the filling step, and connecting electrical lead means to said tubular members after they have been sealed.

3. A method of constructing a pressure sensing cell assembly of the capacitor type including the steps of providing massive metal housing sections, at least one of said sections having an internal cavity, filling said cavity with an insulation material and fusing said material to the metal surfaces defining said cavity, forming a concave surface in said insulation material after it has been fused to the cavity surface, depositing a layer of electriCal conductive material on said concave surface to form a first capacitor plate, enclosing the concave surface with a sensing diaphragm sealed to said one housing section, said sensing diaphragm forming a second capacitor plate, providing a second chamber closed by a second diaphragm on said one section, providing fluid passage means between the area enclosed between the concave surface and the sensing diaphragm and said second chamber, filling said second chamber, said fluid passage means and the area enclosed by said sensing diaphragm with fluid to transmit pressure on said second diaphragm to said sensing diaphragm.

4. A method of making a differential capacitive pressure transducer having a sensing cell of the capacitive type and an outer housing forming a pair of pressure chambers, including the steps of providing two sensing cell sections, each of said cell sections having a first chamber defined in one surface thereof, a spaced second chamber and fluid passage means extending between said first and second chambers of each cell section, placing a sensing diaphragm between said cell sections to close both of said first chambers, closing each of said second chambers with second diaphragms, filling said first and second chambers and said fluid passage means on each cell section with fluid to transmit pressure on said second diaphragm to said sensing diaphragm, providing a wall member, clamping said sensing cell sections together against said wall member so that said sensing diaphragm is clamped at a first clamping stress level, and clamping said outer housing to support portions of said wall member other than those clamping the sensing cell sections to mechanically support said outer housing on the support portions at a desired clamping force before the outer housing is pressed against said cell sections to thereby support said outer housing without substantially changing the clamping stress on said diaphragm.