Pressure measuring device

• US 4,262,540 A
• Filed: 10/25/1979
• Issued: 04/21/1981
• Est. Priority Date: 11/02/1978
• Status: Expired due to Term

• Current Assignee: Research-Cottrell Technologies, Inc.
• Original Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Inventors: Yasuhara, Takeshi, Tamai, Mitsuru
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US06/088,423
• Time in Patent Office: 544 Days
• Field of Search: 73/718, 73/724, 73/708, 361/283
• US Class Current: 73/718
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

A pressure sensor the output of which is substantially immune from errors caused by temperature variation or exteriorly applied forces. An insulating disc with metal foil electrodes on the flat surfaces thereof is disposed in an inner cylinder housing between a pressure measuring diaphragm and a reference electrode plate. A first measurement pressure is applied directly to the opposite side of the diaphragm and a second measurement pressure is applied to the side adjacent the insulating disc via a soft rubber diaphragm and an insulating liquid which fills the space between the soft rubber diaphragm and measuring diaphragm extending through apertures in the inner cylinder and insulating disc. The difference pressure is determined by measuring the capacitance difference between capacitors formed by the reference electrode plate and the metal foil layer adjacent thereto and the measuring diaphragm and the metal foil layer adjacent thereto.

Claims

1. A pressure measuring device comprising:

a detecting section including an inner cylinder;

a disc-shaped diaphragm base having a through-hole extending from one end face thereof to the other end face thereof, said diaphragm base being mounted on one end face of said inner cylinder;

a pressure measuring diaphragm mounted on one end face of said diaphragm base in said inner cylinder;

a disc-shaped insulator having a through-hole extending from one end face thereof to the other end face thereof and two metal foil electrodes provided respectively on said two end faces thereof, said insulator being positioned in said inner cylinder in such a manner that the distance between one of said electrodes and said pressure measuring diaphragm is maintained at a first predetermined value; and

a disc-shaped reference electrode plate having a through-hole extending from one end face thereof to the other end face thereof, said reference electrode plate being mounted on the other end face of said inner cylinder in such a manner that the distance between the one end face thereof and the other electrode on the other end face of said insulator is maintained at a second predetermined value;

an outer cylinder having at a first end thereof a bottom portion with a through-hole, said detecting section being positioned in said outer cylinder with said diaphragm base directed towards said bottom portion;

a seal diaphragm closing a second end of said outer cylinder, a first measurement pressure being applied to said seal diaphragm;

a tubular member attached to said outer cylinder at said through-hole of said outer cylinder and said diaphragm base at said through-hole of said diaphragm base for introducing a second measurement pressure into a first space defned by said diaphragm base and said pressure measuring diaphragm;

a sealed space being provided by said outer cylinder and said seal diaphragm with the exception of said first space filled with an insulating liquid.

2. A pressure measuring device as claimed in claim 1 wherein said inner cylinder, said diaphragm base, said pressure measuring diaphragm, said insulator and said reference electrode plate are made of materials which have substantially equal thermal expansion coefficients.

3. A pressure measuring device as claimed in either claim 1 or 2 wherein the elastic hardness of said seal diaphragm is several tens to several hundreds of times as soft as that of said pressure measuring diaphragm.

4. A pressure measuring device as claimed in either claim 1 or 2 further comprising first and second conductive leads extending through a through-hole in said outer cylinder and means for hermetically sealing said leads in said through-hole.

5. A pressure measuring device comprising:

a conductive housing;

an insulating member having first and second flat parallel surfaces and a through-hole therethrough and with said first surface disposed parallel to a wall of said housing;

first and second conductors disposed respectively on said first and second parallel surfaces;

a conductive diaphragm disposed in said housing with a first side thereof parallel to said second surface;

means for supplying a first measurement pressure to a second side of said diaphragm opposite said first side;

means for supplying a second measurement pressure to a space between said first surface of said insulating member and said wall of said housing; and

wherein said housing, said diaphragm and said insulating member have substantially equal thermal expansion coefficients.

6. A pressure measuring device as claimed in claim 5 wherein said means for supplying said second measurement pressure comprises a soft, flexible diaphragm and an insulating liquid disposed in said space.