Dual diaphragm differential pressure transducer

• US 4,735,098 A
• Filed: 03/11/1986
• Issued: 04/05/1988
• Est. Priority Date: 11/19/1985
• Status: Expired due to Term

• Current Assignee: Kavlico Corporation (Sensata Technologies Holding Plc)
• Original Assignee: Kavlico Corporation (Sensata Technologies Holding Plc)
• Inventors: Park, Kyong, Kavli, Fred
• Primary Examiner(s): WOODIEL, DONALD
• Application Number:
  US06/838,514
• Time in Patent Office: 756 Days
• Field of Search: 73/718, 73/724, 73/708, 73/720, 73/721, 361/283
• US Class Current: 73/718
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0051 using variations in ohmic resistance
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

A corrosion proof differential pressure transducer includes a central disk and two thin diaphragms mounted close to but spaced from the disk on both sides thereof, with the diaphragms being intercoupled to move together. This may be accomplished, for example, by a rod passing through a hole in the center of the central disk which is secured to each of the diaphragms; or by a fluid such as silicone oil in the space between the diaphragms and flowing through one or more holes through the central disk. At least one of the diaphragms, the central disk and the rod (when one is used) are formed of alumina, quartz, or other inert, insulating material having substantially zero mechanical hysteresis. One of the diaphragms may be a thin, tough, flexible insulating membrane. Conductive plates providing variable capacitance with changes in pressure may be mounted on the inner surface one or both of the diaphragms and on the facing surface of the central disk. Alternatively, resistive elements bonded to the inner surfaces of the diaphragms may be employed as the pressure sensing elements, as their resistance changes with flexing of the diaphragms. A housing and associated gaskets direct pressures from two different fluids to the two diaphragms, so that the differential pressure is measured.

Claims

1. A corrosion-proof pressure transducer for measuring the pressure difference between two fluids, comprising:

a central insulating base member having at least one opening and two spaced flat sides;

first and second thin substantially flat inslating diaphragms having substantially zero mechanical hysteresis;

means for mounting said diaphragms, one on each side of said base member and spaced apart from said base member at the center of said diagragms by between 0.0005 and 0.010 inch, and peripherally secured to said base member;

means for intercoupling said pair of diaphragms extending through the opening in said base member;

means responsive to the flexing of at least one of said diagragms for producing an electrical output signal substantially proportional to the differential pressure;

enclosing means having first and second input ports for applying fluid pressures from two different sources to the outer surfaces of said first and second diaphragms, respectively; and

resilient means mounted near the peripheries of said first and second diaphragms directing and limiting the fluid path from each of input ports to the associated diaphragm;

whereby the electrical output signal is a function of the difference in the fluid pressures applied to said two diaphragms.

2. A corrosion-proof pressure transducer as defined in claim 1 wherein one of said diaphragms is formed of a ceramic material, the other of said diaphragms is a very thin, tough, membrane, and wherein the intercoupling means is an insulating fluid filling said hole and the space between said diaphragms and said central base member.

3. A corrosion-proof pressure transducer as defined in claim 1 wherein said means for producing an electric signal is mounted between the inner surfaces of said two diaphragms.

4. A corrosion-proof pressure transducer as defined in claim 1 wherein said means for producing an electric signal includes resistive material bonded to the inner surface of at least one of said diaphragms having a resistance which varies with deflection of said diaphragm.

5. A corrosion-proof pressure transducer as defined in claim 1 wherein said means for producing an electric signal includes a pair of facing capacitive plates, one mounted on the inner surface of one of said diaphragms and the other mounted on said central insulating base member.

6. A corrosion-proof pressure transducer as defined in claim 1 wherein said central insulating base member and at least one of said diaphragms are made of alumina.

7. A corrosion-proof pressure transducer as defined in claim 1 wherein said diaphragm intercoupling means is an insulating fluid filling the space between said diaphragms.

8. A corrosion-proof pressure transducer for measuring the pressure difference between two fluids, comprising:

a central insulating base member having at least one opening and two spaced flat sides;

first and second thin substantially flat insulating diaphragms having substantially zero mechanical hysteresis, one of said diaphragms being a very thin flexible membrane;

means for intercoupling said pair of diaphragms extending through the opening in said base member;

means responsive to the flexing of at least one of said diaphragms for producing an electrical output signal substantially proportional to the differential pressure, said means being located between the inner surfaces of said two diaphragms where it is not exposed to the fluids being measured;

enclosing means having first and second input ports for applying fluid pressures from two different sources to the outer surfaces of said first and second diaphragms, respectively; and

resilient means mounted near the peripheries of said first and second diaphragms directing and limiting the fluid path from each of input ports to the associated diaphragm;

whereby the electrical output signal is a function of the difference in the fluid pressures applied to said two diaphragms.

9. A corrosion-proof pressure transducer as defined in claim 8 wherein one of said diaphragms is formed of a ceramic material, the other of said diaphragms is a very thin, tough, membrane, and wherein the intercoupling means is an insulating fluid filling said hole and the space between said diaphragms and said central base member.

10. A corrosion-proof pressure transducer as defined in claim 8 wherein said means for producing an electric signal is mounted between the inner surfaces of said two diaphragms.

11. A corrosion-proof pressure transducer as defined in claim 8 wherein said means for producing an electric signal includes resistive material bonded to the inner surface of at least one of said diaphragms and having variable resistance with deflection of said diaphragm.

12. A corrosion-proof pressure transducer as defined in claim 8 wherein said means for producing an electric signal includes a pair of facing capacitive plates, one mounted on the inner surface of one of said diaphragms and the other mounted on said central insulating base member.

13. A corrosion-proof pressure transducer as defined in claim 8 wherein said central insulating base member and at least one of said diaphragms are made of alumina.

14. A corrosion-proof pressure transducer as defined in claim 8 wherein said diaphragm intercoupling means is an insulating fluid filling the space between said diaphragms.

15. A corrosion-proof pressure transducer for measuring the pressure difference between two fluids, comprising:

a central insulating base member having at least one opening and two spaced flat sides;

first and second thin substantially flat insulating diaphragms having substantially zero mechanical hysteresis, one of said diaphragms being formed of a thin stiff material, and the other of said diaphragms being formed of a flexible membrane;

means for mounting said stiff diaphragm on one side of said base member and spaced apart from said base member by between 0.0005 and 0.010 inch, and peripherally secured to said base member;

means for mounting said membrane on the other side;

means for intecoupling said pair of diaphragms extending through the opening in said base member, said intercoupling means comprising an insulating fluid;

means responsive to the flexing of at least one of said diaphragms for producing an electrical output signal substantially proportional to the differential pressure;

enclosing housing means having first and second input ports extending directly through said housing directly to the outer surfaces of said first and second diaphragms, respectively; and

resilient gasket means mounted near the peripheries of said first and second diaphragms directing and limiting the fluid path from each of input ports to the associated diaphragm;

whereby the electrical output signal is a function of the difference in the fluid pressures applied to said two diaphragms.

16. A corrosion-proof pressure transducer as defined in claim 15 wherein said means for producing an electric signal is mounted between the inner surfaces of said two diaphragms.

17. A corrosion-proof pressure transducer as defined in claim 15 wherein said means for producing an electric signal includes resistive material bonded to the inner surface of at least one of said diaphragms and having variable resistance with deflection of said diaphragm.

18. A corrosion-proof pressure transducer as defined in claim 15 wherein said means for producing an electric signal includes a pair of facing capacitive plates, one mounted on the inner surface of one of said diaphragms and the other mounted on said central insulating base member.

19. A corrosion-proof pressure transducer as defined in claim 15 wherein said central insulating base member and at least one of said diaphragms are made of alumina.