In-line annular seal-based pressure device

• US 7,096,738 B2
• Filed: 03/18/2004
• Issued: 08/29/2006
• Est. Priority Date: 03/18/2004
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Schumacher, Mark
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Bonanto, George P
• Application Number:
  US10/804,935
• Publication Number:
  US 20050204822A1
• Time in Patent Office: 894 Days
• Field of Search: 73/491, 738/616.3, 737/18, 738/615.2
• US Class Current: 73/718
• CPC Class Codes: G01F 1/383 with electrical or electro-mechanical indication
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

A pressure sensor for measuring a pressure of a process fluid includes a vessel, an electrode and a diaphragm. The vessel receives the process fluid. The electrode is integral with an inner wall of the vessel. The diaphragm extends at least partially over the electrode and is configured to move relative to the electrode in response to the pressure of the process fluid. An electrical capacitance between the electrode and the diaphragm is related to the pressure of the process fluid.

Claims

1. A pressure sensor for measuring a pressure of a process fluid, comprising:

a contiguous electrically conductive vessel for receiving the process fluid;

an electrical insulator extending over an inner wall of the electrically conductive vessel;

an electrode integral with the electrical insulator; and

a diaphragm that extends at least partially over the electrode and mates flush with the inner wall of the vessel and generally parallel with flow of process fluid through the vessel and that is configured to move relative to the electrode in response to the pressure of the process fluid;

wherein an electrical capacitance between the electrode and the diaphragm is related to a pressure of the process fluid and wherein the diaphragm defines a cavity between the diaphragm and the electrode, the cavity containing a vacuum.

2. The pressure sensor of claim 1 wherein the insulator and electrode extend partially around the inner wall of the vessel.

3. The pressure sensor of claim 2 wherein the diaphragm extends partially around the inner wall of the vessel.

4. The pressure sensor of claim 1 and further comprising:

a temperature sensor integral with the inner wall to measure a fluid temperature and to generate a temperature signal indicative of the fluid temperature.

5. The pressure sensor of claim 4 and further comprising:

processing electronics adapted to produce a pressure signal that is a function of the temperature signal.

6. The pressure sensor of claim 1 wherein the insulator and electrode extend completely around the inner wall of the vessel.

7. The pressure sensor of claim 6 wherein the diaphragm extends completely around the inner wall of the vessel.

8. The pressure sensor of claim 1 and further comprising:

a measurement circuit adapted to produce a pressure signal based on the electrical capacitance.

9. The pressure sensor of claim 1 and further comprising:

a wireless transceiver mounted to a housing and electrically connected to the electrode to wireless transmit the pressure signal.

10. The pressure sensor of claim 1 wherein the electrode and the diaphragm form a first capacitor, and further comprising:

a flow restrictive element extending from the inner wall of the vessel into the process fluid; and

a second capacitor having a second electrode integral with the inner wall and a second diaphragm that extends at least partially over the second electrode and that is configured to move relative to the second electrode in response to the pressure of the process fluid.

11. The pressure sensor of claim 1 wherein the diaphragm extends away from the inner wall into the process fluid.

12. The pressure sensor of claim 1 wherein the diaphragm is flush with the inner wall of the vessel and the insulator and electrode are recessed into the inner wall.

13. The pressure sensor of claim 1 wherein the electrical insulator comprises glass.

14. The pressure sensor of claim 1 wherein the electrical insulator comprises ceramic.

15. The pressure sensor of claim 1 wherein the diaphragm is sealed to the vessel by a weld.

16. A differential pressure sensor for measuring a differential pressure of a process fluid in a conduit, comprising:

a flow restriction element integral with a conductive inner wall of the conduit and adapted to produce a pressure drop when placed in-line with a fluid flow;

a first electrical insulator integral with a contiguous section of the conductive inner wall of the conduit;

a first capacitor having a first capacitance and including a first electrode integral with the first electrical insulator and positioned upstream from the flow restriction element and in-line with the process fluid the first capacitor comprising a first dielectric between the first electrode and a second electrode;

a second electrical insulator integral with the contiguous section of the conductive inner wall of the conduit;

a second capacitor having a second capacitance and including a third electrode integral with the second electrical insulator and positioned downstream from the flow restriction element and in-line with the process fluid the second capacitor comprising a second dielectric between the third electrode and a fourth electrode;

wherein the first capacitance and the second capacitance are related to the differential pressure of the process fluid and wherein each of the first dielectric and the second dielectric is a vacuum.

17. The differential pressure sensor of claim 16, further comprising:

processing electronics adapted to produce a flow rate signal that is indicative of a direction and a flow rate of the process fluid as a function of the first and the second capacitances.

18. The differential pressure sensor of claim 16, wherein the first capacitor comprises:

a diaphragm that extends at least partially over the first electrode and that is configured to move relative to the first electrode in response to the pressure of the process fluid;

wherein the first capacitance is between the first electrode and the diaphragm and is related to the pressure of the process fluid.

19. The differential pressure sensor of claim 18 wherein the diaphragm is sealed to the conduit by a weld.

20. The differential pressure sensor of claim 16 wherein the flow restriction element has a narrow fluid flow passageway extending between symmetric first and second throat portions.

21. The differential pressure sensor of claim 16, further comprising:

a temperature sensor adapted to sense at least one of a temperature of the fluid flow and an operating temperature of the pressure sensor and to produce a temperature signal that is indicative of the sensed temperature.

22. The differential pressure sensor of claim 21 wherein a flow rate signal is a function of the temperature signal.

23. The differential pressure sensor of claim 16 wherein each of the first capacitor and the second capacitor extend at least partially around the inner wall of the conduit.

24. The differential pressure sensor of claim 16 wherein each of the first capacitor and the second capacitor extend entirely around the inner wall of the conduit.

25. The differential pressure sensor of claim 16 wherein the first electrical insulator and the second electrical insulator comprises glass.

26. The differential pressure sensor of claim 16 wherein the first electrical insulator and the second electrical insulator comprises ceramic.