In-line annular seal-based pressure device

• US 20050204822A1
• Filed: 03/18/2004
• Published: 09/22/2005
• 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
• Granted Patent: US 7,096,738 B2
• Time in Patent Office: Days
• 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 vessel for receiving the process fluid;

an electrode integral with an inner wall of the vessel; and

a diaphragm that extends at least partially over the electrode 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.

2. The pressure sensor of claim 1 wherein the electrode extends 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 electrode extends 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 electrical capacitance.

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

a wireless transceiver mounted to the housing and electrically connected with the annular capacitor for wireless transmitting the pressure signal to a control and/or monitoring system.

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;

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

wherein the flow restrictive element is positioned between the first capacitor and the second capacitor to measure a first capacitance and a second capacitance such that a difference between the first and the second capacitances is a differential capacitance representative of a differential 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 fluid flow conduit and the electrode is recessed into the inner wall.

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

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

a first capacitor integral with the inner wall of the conduit and positioned upstream from the flow restriction element and in-line with the process fluid; and

a second capacitor integral with the inner wall of the conduit and positioned downstream from the flow restriction element and in-line with the process fluid;

wherein in a first capacitance and a second capacitance are related to the pressure of the process fluid.

14. The differential pressure sensor of claim 13, 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.

15. The differential pressure sensor of claim 13, wherein the first capacitor and the second capacitor each comprises:

an electrode integral with an inner wall of the conduit; and

a diaphragm that extends at least partially over the electrode 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 the pressure of the process fluid.

16. The differential pressure sensor of claim 13 wherein the flow restriction element has a narrow fluid flow passageway extending between symmetric first and second throat portions.

17. The differential pressure sensor of claim 13, 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.

18. The differential pressure sensor of claim 17 wherein the flow rate signal is further a function of the temperature signal.

19. The differential pressure sensor of claim 13 wherein each of the first capacitor and the second capacitor extend at least partially around the inner wall of the conduit.

20. The differential pressure sensor of claim 13 wherein each of the first capacitor and the second capacitor extend entirely around the inner wall of the conduit.

21. A flow meter adapted to measure a pressure and a flow direction of a process fluid within a conduit the flow meter comprising:

a first capacitive pressure sensor adapted to generate a first capacitance signal;

a second capacitive pressure sensor adapted to generate a second capacitance signal; and

a flow restrictive element positioned within the conduit and between the first and the second capacitive pressure sensors and adapted to cause a pressure drop in the conduit;

wherein the first and the second capacitance signals are representative of a first and a second pressure of the process fluid such that the first and the second capacitance signals may be subtracted to calculate a differential capacitance representative of a differential pressure.

22. The flow meter of claim 21 wherein each capacitive pressure sensor comprises:

an electrode integral to an inner wall of the conduit; and

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

wherein in an electrical capacitance between the electrode and the diaphragm is related to the pressure of the process fluid.

23. The flow meter of claim 22 wherein the diaphragm is flush with the inner wall of the fluid flow conduit and the electrode is recessed into the wall.

24. The flow meter of claim 22 wherein the diaphragm extends into the process fluid and the electrode is flush with the inner wall of the conduit.

25. The flow meter of claim 22 wherein the electrode extends partially around the inner wall of the conduit.

26. The flow meter of claim 25 wherein the diaphragm extends partially around the wall of the conduit.

27. The flow meter of claim 21 further comprising:

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

28. The flow meter of claim 27 further comprising:

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

29. The flow meter of claim 22 wherein the electrode extends completely around the inner wall of the conduit.

30. The flow meter of claim 29 wherein the diaphragm extends completely around the inner wall of the conduit.

31. The flow meter of claim 22 further comprising:

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

32. The flow meter of claim 21 further comprising:

a wireless transceiver mounted to the conduit and electrically connected with the first and second capacitive pressure sensors for wireless transmission of the differential pressure to a control and/or monitoring system.

33. The flow meter of claim 21 further comprising:

a temperature sensor embedded within an insulator of the first capacitive pressure sensor to measure a device temperature and to generate a temperature signal indicative of the device temperature.