Pressure sensor

• US 7,779,698 B2
• Filed: 11/08/2007
• Issued: 08/24/2010
• Est. Priority Date: 11/08/2007
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Willcox, Charles R.
• Primary Examiner(s): Allen; Andre J
• Application Number:
  US11/983,414
• Publication Number:
  US 20090120195A1
• Time in Patent Office: 1,020 Days
• Field of Search: 737/16, 737/18, 737/24, 737/36
• US Class Current: 73/716
• CPC Class Codes: G01F 1/383 with electrical or electro-mechanical indication
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

A pressure transmitter is provided. The pressure transmitter includes a pressure sensor including a pair of process fluid pressure ports each having a deflectable diaphragm. A first variable capacitor is disposed within the pressure sensor and has a capacitance that varies with differential pressure between the process fluid ports. A second variable capacitor is disposed within the pressure sensor and has a capacitance that varies with line pressure.

Claims

1. A pressure transmitter comprising:

a pressure sensor including;

a pair of process fluid pressure ports, each port having a deflectable diaphragm adapted for exposure to a process fluid, a first deflectable diaphragm being coupled to a first beam and a second deflectable diaphragm being coupled to a second beam;

a crossbeam spanning the first and second beams and having a paddle member depending therefrom the paddle member having a plurality of capacitive plates, each of the capacitive plates forming a part of a different variable capacitor;

a first variable capacitor disposed within the pressure sensor, and having a capacitance that varies with differential pressure between the process fluid ports, the first variable capacitor being formed at least in part by one of the plurality of capacitive plates;

a second variable capacitor disposed within the pressure sensor, and having a capacitance that varies with line pressure, the second variable capacitor being formed by another of the plurality of capacitive plates;

a loop communicator coupleable to a process communication loop and configured to communicate over the loop;

a controller coupled to the loop communicator; and

measurement circuitry coupled to the controller and to the pressure sensor to provide at least one of an indication of differential pressure and line pressure over the process communication loop.

2. The pressure transmitter of claim 1, and further comprising a power module coupleable to the process communication loop, and configured to wholly power the pressure transmitter with energy received from the process communication loop.

3. The pressure transmitter of claim 1, wherein the loop communicator is configured to communicate is accordance with a process industry protocol.

4. The pressure transmitter of claim 1, wherein the pair of deflectable diaphragms are axially aligned with one another.

5. The pressure transmitter of claim 4, wherein the deflectable diaphragms are coupled to one another by a solid strut.

6. The pressure transmitter of claim 1, wherein the pair of deflectable diaphragms are disposed in substantially the same plane.

7. The pressure transmitter of claim 1, wherein the deflectable diaphragms are coupled to one another by a solid strut.

8. The pressure transmitter of claim 7, wherein the strut includes a flange configured to inhibit overpressure deflection.

9. The pressure transmitter of claim 1, wherein differential pressure changes between the pair of process fluid pressure ports generates rotation of the paddle member.

10. The pressure transmitter of claim 1, wherein the line pressure represents the pressure from one of the process fluid pressure ports.

11. A pressure transmitter comprising:

a pressure sensor including;

a pair of process fluid pressure ports, each port having a deflectable diaphragm adapted for exposure to a process fluid;

a first beam coupled to a first deflectable diaphragm, and a second beam coupled to the second deflectable diaphragm;

a strain sensitive element operably coupled to the first and second beams and configured to have an electrical parameter that changes with strain;

a variable capacitor formed between a pair of capacitive plates, the first plate being fixedly mounted adjacent the first and second deflectable diaphragms, and the second plate being operably coupled to one of the first and second beams;

a loop communicator coupleable to a process communication loop and configured to communicate over the loop;

a controller coupled to the loop communicator; and

measurement circuitry coupled to the controller and to the pressure sensor to provide at least one of an indication of differential pressure and line pressure over the process communication loop.

12. A pressure sensor comprising:

a pair of process fluid pressure ports, each port having a deflectable diaphragm adapted for exposure to a process fluid;

a first variable capacitor disposed within the pressure sensor, and having a capacitance that varies with differential pressure between the process fluid ports, the first variable capacitor being formed by at least one capacitive plate that is operably coupled to at least one of the deflectable diaphragms; and

a second variable capacitor disposed within the pressure sensor, and having a capacitance that varies with line pressure, the second variable capacitor being formed by at least one capacitive plate that is operably coupled to at least one of the deflectable diaphragms; and

wherein each of the deflectable diaphragms is coupled to a respective vertical beam and cantilever beam portion, each cantilever beam portion being coupled to a respective angled portion having a capacitive plate disposed on the angled portion, the capacitive plates on the angled portion forming the first variable capacitor, at least one cantilever beam portion having an additional capacitive plate disposed on a bottom surface and cooperating with a fixed capacitive plate located adjacent the deflectable diaphragms to form the second variable capacitor.

13. The pressure sensor of claim 12, wherein the pair of deflectable diaphragms are axially aligned with one another.

14. The pressure sensor of claim 13, wherein the deflectable diaphragms are coupled to one another by a solid strut.

15. The pressure sensor of claim 12, wherein the pair of deflectable diaphragms are disposed in substantially the same plane.

16. The pressure sensor of claim 12, wherein the deflectable diaphragms are coupled to one another by a solid strut.

17. The pressure sensor of claim 16, wherein the strut includes a flange configured to inhibit overpressure deflection.

18. A pressure sensor comprising:

a pair of process fluid pressure ports, each port having a deflectable diaphragm adapted for exposure to a process fluid;

a first beam coupled to a first deflectable diaphragm, and a second beam coupled to the second deflectable diaphragm;

a strain sensitive element operably coupled to the first and second beams and configured to have an electrical parameter that changes with strain; and

a variable capacitor formed between a pair of capacitive plates, the first plate being fixedly mounted adjacent the first and second deflectable diaphragms, and the second plate being operably coupled to one of the first and second beams.

19. A pressure sensor comprising:

a pair of process fluid pressure ports, each port having a deflectable diaphragm adapted for exposure to a process fluid;

a first variable capacitor disposed within the pressure sensor, and having a capacitance that varies with differential pressure between the process fluid ports, the first variable capacitor being formed by at least one capacitive plate that is operably coupled to at least one of the deflectable diaphragms;

a second variable capacitor disposed within the pressure sensor, and having a capacitance that varies with line pressure, the second variable capacitor being formed by at least one capacitive plate that is operably coupled to at least one of the deflectable diaphragms; and

wherein each of the deflectable diaphragms is coupled to a respective vertical beam and cantilever beam portion, each cantilever beam portion having a capacitive plate on an undersurface, wherein one vertical beam is shorter than the other vertical beam so that the cantilever beam portions overlap one another, and wherein the cantilever beam portion coupled to the shorter vertical beam has a capacitive plate on its upper surface to cooperate with the capacitive plate on the other cantilever beam portion to form a first variable capacitor, and a capacitive plate is fixedly mounted adjacent the deflectable diaphragms to cooperate with the capacitive plate on the undersurface of the cantilever beam portion attached to the shorter vertical beam to form the second variable capacitor.