Differential pressure sensor with high pressure capabilities

• US 9,857,259 B2
• Filed: 09/30/2014
• Issued: 01/02/2018
• Est. Priority Date: 09/30/2014
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Broden, David Andrew, Willcox, Charles Ray, Harasyn, Donald Edward
• Primary Examiner(s): Tran, Tony
• Application Number:
  US14/501,310
• Publication Number:
  US 20160091379A1
• Time in Patent Office: 1,190 Days
• CPC Class Codes: G01L 11/025 using a pressure-sensitive optical fibre
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 19/0038 being part of the housing other details about the housing G01L19/14
• CPC Class Codes: G01L 19/0084 to the outside of the housing other details about the housing see G01L19/14
• CPC Class Codes: G01L 19/0681 Protection against excessive heat
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

A capacitance-based pressure sensor for measuring a process variable includes a metal sensor body, a diaphragm disposed within a cavity of the metal sensor to form a deflectable capacitor plate, and an insulator extending through the metal sensor body from an end wall to the cavity. The pressure sensor further includes an isolation tube in fluid connection with the cavity, the isolation tube extending into the insulator through the end wall, a stationary capacitor plate on a surface of the insulator in the cavity, the stationary capacitor plate spaced from the diaphragm, and an electrical lead wire connected to the stationary capacitor plate and extending through the insulator parallel to the isolation tube and exiting the insulator at the end wall. A fill fluid is within the isolation tube and the cavity to apply pressure to the diaphragm.

Claims

1. A capacitance-based differential pressure sensor for measuring a process variable, the pressure sensor comprising:

a first cell half comprising;

a first metal body having a planar first exterior end wall, a first interior wall, and a cylindrical side wall perpendicular to the first exterior end wall;

a first insulator that extends from a central portion of the first exterior end wall through the first metal body to a first surface at the first interior wall without extending to the cylindrical side wall; and

a first capacitor plate positioned on the first insulator at the first surface;

a second cell half comprising;

a second metal body having a planar second exterior end wall, a second interior wall, and a cylindrical side wall perpendicular to the second exterior end wall;

a second insulator that extends from a central portion of the second exterior end wall through the second metal body to a second surface at the second interior wall without extending to the cylindrical side wall; and

a second capacitor plate positioned on the second insulator at the second surface;

a diaphragm connected at a joint between the first interior surface of the first cell half and the second interior surface of the second cell half;

a first isolation tube with a first end in fluid communication with a first interior cavity and extending through the first insulator to exit the first cell half at the first exterior end wall;

a second isolation tube with a first end in fluid communication with a second interior cavity and extending through the second insulator to exit the second cell half at the second exterior end wall;

a first electrical lead wire with a first end in contact with the first capacitor plate and extending through the first insulator parallel to the first isolation tube to exit the first cell half parallel to the first isolation tube at the first exterior end wall;

a second electrical lead wire with a first end in contact with the second capacitor plate and extending through the second insulator parallel to the second isolation tube to exit the second cell half parallel to the second isolation tube at the second exterior end wall;

a third electrical lead wire with a first end in contact with the first cell half or the second cell half;

a first fill fluid within the first isolation tube and the first interior cavity; and

a second fill fluid within the second isolation tube and the second interior cavity,

wherein at a point where the first isolation tube and the first electrical lead wire exit the first cell half they are substantially perpendicular to the first exterior end wall, and at a point where the second isolation tube and the second electrical lead wire exit the second cell half they are substantially perpendicular to the second exterior end wall.

2. The pressure sensor of claim 1, wherein the diaphragm is electrically connected through one of the first and second metal bodies to the third electrical lead wire.

3. The pressure sensor of claim 1, including a plurality of first electrical lead wires, and a plurality of second electrical lead wires.

4. The pressure sensor of claim 1, wherein the first isolation tube includes a second end that terminates adjacent a first isolation diaphragm, and wherein the second isolation tube includes a second end that terminates adjacent a second isolation diaphragm.

5. The pressure sensor of claim 1, wherein the first electrical lead wire, the second electrical lead wire, and the third electrical lead wire each have a second end connected to circuitry to produce a differential pressure signal output.

6. The pressure sensor of claim 1, wherein the first metal body is annular and surrounds the first insulator, and wherein the second metal body is annular and surrounds the second insulator.

7. The pressure sensor of claim 1, wherein the insulator is a glass or ceramic-based material.

8. The pressure sensor of claim 1, wherein the first and second surfaces of the first and second interior walls, respectively, are curved surfaces.

9. A pressure sensor comprising:

a cell body having a planar first exterior end wall, a planar second exterior end wall, a cylindrical side wall perpendicular to the first exterior end wall and the second exterior end wall, a first interior wall, and a second interior wall, the first and second interior walls facing one another and defining an interior cavity, wherein the cell body includes a first metal cell half surrounding a first insulator region that extends from a central portion of the first exterior end wall to the interior cavity without extending to the cylindrical side wall and forms a first surface of the first interior wall, and a second metal cell half surrounding a second insulator region that extends from a central portion of the second exterior end wall to the interior cavity without extending to the cylindrical side wall and forms a second surface of the second interior wall;

a deflectable diaphragm connected at an outer periphery between the first and second interior walls, the diaphragm separating the interior cavity into a first cavity and a second cavity;

a first fluid passage extending through the first insulator region from the first cavity to the first exterior end wall;

a second fluid passage extending through the second insulator region from the second cavity to the second exterior end wall;

a first electrode on the first surface;

a second electrode on the second surface;

a first electrical lead extending from the first electrode through the first insulator region parallel to the first fluid passage and out of the first exterior end wall; and

a second electrical lead extending from the second electrode through the second insulator region parallel to the second fluid passage and out of the second exterior end wall;

wherein at a point where the first fluid passage and the first electrical lead exit the first metal cell half they are substantially perpendicular to the first exterior end wall, and at a point where the second fluid passage and the second electrical lead exit the second metal cell half they are substantially perpendicular to the second exterior end wall.

10. The pressure sensor of claim 9, including a plurality of first electrical lead wires, and a plurality of second electrical lead wires.

11. The pressure sensor of claim 9, wherein the first surface of the first interior wall and the second surface of the second interior wall are curved surfaces.

12. The pressure sensor of claim 9, and further comprising:

a third electrical lead wire with a first end in contact with the first metal cell half or the second metal cell half, wherein the deflectable diaphragm is electrically connected through one of the first metal cell half and the second metal cell half to the third electrical lead wire.

13. The pressure sensor of claim 12, wherein the first electrical lead wire, the second electrical lead wire, and the third electrical lead wire each have a second end connected to circuitry to produce a pressure signal output.

14. The pressure sensor of claim 9, wherein the insulator is a glass or ceramic-based material.