DIFFERENTIAL PRESSURE SENSOR ISOLATION IN A PROCESS FLUID PRESSURE TRANSMITTER

• US 20090078054A1
• Filed: 09/20/2007
• Published: 03/26/2009
• Est. Priority Date: 09/20/2007
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Romo, Mark G.
• Granted Patent: US 7,624,642 B2
• Time in Patent Office: Days
• US Class Current: 73/717
• CPC Class Codes: G01L 13/026 involving double diaphragm
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 19/0645 using isolation membranes, specially adapted for protection

Abstract

A differential pressure transmitter includes first and second process fluid inlets. A differential pressure sensor is disposed within the transmitter and has first and second sensor inlets. A first isolator diaphragm is located proximate the first process fluid inlet and is operably coupled to the first sensor inlet through a first fill fluid volume. A second isolator diaphragm is located proximate the second process fluid inlet and is operably coupled to the second sensor inlet through a second fill fluid volume. Measurement circuitry is operably coupled to the differential pressure sensor and configured to measure an electrical parameter of the sensor and provide an indication of the measured parameter. A third fluid volume substantially surrounds the differential pressure sensor. The third fluid volume exerts a compressive force on the differential pressure sensor.

Claims

1. A differential pressure transmitter comprising:

first and second process fluid inlets;

a differential pressure sensor having first and second sensor inlets;

a first isolator diaphragm disposed proximate the first process fluid inlet and operably coupled to the first sensor inlet through a first fill fluid volume;

a second isolator diaphragm disposed proximate the second process fluid inlet and operably coupled to the second sensor inlet through a second fill fluid volume;

transmitter circuitry operably coupled to the differential pressure sensor and configured to measure an electrical parameter of the sensor and provide an indication thereof; and

a third fluid volume substantially surrounding the differential pressure sensor, the third fluid volume exerting a compressive force on the differential pressure sensor.

2. The transmitter of claim 1, wherein the differential pressure sensor is a brittle material based pressure sensor.

3. The transmitter or claim 2, wherein the brittle material based pressure sensor is a MEMS device.

4. The transmitter of claim 1, and further comprising a compensation body disposed within the third fluid volume.

5. The transmitter of claim 4, wherein the compensation body is constructed from a material having a coefficient of thermal expansion that offsets thermal effects of at least one fluid volume.

6. The transmitter of claim 1, wherein the first and second fill fluids are incompressible fluids.

7. The transmitter of claim 1, wherein the third fluid is an incompressible fluid.

8. The transmitter of claim 1, and further comprising first and second secondary isolator diaphragms, wherein the first secondary isolator diaphragm is operably coupled to the first isolator diaphragm and separates the first fill fluid volume from the third fluid volume, and wherein the second secondary isolator diaphragm is operably coupled to the second isolator diaphragm and separates the second fill fluid volume from the third fluid volume.

9. The transmitter of claim 8, wherein the first and second secondary isolator diaphragms are disposed within a capsule.

10. The transmitter of claim 1, and further comprising a line pressure sensor operably coupled to the third fluid volume and electrically coupled to the transmitter circuitry.

11. The transmitter of claim 1, wherein the transmitter is wholly powered by a process communication loop.

12. A differential pressure transmitter comprising:

A first pressure sensor having a first sensor inlet;

a second pressure sensor having a second sensor inlet;

first and second process fluid inlets;

a first isolator diaphragm disposed proximate the first process fluid inlet and operably coupled to the first sensor inlet through a first fill fluid volume;

a second isolator diaphragm disposed proximate the second process fluid inlet and operably coupled to the second sensor inlet through a second fill fluid volume;

transmitter circuitry operably coupled to the first and second pressure sensors and configured to measure an electrical parameter of the sensors and provide an indication of differential pressure; and

a third fluid volume substantially surrounding the first and second pressure sensors, the third fluid volume exerting a compressive force on the first and second pressure sensors.