Pressure monitor incorporating saw device

• US 6,865,950 B2
• Filed: 10/10/2001
• Issued: 03/15/2005
• Est. Priority Date: 10/10/2000
• Status: Expired due to Term

• Current Assignee: Transense Technologies Plc
• Original Assignee: Transense Technologies Plc
• Inventors: Freakes, Graham Michael, Beckley, Peter John, Leigh, Arthur John, Vile, David Daniel George, Kalinin, Victor Alexandrovich
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): JENKINS, JERMAINE L
• Application Number:
  US10/398,083
• Publication Number:
  US 20040020299A1
• Time in Patent Office: 1,252 Days
• Field of Search: 73700-756
• US Class Current: 73/702
• CPC Class Codes: G01L 9/0025 with acoustic surface waves

Abstract

A pressure monitoring device includes a rigid base (2) which has secured thereto a lid (5) to define a hermetically sealed chamber (6). The lid (5) is of flexible metal material and the major surface (5A) of the lid forms a diaphragm which will deflect in response to changes in the pressure surrounding the device. A substrate (7) upon which a plurality of SAW devices are laid down is supported on a rigid frame (3A) of the base so that the central region thereof is unsupported between edges (11, 12). A dimple (10) is formed in the lid (5) and presses on a central region of the substrate (7). Changes in pressure will accordingly cause distortion of the central region of the substrate. The end regions (8, 9) of the substrate (7) carry further SAW devices so that, by analyzing the changes in characteristics of all the SAW devices a temperature compensated indication of pressure change, together with an indication of absolute temperature, may be provided by interrogating the SAW devices. The base (2) and the lid (5) are preferably both of metal alloy and may be secured together by soldering. Antennae associated with the SAW devices may be laid down as tracks on the surface of the base (2).

Claims

1. A pressure monitor comprising a base having a rigid frame;

a lid secured to the base to define with the base a substantially fluid tight chamber, at least part of the lid being flexible and forming a diaphragm which will deflect in response to changes in the fluid pressure surrounding the monitor, at least one surface acoustic wave (SAW) device supported within the chamber;

an means remote from the edge of the frame for transmitting movement of the diaphragm to the SAW device whereby movement of the diaphragm induced by a change in pressure in a zone surrounding the monitor will result in distortion of the SAW device; and

the SAW device comprising surface elements laid down on a substrate, the substrate having, in addition to the zone thereof which is subject to distortion by movement of the diaphragm, at least one other region which is not subject to substantial distortion as a result of movement of the diaphragm, and upon which at least one further set of surface elements are laid down to form at least one further SAW device to provide temperature compensation to the output of the monitor.

2. A pressure monitor according to claim 1 wherein three SAW devices are provided whereby the monitor provides a temperature compensated indication of pressure changes, together with an indication of the temperature of the monitor.

3. A pressure monitor according to claim 1 wherein the means for transmitting movement of the diaphragm to the SAW device comprises a projection extending from a major surface of the lid.

4. A pressure monitor according to claim 3 wherein the projection is formed by deforming material of the lid.

5. A pressure monitor according to claim 1 wherein at least one antenna for providing radio communication to the SAW device is laid down on a surface of the base.

6. A pressure monitor according to claim 1 wherein the lid is of a metal or metal alloy and is secured to the base by soldering.

7. A pressure monitor according to claim 1 wherein the chamber is hermetically sealed and includes a gas at a pre-determined absolute pressure.

8. A pressure monitor according to claim 1 including a plurality of SAW devices provided on a plurality of substrates, at least one of the substrates being secured to the base in a manner which is not the subject to distortion as a result of movement of the diaphragm.

9. A pressure monitor according to claim 1 wherein the substrate of the at least one SAW device is secured to the base by means of a flexible adhesive.

10. A pressure monitor comprising a base having a rigid frame;

a lid acting as a diaphragm secured to the rigid frame to define with the base a substantially fluid tight chamber, the diaphragm having at least one indentation formed therein to define at least one ridge projecting into the chamber; and

at least one SAW device mounted within the chamber and secured to the ridge, wherein the at least one SAW device includes three SAW devices whereby the monitor provides a temperature compensated indication of pressure changes, together with an indication of the temperature of the monitor.

11. A pressure monitor according to claim 10 comprising a substantially fluid tight chamber having a lid forming a diaphragm which deflects in response to changes in the fluid pressure surrounding the monitor;

the at least one surface acoustic wave (SAW) device supported within the chamber; and

means for transmitting movement of the diaphragm to the at least one SAW device whereby movement of the diaphragm induced by a change in pressure in a zone surrounding the monitor results in distortion of the at least one SAW device.

12. A pressure monitor according to claim 10 wherein the at least one SAW device comprises surface elements laid down on a substrate, the substrate having at least one region which is not subject to substantial distortion as a result of movement of the diaphragm, and upon which at least one further set of surface elements are laid down to form at least one of the SAW devices to provide temperature compensation to the output of the monitor.

13. A pressure monitor according to claim 12, wherein the plurality of SAW devices are provided on a plurality of substrates and includes at least one of the substrates being secured in a manner which is not the subject to distortion as a result of movement of the diaphragm.

14. A pressure monitor according to claim 12 wherein the substrate of the at least one SAW device is secured to the base by means of a flexible adhesive.

15. A pressure monitor according to claim 11 wherein the means for transmitting movement of the diaphragm to the at least one SAW device comprises a projection extending from a major surface of the lid.

16. A pressure monitor according to claim 15 wherein the projection is formed by deforming material of the lid.

17. A pressure monitor according to claim 10 wherein the lid is of a metal or metal alloy and is secured to the base by soldering.

18. A pressure monitor according to claim 10 wherein the chamber is hermetically sealed and includes a gas at a pre-determined absolute pressure.

19. A pressure monitor comprising:

a base having a rigid frame;

a lid secured to the base to define with the base a substantially fluid tight chamber, at least part of the lid being flexible and forming a diaphragm which will deflect in response to changes in the fluid pressure surrounding the monitor;

a plurality of surface acoustic wave (SAW) devices provided on a plurality of substrates supported within the chamber;

means remote from the edge of the frame for transmitting movement of the diaphragm to the SAW device whereby movement of the diaphragm induced by a change in pressure in a zone surrounding the monitor will result in distortion of at least one the SAW devices; and

at least one of the substrates being secured to the base in a manner which is not the subject to distortion as a result of movement of the diaphragm.