Acceleration Insensitive Pressure Sensor

• US 20080178666A1
• Filed: 06/25/2007
• Published: 07/31/2008
• Est. Priority Date: 10/18/2004
• Status: Active Grant

• Current Assignee: Precision Mechatronics Pty Ltd
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia, Mallinson, Samuel George
• Granted Patent: US 7,770,441 B2
• Time in Patent Office: Days
• US Class Current: 73/146.3
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: G01L 15/00 Devices or apparatus for measuring two or more fluid pressure values simultaneously
• CPC Class Codes: G01L 19/0636 using particle filters
• CPC Class Codes: G01L 9/0047 Diaphragm with non uniform thickness, e.g. with grooves, bosses or continuously varying thickness
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

A pressure sensor for sensing a fluid pressure in a high acceleration environment. The sensor has a non-planar membrane between fluid at a reference pressure and fluid at the pressure to be sensed, such that the non-planar membrane deflects due to pressure differentials between the reference pressure and the fluid pressure. The deflection is converted into an output signal indicative of the fluid pressure by associated circuitry. By keeping the area of the membrane exposed to the fluid in the chamber to less than 0.1 grams, the acceleration forces have minimal affect on the amount that membrane flexes.

Claims

1. A pressure sensor for sensing a fluid pressure, the pressure sensor comprising:

a non-planar membrane between fluid at a reference pressure and fluid at the pressure to be sensed, such that the non-planar membrane deflects due to pressure differentials between the reference pressure and the fluid pressure; and

,

associated circuitry for converting the deflection of the non-planar membrane into an output signal indicative of the fluid pressure;

wherein,

the membrane area exposed to the fluid at the reference pressure has a mass of less than 0.1 grams.

2. A pressure sensor according to claim 1 wherein the membrane is corrugated.

3. A pressure sensor according to claim 2 wherein, the membrane corrugations have a period of between 5 microns and 15 microns.

4. A pressure sensor according to claim 2 wherein, the membrane is substantially circular and the corrugations are annular.

5. A pressure sensor according to claim 1 wherein the corrugations have a substantially square-shaped cross-sectional profile.

6. A pressure sensor according to claim 5 further comprising an apertured guard over the membrane formed using lithographically masked etching and deposition techniques.

7. A pressure sensor according to claim 1 wherein, the chamber, the flexible membrane and the associated circuitry are formed on a silicon wafer substrate using lithographically masked etching and deposition techniques.

8. A pressure sensor according to claim 1 wherein the pressure sensor is adapted to sense the air pressure within a pneumatic tire.

9. A pressure sensor according to claim 1 wherein the sensor is a capacitative sensor having:

a conductive layer deposited in the chamber to form a first capacitor electrode; and

,

the flexible membrane is conductive in order to form a second capacitor electrode;

such that,

deflection of the flexible membrane changes the capacitance which the associated circuitry converts to the output signal.

10. A pressure sensor according to claim 9 further comprising a CMOS layer disposed between the conductive layer and the substrate.

11. A pressure sensor according to claim 10 further comprising a passivation layer at least partially deposited over the conductive layer.

12. A pressure sensor according to claim 1 wherein, the membrane is approximately 0.5 μ

m thick.

13. A pressure sensor according to claim 9 wherein the conductive layer is less than 50 microns from the membrane in its undeflected state.

14. A pressure sensor according to claim 1 wherein the membrane is circular with a diameter less than 500 microns.

15. A pressure sensor according to claim 1 wherein the sensor is powered by radio waves transmitted from a remote source.

16. A pressure sensor according to claim 1 wherein the membrane is a laminate having at least two layers wherein at least one of the layers is at least partially formed from conductive material.

17. A pressure sensor according to claim 16 wherein the layers within the laminate are be formed from the deposition of different metal ceramics.

18. A pressure sensor according to claim 17 wherein the metal ceramics are metal nitrides or mixed metal nitrides.

19. A pressure sensor according to claim 1 further comprising a second chamber with a second membrane, the second chamber being sealed from the fluid pressure and the second membrane deflecting from a predetermined pressure difference in the second chamber;

wherein,

the associated circuitry converts the deflection of the second membrane into an adjustment of the output signal to compensate for the temperature of the sensor.

20. A pressure sensor according to claim 19 wherein the sensor is a capacitative sensor, with a conductive layer deposited in each of the first and second chambers and the first and second flexible membranes are conductive;

such that,

the conductive layer in the first chamber and the first flexible membrane form capacitor electrodes and the deflection of the first flexible membrane changes the capacitance which the associated circuitry converts to the output signal.