DEVICE FOR MEASURING PRESSURE, VARIATION IN ACOUSTIC PRESSURE, A MAGNETIC FIELD, ACCELERATION, VIBRATION, OR THE COMPOSITION OF A GAS

• US 20100275675A1
• Filed: 12/04/2008
• Published: 11/04/2010
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: Valtion Teknillinen Tutkimuskeskus
• Original Assignee: Valtion Teknillinen Tutkimuskeskus
• Inventors: Seppa, Heikki, Sillanpää, Teuvo
• Granted Patent: US 8,850,893 B2
• Time in Patent Office: Days
• US Class Current: 73/24.01
• CPC Class Codes: G01L 11/06 Ultrasonic means
• CPC Class Codes: G01L 9/0041 Transmitting or indicating the displacement of flexible diaphragms
• CPC Class Codes: G01N 2291/0215 Mixtures of three or more gases, e.g. air
• CPC Class Codes: G01N 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: G01R 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B

Abstract

The invention relates to a sensor (1) and a method for measuring pressure, variation in sound pressure, a magnetic field, acceleration, vibration, or the composition of a gas. The sensor (1) comprises an ultrasound transmitter (2), and a cavity (4) arranged in connection with it. According to the invention, the sensor (1) comprises a passive sensor element (3, 3′) located at the opposite end of the cavity (4) to the ultrasound transmitter (2), the distance of which from the ultrasound transmitter (2) is selected in such a way that the resonance condition is met at the ultrasound frequency used, the ultrasound transmitter (2) comprises a light-construction diaphragm oscillator (9), which is thus well connected to the surrounding medium, and the sensor includes means for measuring the interaction between the ultrasound transmitter (2) and the cavity (4).

Claims

1. Sensor (1) for measuring pressure, variation in sound pressure, a magnetic field, acceleration, vibration, or the composition of a gas, which sensor (1) comprises

an ultrasound transmitter (2), and

a cavity (4) arranged in connection with this, which is in resonance mode at the ultrasound frequency used,

characterized in that

the sensor (1) comprises a passive sensor element (3, 3′

), the distance of which from the ultrasound transmitter (2) is selected in such a way that the resonance condition is met, located at the opposite end of the cavity (4) to the ultrasound transmitter (2),

the ultrasound transmitter (2) comprises a light-construction diaphragm oscillator (9), which is thus well connected to the surrounding medium, and

the sensor contains means for measuring the interaction between the ultrasound transmitter (2) and the cavity (4).

2. Sensor (1) according to claim 1, characterized in that the measuring means for the interaction between the ultrasound transmitter (2) and the cavity (4) are power-measurement means.

3. Sensor (1) according to claim 1 or 2, characterized in that the construction is formed using MEMS technology, in such a way that there is a high underpressure inside the ultrasound transmitter (2).

4. Sensor (1) according to claim 1, characterized in that the sensor is a surface micromechanical structure formed on an SOI disc.

5. Sensor (1) according to claim 1, characterized in that, in the basic state, the distance between the ultrasound transmitter (2) and the sensor element (3, 3′

) is one quarter, one half, or a multiple of these, of the wavelength of the ultrasound frequency used.

6. Sensor (1) according to claim 1, characterized in that the sensor element (3, 3′

) is on the outer surface of a device case, such as the device case of a mobile telephone or watch.

7. Sensor (1) according to claim 6, characterized in that the outer surface of the device case of the device, such as a mobile telephone or watch, connected to the sensor, forms at least part of the sensor (1).

8. Sensor (1) according to claim 1, characterized in that the cavity (4) is connected to the environment by means of a gas-permeable structure, in order to permit the measurement of gas content.

9. Sensor (1) according to claim 1, characterized in that an additional mass (32) is located in the cavity (4), for the measurement of acceleration.

10. Sensor (1) according to claim 1, characterized in that a current-transporting coil is located in the passive diaphragm (3), for the measurement of a magnetic field.

11. Sensor (1) according to claim 1, characterized in that a reflector cavity (6) is arranged on top of the cavity (4), in order to increase the sensitivity of the sensor.

23. Use of the sensor according to claim 1 for measuring a gas content.

24. Use of the sensor according to claim 1 for measuring a magnetic field.

25. Use of the sensor according to claim 1 for measuring pressure.

26. Use of the sensor according to claim 1 for measuring distance.

27. Use of the sensor according to claim 1 as a microphone.

28. Use of the sensor according to claim 1 for measuring acceleration.

12. Method (1) for measuring pressure, variation in sound pressure, a magnetic field, acceleration, vibration, or the composition of a gas, in which method

an ultrasound transmitter (2) is used to create ultrasound in a cavity (4), which is in resonance mode at the ultrasound frequency used,

characterized in that

a passive sensor element (3, 3′

), the distance of which from the ultrasound transmitter (2) is selected in such a way that the resonance condition is met, is located at the opposite end of the cavity to the ultrasound transmitter (2),

a construction, in which there is a light-construction diaphragm oscillator (9), which is thus well connected to the surrounding medium, is used as the ultrasound transmitter (2), and

the interaction between the ultrasound transmitter (2) and the cavity (4) is used to determine the desired variable.

13. Method according to claim 12, characterized in that the interaction between the ultrasound transmitter (2) and the cavity (4) is implemented by measuring the power drawn by the ultrasound transmitter (2).

14. Method according to claim 12 or 13, characterized in that the construction is formed using MEMS technology, in such a way that there is a high underpressure inside the ultrasound transmitter (2).

15. Method according to claim 12, characterized in the construction is formed on an SOI disc.

16. Method according to claim 12, characterized in that, in the basic state, one quarter, one half, or a multiple of these of the wavelength of the ultrasound frequency is used as the distance between the ultrasound transmitter (2) and the sensor element (3, 3′

).

17. Method according to claim 12, characterized in that the sensor element (3, 3′

) is located on the outer surface of a device case, such as a mobile telephone, so that it can be used as part of the interface.

18. Method according to claim 17, characterized in that the outer surface of the device case of the device, such as a mobile telephone or watch, connected to the sensor, is used as at least part of the sensor (1).

19. Method according to claim 12, characterized in that the cavity (4) is connected to the environment by means of a structure permeable to the gas being measured, in order to permit measurement of the gas content.

20. Method according to claim 12, characterized in that an additional mass (32), for measuring acceleration, is located in the cavity (4).

21. Method according to claim 12, characterized in that a coil transporting current is located in the passive diaphragm (3), in order to measure a magnetic field.

22. Method according to claim 12, characterized in that a reflector cavity (6) is arranged on top of the cavity (4), in order to increase the sensitivity of the sensor.

29. Device for measuring pressure, the variation of sound pressure, a magnetic field, acceleration, vibration, or the composition of a gas, which is performed as a measurement of the real and imaginary parts of a 300 ′

Ω

-10 k-′

Ω

impedance, characterized in that measurement based on micromechanical ultrasound and a micro-cavity is used in the measurement.

30. Device according to claim 29, characterized in that an integrated MEMS construction is used in the measurement.

31. Device according to claim 29 or 30, characterized in that the measurement sensor is based on a silicon-based ultrasound sensor and the wavelength, a quarter of the wavelength, or multiples of these of ultrasound set on top of it.

32. Device according to claim 29, characterized in that the impedance of the ultrasound is measured and compared to the deviation of the cavity above it from the aforementioned length.

33. Device according to claim 29, characterized in that, in the series resonance of the ultrasound, the impedance of the transmitter to small changes is directly proportional to the height of the cavity and the width of the resonance is proportional to the damping of the air in the cavity.