RESONATOR-BASED MAGNETIC FIELD SENSOR

• US 20090015250A1
• Filed: 08/22/2005
• Published: 01/15/2009
• Est. Priority Date: 08/24/2004
• Status: Active Grant

• Current Assignee: Sensirion AG (Sensirion Holding AG)
• Original Assignee: Sensirion AG (Sensirion Holding AG)
• Inventors: Sunier, Robert, Brand, Oliver, Vancura, Tobias A.
• Granted Patent: US 7,696,749 B2
• Time in Patent Office: Days
• US Class Current: 324/244
• CPC Class Codes: G01R 33/028 Electrodynamic magnetometers

Abstract

The resonator-based magnetic field sensor system has an oscillatory member as resonator, means for driving an electrical current through said resonator such that its resonance frequency is altered by an external magnetic field to be measured (measurand), and means for detecting or measuring said altered resonance frequency. A secondary excitation of the resonator is effected to determine the said altered resonance frequency from which the measurand can be deduced. In the preferred embodiment, the secondary excitation is included in a closed loop, thus creating an oscillator vibrating at the altered resonance frequency. Though it is known to use the oscillation amplitude of a suitable resonator for this purpose, the novel sensor system identifies and/or measures the frequency (not the amplitude) of the oscillation, which is a function of the magnetic field to be measured.

Claims

1. A resonator-based magnetic field sensor system comprising:

an oscillatory member as resonator,

means for driving an electrical, preferably alternating, current through said resonator such that its resonance frequency is altered by an external magnetic field to be measured (measurand),

means for detecting or measuring said resonance frequency when altered by said measurand.

2. The sensor system according to claim 1, wherein

the detection means includes means for generating a secondary excitation of the resonator, said secondary excitation being generated either in open or closed loop.

3. The sensor system according to claim 2, wherein the secondary excitation is independent of any magnetic-field-based actuators.

4. The sensor system according to any of the claim 1, further comprising

sensing means for converting the movement of the resonator into an electrical signal by providing an output which is a function of the movement of said resonator, said movement being the position, and/or speed, and/or acceleration of the resonator.

5. The sensor system according to claim 1, wherein

the current driving means generates an electrical current through the resonator, said current being an alternating current (AC) and being a function of the movement of said resonator, said movement being the position, and/or speed, and/or acceleration of the resonator.

6. The sensor system according to claim 1, wherein

the detection means includes means for determining the transfer function, and/or searching for the maximum amplitude, and/or the maximum phase drop of the measurand-altered resonator.

7. The sensor system according to claim 2, wherein

the means for secondary excitation is part of a closed-loop structure, said closed-loop structure being able to sustain a self-oscillation and wherein the measurand-altered resonator is the frequency-determining element.

8. The sensor system according to claim 2, wherein

the frequency of the secondary excitation is a function the movement of the resonator.

9. The sensor system according to claim 1, further including

means for calibrating said sensor system by switching-off the electrical current through the resonator, said calibrating means being activatable once, periodically, or continuously.

10. An arrangement of a plurality of sensor systems according to claim 1 for detecting and/or measuring two or more components of a magnetic field.

11. A method comprising using a sensor system according to claim 1 for detecting and/or measuring the magnetic field of the earth.

12. A method of making a sensor system according to any claim 1, including using MEM technology and/or CMOS integration technology.