Magnetically driven vibrating beam force transducer
First Claim
1. In a vibrating beam force transducer, of the type comprising first and second beams having respective first and second longitudinal axes that are parallel to one another and drive means electrically coupled to the beams for causing the beams to oscillate at a resonant frequency that is a function of a force applied along the longitudinal axes, the improvement wherein the drive means provides an electrical current to the beams, and wherein the transducer comprises conduction means physically coupled to the beams for receiving the electrical current and conducting the electrical current along a current path that includes first and second axial components parallel to the first and second longitudinal axes, the first axial component being opposite in direction to the second axial component, and magnetic means for creating a magnetic field that intersects said axial components, whereby the electrical current flowing along said current path interacts with the magnetic field so as to produce forces on the beams that cause the beams to oscillate at said resonant frequency.
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Abstract
A vibrating beam force transducer that can be realized in a silicon micromachined device such as a micromachined accelerometer. The transducer includes a beam having a longitudinal axis, and a drive circuit electrically coupled to the beam for causing the beam to oscillate at a resonant frequency that is a function of a force applied along the longitudinal beam axis. The drive circuit provides an electrical current to the beam, and the beam, or a conductive portion thereof, conducts the current along a path that includes an axial component parallel to the longitudinal axis. A magnetic field is created intersecting the axial component, such that the electric current interacts with the magnetic field to produce a force that causes the beam to oscillate at the resonant frequency. In a preferred embodiment, the transducer has a double ended tuning fork configuration, and the current path extends along one beam and back along the other beam.
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Citations
11 Claims
- 1. In a vibrating beam force transducer, of the type comprising first and second beams having respective first and second longitudinal axes that are parallel to one another and drive means electrically coupled to the beams for causing the beams to oscillate at a resonant frequency that is a function of a force applied along the longitudinal axes, the improvement wherein the drive means provides an electrical current to the beams, and wherein the transducer comprises conduction means physically coupled to the beams for receiving the electrical current and conducting the electrical current along a current path that includes first and second axial components parallel to the first and second longitudinal axes, the first axial component being opposite in direction to the second axial component, and magnetic means for creating a magnetic field that intersects said axial components, whereby the electrical current flowing along said current path interacts with the magnetic field so as to produce forces on the beams that cause the beams to oscillate at said resonant frequency.
- 6. In a vibrating beam force transducer, of the type comprising a beam having a longitudinal axis and drive means electrically coupled to the beam for causing the beam to oscillate at a resonant frequency that is a function of a force applied along the longitudinal axis, the improvement wherein the drive means provides an electrical current to the beam, and wherein the transducer comprises conduction means physically coupled to the beam for receiving the electrical current and conducting the electrical current along a current path that includes a first axial component extending in a first longitudinal direction parallel to the longitudinal axis and spaced from the longitudinal axis in a first transverse direction normal to the longitudinal axis, and a second axial component extending in a second longitudinal direction parallel to the longitudinal axis and spaced from the longitudinal axis in a second transverse direction parallel to the first transverse direction, the first and second longitudinal directions being opposite to one another, and the first and second transverse directions being opposite to one another, and magnetic means for creating a magnetic field that intersects said axial components, whereby the electric current flowing along the current path interacts with the magnetic field so as to produce a torque on the beam that causes the beam to oscillate torsionally at said resonant frequency.
- 10. In a vibrating beam force transducer, of the type comprising a body having a double-ended tuning fork construction, the body including first and second beams that are mutually parallel to one another, the first and second beams extending between first and second mounting pads, the beams having respective first and second longitudinal axes that are parallel to one another, the transducer further comprising drive means electrically coupled to the beams for causing the beams to oscillate at a resonant frequency that is a function of a force applied along the longitudinal axes, the improvement wherein the drive means provides an electrical current to the beams, and wherein the transducer comprises conduction means physically coupled to the beams for receiving the electrical current and conducting the electrical current along a current path that includes first and second axial components parallel to the first and second longitudinal axes, and magnetic means for creating a magnetic field that intersects said axial components, whereby the electrical current flowing along said current path interacts with the magnetic field so as to produce forces on the beams that cause the beams to oscillate at said resonant frequence, the current path extending from the first mounting pad along the first beam to the second mounting pad, and then along the second beam back to the first mounting pad.
Specification