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Microaccelerometer employing resonant circuit detection of seismic mass displacement

  • US 5,801,309 A
  • Filed: 11/30/1995
  • Issued: 09/01/1998
  • Est. Priority Date: 03/18/1994
  • Status: Expired due to Fees
First Claim
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1. An accelerometer comprising:

  • a seismic mass having upper and lower surfaces;

    a support wafer positioned below said lower surface of said seismic mass and having an upper surface separated from and opposed to the lower surface of said seismic mass;

    a cover wafer positioned above said upper surface of said seismic mass and having a lower surface separated from and opposed to the upper surface of said seismic mass;

    beam means for flexibly mounting said seismic mass between said support wafer and said cover wafer;

    a first oscillator having a resonant circuit, including inductance and first capacitance, said first capacitance comprising a dielectric positioned between a conductive plate arrangement covering a substantial area of said upper surface of said seismic mass and a conductive plate arrangement on said lower surface of said cover wafer;

    a second oscillator having a resonant circuit including inductance and second capacitance, said second capacitance comprising a dielectric positioned between a conductive plate arrangement covering a substantial area of said lower surface of said seismic mass and a conductive plate arrangement on said upper surface of said support wafer; and

    frequency difference means coupled to said first oscillator and said second oscillator for providing an output indicative of a difference in oscillation frequencies of said first and second oscillators when said accelerometer is subjected to an acceleration event that positionally displaces said seismic mass, said output of the difference in oscillation frequencies being a measure of said acceleration event.

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