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Omnidirectional accelerometer device and medical device incorporating same

  • US 8,386,042 B2
  • Filed: 11/03/2009
  • Issued: 02/26/2013
  • Est. Priority Date: 11/03/2009
  • Status: Active Grant
First Claim
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1. An omnidirectional accelerometer device comprising:

  • a piezoelectric sensor element comprising an electrically conductive support substrate, a layer of piezoelectric material overlying the support substrate, and a plurality of electrically conductive sensor electrodes overlying the piezoelectric material, the piezoelectric sensor element further comprising a mass-supporting platform and a plurality of mass-supporting arms, each of the sensor electrodes being located on a corresponding one of the mass-supporting arms;

    a proof mass coupled to the mass-supporting platform by a connecting rod that holds the proof mass above a surface of the piezoelectric sensor element at a specified height;

    an electromechanical mounting arrangement configured to mechanically and electrically couple the piezoelectric sensor element to a circuit board such that each of the sensor electrodes is electrically coupled to a respective contact pad of the circuit board;

    an electrically conductive offset block that mechanically and electrically couples the support substrate of the piezoelectric sensor element to a ground contact pad of the circuit board; and

    a signal processing module coupled to the sensor electrodes, the signal processing module being configured to process sensor signals generated in response to deflection of the piezoelectric sensor element caused by the proof mass, the signal processing module comprising a first signal processing sub-module configured to process the sensor signals for human activity monitoring, and a second signal processing sub-module configured to process the sensor signals for impact detection;

    wherein;

    the first signal processing sub-module and the second signal processing sub-module are coupled in parallel to the sensor electrodes to enable concurrent processing of the sensor signals;

    the first signal processing sub-module comprises a sensor signal input element, an amplifier-rectifier coupled to an output of the sensor signal input element, a high pass filter coupled to an output of the amplifier-rectifier, a voltage limiter coupled to an output of the high pass filter and an integrator coupled to an output of the voltage limiter; and

    the second signal processing sub-module comprises the sensor signal input element, the amplifier-rectifier, and a peak and hold circuit coupled to an output of the amplifier-rectifier.

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