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Compensation for Nonlinear Variation of Gap Capacitance with Displacement

  • US 20160209984A1
  • Filed: 09/28/2013
  • Published: 07/21/2016
  • Est. Priority Date: 09/28/2013
  • Status: Active Grant
First Claim
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1. A capacitive force sensor characterization system for calibrating a capacitive force sensor included in a personal electronic device, the capacitive force sensor including a first capacitor plate coupled to a flexible element of the personal electronic device and a second capacitor plate coupled to an internal structural member of the personal electronic device, the flexible element being coupled to a housing of the personal electronic device and the internal structural member not being coupled to the housing during characterization, the capacitive force sensor characterization system comprising:

  • a housing fixture adapted to hold the housing of the personal electronic device;

    a member fixture adapted to hold the internal structural member of the personal electronic device;

    a positioner coupled to at least one of the housing fixture or the member fixture, the positioner adapted to vary a gap width between the first capacitor plate and the second capacitor plate in response to a drive signal;

    a position sensor adapted to measure differences in the gap width between the first capacitor plate and the second capacitor plate relative to an initial gap width;

    control circuitry electrically coupled to the positioner to provide the drive signal to the positioner, the control circuitry adapted to generate the drive signal following a test procedure such that, in response to the drive signal, the positioner varies the gap width between the first capacitor plate and the second capacitor plate from the initial gap width to at least two test gap widths; and

    a processor electrically coupled to the first capacitor plate, the second capacitor plate, and the position sensor, the processor adapted to determine;

    a capacitive sensor gain;

    a capacitive sensor offset; and

    an initial effective separation between the first capacitor plate and the second capacitor plate.

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