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Capacitance sensor

  • US 7,944,216 B2
  • Filed: 12/05/2008
  • Issued: 05/17/2011
  • Est. Priority Date: 12/06/2007
  • Status: Expired due to Fees
First Claim
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1. A capacitance sensor, comprising:

  • a first electrode and a second electrode;

    a frequency spread signal generation circuit coupled to the first electrode and the second electrode to apply a first frequency spread signal based on a first spread sequence and a periodic signal with a frequency to the first electrode, and concurrently a second frequency spread signal based on a second spread sequence being orthogonal to the first spread sequence and the periodic signal to the second electrode;

    a frequency controller coupled to the frequency spread signal generation circuit to vary the frequency of the periodic signal;

    a receiver circuit coupled to the first electrode and the second electrode or a further electrode to receive a version of the first frequency spread signal which depends on a capacitance applied to the first electrode and a version of the second frequency spread signal that depends on a capacitance applied to the second electrode; and

    an evaluation circuit coupled to the receiver circuit to determine a capacitance value based on the received dependent versions of the first and second frequency spread signal.

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