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System and method for interrogating a capacitive sensor

  • US 6,469,524 B1
  • Filed: 08/25/2000
  • Issued: 10/22/2002
  • Est. Priority Date: 08/25/2000
  • Status: Expired due to Fees
First Claim
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1. A sensing circuit for use with a proximity sensor having a first electrode and a second electrode and a capacitance between the first electrode and second electrode, the sensing circuit comprising:

  • a signal generator for generating an alternating signal, said signal generator for connection to the first electrode of the sensor;

    a synchronous detector having a first input and a second input, said first input for connection to the second electrode of the sensor; and

    a phase shifter coupled to said signal generator, said phase shifter generating a phase shifted signal in response to said alternating signal, said phase shifted signal being provided to said second input of said synchronous detector;

    wherein said synchronous detector detects a change in the capacitance between the first electrode and the second electrode in response to a signal from the second electrode and the phase shifted signal.

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