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Diagnostic capacitive occupancy or proximity detector

  • US 9,764,668 B2
  • Filed: 11/12/2013
  • Issued: 09/19/2017
  • Est. Priority Date: 11/22/2012
  • Status: Active Grant
First Claim
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1. A capacitive occupancy or proximity detector, comprisinga heating circuit, including a heating element connected between a first and a second node, said first and second nodes configured to connect said heating circuit to a heating current source;

  • an impedance measurement circuit connected to said heating element configured to measure impedance between said heating element and a node at ground potential; and

    a diagnostic circuit configured to measure electrical resistance across said heating circuit between said first and second nodes, said diagnostic circuit includinga heating current sensor arranged in said heating circuit, configured to sense a heating current across said heating circuit;

    a current supply device connected to one of said first and second nodes configured to drive a diagnostic current across said heating circuit; and

    a current limiting ground path connected to the other of said first and second nodes, configured to drain said diagnostic current and to block said heating current.

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