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Capacitive occupancy detector apparatus

  • US 4,796,013 A
  • Filed: 10/15/1986
  • Issued: 01/03/1989
  • Est. Priority Date: 10/18/1985
  • Status: Expired due to Term
First Claim
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1. A personnel detector comprisingpersonnel containment meansfirst and second electrodes insulated from each other and arranged such that at least part of a person present in said personnel containment means is disposed therebetween;

  • capacitance detecting means for detecting a capacitance between the first and the second electrodes and providing a representative electrical signal;

    processing means including storage means for storing the electrical signal;

    storage update means for causing the electrical signal stored in the storage means to be updated at given time intervals;

    comparison means for producing an electrical signal representing the arrival of a person whenever a difference between the electrical signal developed by the capacitance detecting means and the signal stored by the storage means exceeds a first threshold value; and

    means for setting a second threshold value based on the capacitance detected during the presence of a person and determining the departure of a person when the capacitance detected by the detecting means decreases below said second threshold value;

    wherein said capacitance detecting means includes an oscillator means which produces a signal of a frequency which decreases with an increasing capacitance and a frequency/voltage converter.

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