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Environmental tracking in inductance loop vehicle detection systems

  • US 4,862,162 A
  • Filed: 07/30/1987
  • Issued: 08/29/1989
  • Est. Priority Date: 12/02/1982
  • Status: Expired due to Fees
First Claim
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1. In a vehicle presence detection system in which an inductive sensor loop is an element of a tuned circuit in a loop oscillator, a method of discriminating against parameter variations due to environmental changes during the presence of a vehicle, comprising the steps of repeatedly comparing a variable sample number that is a function of the oscillator inductance with a reference number for providing an indication of the arrival or departure of a vehicle, and repeatedly updating the reference number in accordance with detected environmental changes at predetermined rail time intervals dependent of an operational frequency of the system.

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