Registers – Platform operated – Platform actuated traffic counters
Patent
1975-01-23
1976-11-02
Boudreau, Leo H.
Registers
Platform operated
Platform actuated traffic counters
324 78D, 324186, 340 38L, 3401463K, G01R 2306, G08G 101
Patent
active
039899322
ABSTRACT:
Apparatus for use in combination with an inductive loop for detecting metal objects, e.g. vehicles, in the immediate vicinity of said loop. The loop may, for example, be a coil of wire buried in a roadway in a plane parallel to the roadway surface. Oscillator circuitry is operatively connected to the loop with the frequency of oscillation being determined by the loop inductance, which in turn is dependent on whether or not the vehicle is over the loop. The loop frequency is monitored by digital circuitry including a loop counter which counts loop oscillator cycles and a duration counter which measures the time duration of a fixed number of loop oscillator cycles. The measured time duration is compared with an adaptable reference duration to ascertain whether the loop oscillator frequency has increased or decreased. The presence of a vehicle over the loop decreases loop inductance, increases loop frequency, and thus reduces the measured time duration of a fixed number of loop cycles. A reduction in the measured time duration by an amount greater than a preselected threshold value produces an output signal or "call" to indicate the vehicle's presence.
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patent: 3420988 (1969-01-01), Hunt et al.
patent: 3559066 (1971-01-01), Pincus
patent: 3631343 (1971-12-01), Schmidhauser
patent: 3665382 (1972-05-01), Siklos
patent: 3708750 (1973-01-01), Bucks et al.
patent: 3820100 (1974-06-01), Ballinger et al.
patent: 3868626 (1975-02-01), Masher
patent: 3873964 (1975-03-01), Potter
patent: 3875555 (1975-04-01), Potter
Boudreau Leo H.
Canoga Controls Corporation
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