Communications: electrical – Vehicle detectors – Environmental or drift compensation
Patent
1991-06-17
1994-11-01
Kuntz, Curtis
Communications: electrical
Vehicle detectors
Environmental or drift compensation
340941, G08G 101
Patent
active
053610644
ABSTRACT:
A vehicle detector includes an inductive sensor which is driven by an oscillator to produce an oscillator signal having a frequency which is a function of inductance of the inductive sensor. Presence of a vehicle is detected when measured frequency of the oscillator signal changes by more than a threshold value. The effects of magnetic flux produced by adjacent power lines are compensated by measuring the frequency of the oscillator signal during a plurality of sample periods and characterizing the fluctuation of the measured frequency as a function of phase of a power main signal. During a normal measurement period, the frequency of the oscillator signal is measured, and the phase of the power main signal during the measurement period is determined. An output signal is produced based upon the measured frequency, the phase, and the known fluctuation of measured frequency as a function of phase of the power main signal.
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Hamer Steven M.
Hoekman Earl B.
Bartingale Kari H.
Griswold Gary L.
Kirn Walter N.
Kuntz Curtis
Lee Ping W.
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