Abstract: An apparatus for sensing variations in an inductive field, or inductive sensor. The inductive sensor is adapted for detecting the lateral offset of a vehicle within a roadway, especially those with multiple traffic lanes, without regard to lane boundaries, which may vary. Lateral offset information is necessary for determining lane usage statistics and is useful in detecting unsafe driving behaviors evidenced by erratic variations in lane position. Such unsafe driving behaviors are indicative of, for example, intoxicated or drowsy drivers, obstacles in the roadway requiring drastic avoidance measures, aggressive driving and other generally unsafe roadway conditions. In addition, lane position information can be passed back to the vehicle to allow for automated lane-keeping or passed to other detectors for self-calibration of the system.

Abstract: A wire-loop vehicle detector is configured with a vertically oriented blade aligned at an angle to the direction of traffic-flow with each end of the blade extending laterally beyond the normal limits of vehicle presence over the blade. The extended blade configuration of the wire-loop constrains over-passing vehicles to present repeatable inductive signatures while electromagnetic noise and thermal-drift are selectively canceled using a secondary coil to increase the signal-to-noise ratio of inductance measurements. Inductive signatures of vehicles are recorded using a high-speed and high-precision method of making multiple successive measurements of the inductance of a wire-loop as vehicles pass over. Inductive signatures of automotive vehicles are useful for parking-lot revenue control, car-bomb detection, passive security of isolated communities, and other traffic-flow monitoring and control applications.

Abstract: An apparatus and method for measuring the inductance of a wire-loop without direct reference to any particular time-constant or frequency. Low-frequency noise induced into the wire-loop is canceled within the detector circuit and crosstalk between a plurality of adjacent wire-loops is nullified using passive transformers. New wire-loop configurations utilize the permeability-modulated carrier referencing to provide repeatable inductive signatures with less intrusive, and non-intrusive installations.

Abstract: A system and method for measuring a plurality of successive induction measurements, collectively known as the “inductive signature” of a vehicle, and classifying the vehicle described by the measured inductive signature. The system includes a blade-type wire-loop configuration, or blade sensor and a corresponding measurement circuit employing a discrete measurement technique, as opposed to the frequency counting technique of the prior art. The system and method produce repeatable inductive signatures at a high resolution that allows for accurate identification and classification of a vehicle.

Abstract: An oscillator circuit for use with a wire-loop inductive sensor and method for use. The oscillator circuit includes two balanced capacitors coupled to the wire-loop sensor, and an excitation circuit connectable with the capacitors at a selected polarity. Wherein, when the excitation circuit is connected to the capacitors, one of the capacitors is charged while the other capacitor is discharged, and both of the capacitors are discharged when the excitation circuit is disconnected to produce a pair of decaying oscillations having a caduceus-shaped output. The oscillator circuit highly attenuates common-mode noise detected by the wire-loop and differential noise from both ambient and crosstalk sources is filtered by active isolation.