This study investigated the feasibility of using Anisotropic Magneto-Resistive (AMR) magnetometers to detect train or vehicle presence and to determine train speed for the activation of grade crossing warning systems. Laboratory, parking lot, and railroad field tests were performed using 3-axis digital AMR magnetometers for train and vehicle detection as well as speed measurement. It was determined that the sensors drift with changes in the ambient temperature. However, by periodic bias removals (auto-calibrations), the impact of these bias drifts can be eliminated. It was also determined that the detection distance for vehicles depends on the amount of magnetic material (iron, nickel, or cobalt) and varies as the inverse cubed (third) power of the distance from the sensor. Changes in the ambient electro-magnetic field such as caused by variable current power lines, are also detected with an inverse (first power) distance relationship. Hence, electromagnetic interference may travel a longer distance than a magnetic signature, depending on the magnitudes of these two signals. Overall, it was found that the 3-axis measurement capability of the AMR magnetometers permits the unique identification of different vehicles. It also permits the separation of vehicle signatures from noise signatures. Hence, these magnetometers provide an alternative, more flexible, approach for activating crossing warning systems than the current use of track circuits.


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    Title :

    Magnetometer Sensor Feasibility for Railroad and Highway Equipment Detection. High-Speed Rail IDEA Program


    Contributors:
    J. Brawner (author) / K. T. Mueller (author)

    Publication date :

    2007


    Size :

    37 pages


    Type of media :

    Report


    Type of material :

    No indication


    Language :

    English