Horizontal electromagnetic field sensor for detection and classification of metal targets

This paper describes a prototype electromagnetic induction (EMI) sensor system designed specifically to measure the horizontal component of a metal target's eddy current time decay signature. Instead of creating a vertical magnetic field from a horizontal loop transmitter configuration used by most EMI metal detectors, the prototype transmitter geometry has been designed especially for creating a horizontal magnetic field (HMF). One of the potential advantages of the HMF sensor is the relatively uniform magnetic field that is created over a large volume. A second potential advantage is that, compared to a conventional loop antenna, the magnetic field intensity falls off slowly with distance from the plane of the sensor. These two advantages potentially make the HMF sensor well suited for detection and classification of metal targets buried deeply in the ground (e. g., unexploded ordnance, UXO) or from a vehicle-mounted mine detector sensor. Preliminary modeling of the antenna and laboratory data from a time-domain version of the HMF sensor are presented.