Magnetic field sensing in the underground construction environment

Industrial magnetic field sensing applications often address such problems as crack detection, gear tooth (or missing gear tooth) detection, tramp metal detection in a process stream, proximity detection, vehicle counting, and similar tasks. The general sensor community is little aware of another industrial application in which magnetic fields are used for short-range distance measurements and data communication in the underground construction environment. In such problems, the magnetic field sensor becomes an antenna for a magnetic field receiver. This paper discusses magnetic field sensing in two situations conventionally called locating and tracking applications encountered in underground construction. Problems of this type typically involve magnetic fields from line or dipole sources, respectively, giving equipment for each problem a particular physical structure and mathematical foundation.