System and method including a buried flexible sheet target impregnated with ferromagnetic particles and eddy current probe for determining proximity of a non-conductive underground structure

摘要

Both a system and a method are provided which allows an eddy current probe to accurately determine both the proximity and dimensions of non- conductive structures which are normally invisible to such probes. The system includes a portable target medium that is movable into a known position with respect to the non-conductive structure, and that includes a conductive material that couples strongly with a fluctuating magnetic field, and a movable eddy current probe that emanates a fluctuating magnetic field and which generates a signal indicative of the magnitude of the interaction between the field and the portable target medium from which the distance between the two may be computed. The system may be used to determine the proximity of non-conductive structures such as plastic pipes that have been buried under ground, as well as the dimensions of such non conductive structures.