System and method using portable wall engaging ferromagnetic particle impregnated target medium for electromagnetically measuring distance between oposing walls of a 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 comprises 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. When the system is applied to measure the dimensions of such a structure, the portable target medium assumes a form that is flexibly conformable to one of the walls of the structure and which is placed in abutting relationship thereto. The eddy current probe is then scanned against an opposing wall of the structure, whereby the width of the structure may be computed by measuring the strength of the interaction between the probe and the medium. In addition to measuring the dimensions of non-conductive structures, the system may be used to measure the dimensions of non-magnetic structures when the target medium includes a strongly magnetic material.