MODE OF DETECTION OF METALLIC OBJECTS Russian patent published in 2007 - IPC G01V3/11 

FIELD: the invention refers to the field of detection of electric conductive bodies in nonconductive or poor conductive electric current mediums.

SUBSTANCE: the mode is based on excitation of metallic objects with an impulse magnetic field and recording the currents of the magnetic field caused by transitional processes in them. In quality of the source of excitation they use impulse succession of linear changing impulses of a triangular form of high linearity with an-off time ratio of impulses equals or more than 1,5. The impulses has an accumulation phase, a decay phase and a phase of absence of the magnetic field. The measurements are made during each phase with gating signals in no less then in two timely correlated positions in each phase. Each first selection is removed from the beginning of the phase on a time period defined by duration of fading of own transitional processes of the sensor. Each second selection is removed from each beginning of the phase on a time period equal or larger then the constant time of the transitional process of the object. At processing signals the difference of signals between the first and the second selection is calculated in each phase, absolute values of received differences in the first and in the second phase are summed up, filtered, intensified and used for detection objects by way of comparison with the threshold level.

EFFECT: increases sensitiveness and reduces influence of the excited field.

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