Discrimination of magnetic anomalies distributed by a given dipole

Research for submerged magnetic masses having dipole characteristics may be carried out with sensible magnetometers (for example, a nuclear magnetic resonance magnetometer) which emit respectively a signal whose frequency is proportional to the magnetic field and a voltage proportional to this frequency. The present study is devoted to the construction of an apparatus designed to be placed at the output of such a magnetometer with a view to automatic selection of these signals emitted which correspond to the masses under detection. The principle of this apparatus is based on the spectral analysis of a signal. In fact, the perturbations of interest occupy a frequency band extending from 0.037 Hz to 0.47 Hz, whereas the remainder are at lower frequencies. The output (or 'response') of the apparatus investigated takes the form of a pulse if the signal is of interest, if not it rests zero. This pulse permits the launching of the operation desired in the presence of the detected object (e.g. lighting of a beacon, installation of a buoy, etc.). (author)