Patent ID: 6487452
Filing Date: 2002-11-26
Classification: G01V

Abstract:
A circuit for detecting the presence of a permanent magnet in the vicinity of an active medical device comprising:a coil having a first inductance in the absence of a proximate permanent magnet and a reduced inductance in the presence of a permanent magnet proximate to the coil; a resonant LC circuit including said coil; a pulse generator for pulse excitation of said resonant circuit; means for analyzing a pulse response of the resonant circuit to said pulse excitation, and discriminating means, able to evaluate the value of the coil inductance resulting from the analyzed pulse response and, correlatively, to determine a presence and an absence of the proximate permanent magnet, characterized in that: the pulse generator comprises means able to deliver a burst of N successive pulses, and the analyzing means comprises means able to determine N corresponding pulse responses, and the discriminating means comprises means able to determine the presence of the permanent magnet if, among N determined analyzed pulse responses, a number M of said determined analyzed pulse responses correspond to said reduced value of inductance, wherein M is less than N.