This method for detecting a disturber of magnetic field amplitude comprises:the emitting (62) of several magnetic fields of different frequencies from a same uniaxial magnetic field source, the amplitudes of the magnetic field emitted at two different unspecified frequencies being related to each other by a predetermined ratio,the measurement (64) of the amplitude of these magnetic fields at different frequencies by means of a same sensor, andthe reporting (70) of an amplitude disturber if a ratio between two of said measured amplitudes diverges from a predetermined threshold of the predetermined ratio which relates the amplitudes of the magnetic fields emitted at the same frequencies and, if not, the absence of any reporting.
