Patent ID: 7443156

Claim:
A method for locating a metallic object or for identifying defects thereon, comprising the steps of: energizing at least one transmitting coil with an AC voltage for transmitting a carrier signal to the object and receiving at least one of an essentially amplitude-modulated received signal and phase-modulated received signal resulting from the carrier signal by means of at least one receiving coil, and demodulating the received signal using a computer and a Fourier or wavelet transformation method using a predefined number of digitally determined measurement results, calculating at least one of an associated magnitude value and phase value for the frequency of the carrier signal, and using the calculated at least one of an associated magnitude and phase value as a direct measure of one of a present signal strength and a phase angle of the demodulated received signal; wherein said demodulating step comprises multiple demodulating of the received signal using the computer and the Fourier or wavelet transformation method; wherein said calculating step also comprises calculating of a spectrum when the at least one of associated magnitude values and phase values are calculated for frequencies of the carrier signal; and wherein at least one additional frequency component of said spectrum is used with the calculated at least one of the magnitude and phase values as said direct measure one of the present signal strength vector and phase angle of the demodulated received signal.