Method for measuring the impedance of a grounding system that comprises a loop, the method comprises: for each frequency fi of a set of frequencies F, of a frequency sweep applied to the loop of the grounding system: - generating a modulating signal S signal with a fixed frequency fm, preferably fm = 220 Hz; - generating a carrier signal S carrier with the frequency fi; - obtaining an amplitude modulated signal S modulaled with frequency components of the frequencies fm and fi based on S signal and S carrier; - inducing the signal S modulaled in the loop of the grounding system; and - measuring a signal S out based on the signal S modulaled in said loop of the grounding system; - demodulating the signal S out, eliminating the carrier signal S carrier; - filtering the signal S out in a frequency fm tuned way to obtain a demodulated signal S demodulaled at the frequency fm based on S signal; - obtaining an impedance Z ( fi) of the grounding system based on the demodulated signal S demodulaled; wherein obtaining the impedance Z (fi) of the grounding system based on the demodulated signal S demodulaled comprises calculating a modulating index m = S demodulated S carrier 1 based on the demodulated signal S demodulated, wherein the modulating index m is defined as the ratio of amplitudes, - obtaining a phase measurement φ ( fi) based on the respective demodulated signal S demodulaled for each frequency fi; and obtaining for the set of frequencies F a Bode plot based on Z ( fi), φ ( fi), and the modulating index m of each frequency fi, respectively. - generating a modulating signal S signal with a fixed frequency fm, preferably fm = 220 Hz; - generating a carrier signal S carrier with the frequency fi; - obtaining an amplitude modulated signal S modulaled with frequency components of the frequencies fm and fi based on S signal and S carrier; - inducing the signal S modulaled in the loop of the grounding system; and - measuring a signal S out based on the signal S modulaled in said loop of the grounding system; - demodulating the signal S out, eliminating the carrier signal S carrier; - filtering the signal S out in a frequency fm tuned way to obtain a demodulated signal S demodulaled at the frequency fm based on S signal; - obtaining an impedance Z ( fi) of the grounding system based on the demodulated signal S demodulaled; wherein obtaining the impedance Z (fi) of the grounding system based on the demodulated signal S demodulaled comprises calculating a modulating index m = S demodulated S carrier 1 based on the demodulated signal S demodulated, wherein the modulating index m is defined as the ratio of amplitudes, wherein obtaining the impedance Z (fi) of the grounding system based on the demodulated signal S demodulaled comprises calculating a modulating index m = S demodulated S carrier 1 based on the demodulated signal S demodulated, wherein the modulating index m is defined as the ratio of amplitudes, - obtaining a phase measurement φ ( fi) based on the respective demodulated signal S demodulaled for each frequency fi; and obtaining for the set of frequencies F a Bode plot based on Z ( fi), φ ( fi), and the modulating index m of each frequency fi, respectively.