Measurement of soil conductivity using electromagnetic induction sensor

Promjenjivo magnetsko polje može u okolnim vodičima inducirati struju. Zavojnica s izmjeničnom strujom stvara promjenljivo magnetsko polje oko sebe. Osim struje u prijemnoj zavojnici, induciraju se i vrtložne struje u drugim vodljivim materijalima. Sekundarno magnetsko polje unosi promjenu faze i amplitude u prijemnu zavojnicu. Analognom i digitalnom obradom signala s prijemne zavojnice možemo odrediti iznos promjene. Osnovni prototip EM induktivnog senzora sastavljen je u laboratoriju. Sastojao se od jedne odašiljačke i dvije prijemne zavojnice. Signal sa prijemnih zavojnica je pojačan, anuliran, doveden do DAQ kartice i konačno na računalo gdje je obavljena digitalna fazno osjetljiva demodulacija. Senzor je na kraju detektirao promjenu vodljivosti testnih primjeraka, odnosno različite koncentracije soli (NaCl) u posudi s vodom. Dobiveni rezultati su se mijenjali sukladno s promjenom vodljivosti.A changing magnetic field can induce electrical current in the conductors nearby. A coil with alternating current creates a variable magnetic field around itself. In addition to the current in the receiving coil, there are also induced eddy currents in the other conductive materials around. The secondary magnetic field brings a change of phase and amplitude to the receiving coil. Analog and digital processing of the signal from the receiving coil can accurately determine the amount of change. A basic prototype of an EM inductive sensor was assembled in the laboratory. It consisted of one transmitting and two receiving coils. The signal from the receiving coil was amplified and brought to the DAQ card and finally to the computer, where a digital phase-sensitive demodulation was performed. The sensor finally detected a change of conductivity in the test specimens, which were different concentrations of salt (NaCl) in the water beneath it. The results were changing in accordance with the change of conductivity in the samples