??????: ????????? ?????????? ????? ?? ?????? ?????? ???????.?? ???? ?????? ???? ?????? ???? ???? ?????? ??????? ??????? ??????? ???????? ??????? ????? ????? ??? ?????? ?????????? ??? ???? ??????.As a result of eddy currents induced while in the metal, a signal is detected when metallic is current. The fact that every metallic has a different stage