A metal detector is a device for examining any metallic foreign substance such as iron, stainless steel, etc. abnormally incorporated by the application of electromagnetic induction phenomenon. You can separate the mixed metal contaminants from normal products by adding the appropriate rejecter to the metal detector.
A metal detector creates invisible electromagnetic field inside the detecting head to detect a microscopic change in the signal of electromagnetic field occurring when the metal passes through inside the electromagnetic field.
However, as a testing product containing water and salinity, can also change
the signal of electromagnetic field similarly to to a metal at the time of
metal detecting