ELi5: How does a metal detector work, and specifically how does it detect non-ferrous objects?
In: Physics
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Electromagnetic Induction is the base principle in use here. Any electrical field creates a temporary magnetic field and vice versa.
The metal detector has a coil that generates a rapidly fluctuating magnetic field. This induces eddy currents in the close proximity metal surface. Those induced eddy currents generate their own temporary magnetic fields. These magnetic fields are exposed to the metal detector coil and in turn induce an eddy current in that coil. This induced current is measured / sensed and alarm is triggered.
Non-ferrous metals are non-magnetic but good conductors. So eddy currents are induced in them too. And the eddy currents produce their own magentic fields too.
So, in principle, there is no difference in the way (leaving aside the sensitivity aspects) the metal detector works for ferrous or non-ferrous metals. If it is working on a electromagnetic induction principle – it can detect anything within which it can induce a decent amount of eddy current.
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