How Metal Detectors Work?

As if the metal detector types and brands were not enough, there are also several very different
technologies powering each of these machines. Each major manufacturer will have their own
technologies at work deep inside each of their flagship machines. This type of competition
amongst metal detector manufacturers makes it great for consumers like us.

Each metal detector manufacturer is trying to outdo each other. The end result of this constant
competition are the advanced machines that we use to locate treasure. Lucky us, but what is
happening underneath the buttons and knobs? How does this machine do what it does? The
answer to this question is frequencies.

When you power on your favorite metal detector, the search coil goes to work. It creates an electromagnetic field that penetrates the surface of the earth. The electromagnetic field consists of different frequencies. Each metal detector manufacturer uses different electronics to transmit these frequencies into the ground.

When these frequencies come into contact with a metal object, something happens. The metal
object creates its own electromagnetic field that bounces back towards the metal detector coil.
The metal detector coil is designed to pick up these secondary frequencies and process them
into information that we can work with.

That information may be an audible beep, a number or an image on a screen. This information
is what we use to determine that a target is buried somewhere under the coil of our metal detector. Your metal detector is not only sending out massive amounts of frequencies. It is also
receiving them as well. Check out the image below.

scheme of how a metal detector functions

I have often wondered how certain animals respond to these electromagnetic frequencies. I
have spent a lot of time metal detecting in and around salt water beaches. I have seen my fair
share of sharks while metal detecting these beaches. Sharks are known to respond to electrical
impulses in the water around them. This is how they locate their prey.

How does a shark see a metal detector emitting all of these frequencies? If you happen to
figure this out and invent the world’s first working shark repelling device based on this concept, remember where you got the idea.

Which frequencies work best for treasure hunting?

It would be nice if every metal object reacted to the same frequencies, but that is not the case.
That would make things too easy for metal detector manufacturers. Different frequencies have
very different effects on the ground and metal objects buried.

Low frequencies are great at going very deep. They respond well to larger objects too. Low
frequencies are excellent at locating big items and highly conductive metals like gold, silver
and copper. This may sound like the winning choice, but low frequencies are not very good at
locating smaller objects.

Medium range frequencies are great for all purpose general metal detecting. They go deep and they respond well to both large and small targets.

High frequencies are great at finding smaller things like small gold nuggets and thin gold

So it looks like you have another choice on your hands. Should you get a machine that uses
low, medium or high frequencies? Luckily there are machines on the market that can handle all
of them at once! These are the more expensive multi-purpose machines that have been designed to work in multiple ground conditions on multiple targets.

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