How Metal Detectors Work?


The best way to explain "how metal detectors works" is to explain it in the most basic or general concept. It's because it would take us several pages to explain how those sophisticated MDs work.

All MDs are actually composed of three basic parts which are the battery, control box and the search coil. Let's explain them further:

MD Battery

Since metal detectors are designed to be taken outdoors, they require batteries as their main power source. And it's not just ordinary batteries, it must be batteries that could provide consistent power into the MD for a long duration period of time.


Some MD manufacturers even have their own manufactured batteries which are best recommended for their equipment.

Take note, there are some MDs that could get easily damaged when the wrong type of batteries are used. I already have two incidents where I tried installing 1.5 volts batteries into a MD that requires 1.2 volts batteries.

One common question when it comes to batteries is that, "Which one is better, a rechargeable or non-rechargeable battery?".

Based on my own personal opinion, a rechargeable battery is much better to use for MD because it can save you money and the hassle of going to the market to buy for replacements. Rechargeable batteries are indeed much expensive than the non-rechargeable, but rechargeable batteries tends to serve a longer period of use. They actually provide hundreds and even thousands of more hours which is comparable to buying several non-rechargeable batteries.

Aside from saving you some money, rechargeable batteries are also better for the environment. NiCad rechargeable batteries don't have much cadmium contents as non-rechargeable do. You have to know that non-rechargeable batteries are full of mercury, lead and cadmium which are bad for our environment.

Search Coil

The search coil of a metal detector is the part used by the operator in scanning the surface of the ground. What it does is that, it sends out a powerful electromagnetic field which penetrates the ground. If it happens that a certain object is on the spot, the transmitted electromagnetic field will first energize the object. Once fully energized, the object will send or deflect the signal back at the opposite direction.

Signal Transmission

As a result, the deflected signal will be picked up by the search coil and then processed by the control box into an audible or visual output.

Inside the search coil, it actually consists of copper wires that are tightly wounded. There are actually two sets of wounded wires, one is the transmitter (responsible for transmitting the signal) and the other one is the receiver (responsible for receiving the signal).

Search coil is an important part of a MD so you really have to take good care of it not to get damaged or disfigured. If this happens, the accuracy of your MD will be affected which could lead to poor results.

Control Box

The control box of a metal detector is like the brain of the equipment. It is the one that processes the transmitting and receiving of electromagnetic field into the search coil. And just like what I mentioned above, once a signal has been picked up, the control box will immediately convert the signal to alert the operator that a certain item has been found.

Control Box

Inside the control box, you will find electronic components such as resistors, capacitors, ICs and etc... If you know nothing about electronics, it's best not to tinker on them as this could lead to damages.

To sum it up, a metal detector works in a way that it transmit electromagnetic field down into the ground. Once the signal came across a certain metallic object, the signal will bounce back into the direction of the search coil. Then, the control box will process it into an audible sound.