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.

Operating a Metal Detector

Learning how to operate a metal detector will give you a much better understanding about how a metal detector works. The most common procedure of operating a MD is to hold it with one of your arm. Some of them can be heavy but manufacturers these days are now able to find ways to use lightweight and durable materials.

While holding your equipment, position the search coil on the surface of the ground. Take note, the search coil must not be resting on the surface of the ground where there must be an allowance or short distance apart. The reason is that, you will be sweeping the search coil from side-to-side.

Traditional MDs will generate an audible sound once you passed the search coil on a spot with buried metallic object. MDs that are enhanced with digital technology have visual screen offering some helpful information about the target such as depth, type of metal and etc...

Once you have located a target, the remaining task is for you to dig.


Metal detectors designed for the amateurs have only few basic settings. Some are even too simple to use where all you have to do is to turn it ON then you are ready for the search. Others have few settings consisting of a few buttons to press. For example, the Bounty Hunter Gold Digger has two modes of operation. First mode is to detect all types of metals while the second mode enable its Trash Elimination function.

However, MDs designed for the pros consists of several sophisticated settings. It would really take some time and constant practice before an average individual can fully understand and operate the equipment correctly.

Discrimination Setting

The discrimination feature of a MD allows you to differentiate metals which is very useful in avoiding junks. Sophisticated MDs offers the option for you to choose specific type of metals to be disregarded by your equipment. Without this feature, you will have to dig every target located by your MD.

Depth Setting

Only metal detectors used by professionals are equipped with Depth Settings. This is a feature that allows you to determine the depth of a certain buried target under the ground. With this feature, it will help you dig and uncover the object a lot much easier.

Ground Balancing

One of the most important setting of a MD that needs to be properly adjusted is the Ground Balancing. If you do not know it yet, soil or sands do have traces of elements such as iron and many other minerals. Some areas have higher contents of these elements while others have lower. The problem here is that, these elements causes interference responsible for generating false signals. As a result, you end up digging a target that is not there the first place.

Innovators of our time has taken a closer look into this issue and they found a solution through Ground Balancing technique. Most MDs that are available in the market today are now equipped with this feature. Advance models even has the capability to perform the task of adjusting itself automatically.


The application of microprocessor into MDs is the one that made huge improvements enhancing them with a more accurate detecting result. This component is found inside the control box responsible for every operation of the equipment. If it gets damaged then the MD will no longer be functional.

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.