How Do Metal Detector Coils Work?

Is there anything more fun than spending an hour or two searching for buried treasure?

Metal detecting, widely considered to be one the most relaxed yet fulfilling hobbies in the world, is an awesome way to discover valuable relics underground via the help of, you guessed it, a metal detector!

As you may already know, metal detectors use the exact same technology that security (and even military) services use to help keep us safe, and are essentially based on electromagnetism.

Nevertheless, as such mind-boggling pieces of equipment, many people often wonder how each of the different components of a metal detector works, with one of the most notable being the coil. 

So, whether you’ve been a fan of metal detecting for years and simply want to refresh your knowledge, or you’ve just recently taken it up as a hobby – this article will talk you through how metal detector coils work, as well as how they can vary, too. Whenever you’re ready, just read on.

How Do Metal Detector Coils Work?

In a nutshell, metal detector coils work by transmitting an electromagnetic field (triggered by the user of the metal detector) after they have been placed beneath the surface of the ground in which the user is metal detecting.

This coil is then able to emit the electromagnetic field, which “energizes” all metal objects within the field, which are then able to begin emitting their own electromagnetic field which the coil will be able to detect.

When the metal detector coil receives the returned electromagnetic field from the energized metal object(s) the search coil is then able to alert the user by creating a targeted response that will be unique to the metal detector being used.

Are There Differences Between Metal Detector Coils?

Even though all metal detector coils are made to serve essentially the same purpose, metal detector coils can vary in size, shape, configuration, and more, which can all affect the effectiveness of the coil.

Below, let’s take a look at some of the ways that coils can differ depending on the brand, overall quality, and individual models:

Coil Size

The coil size is one of the most important features to look out for, as it greatly determines how well the metal detector in question is going to be able to detect electromagnetic objects.

If coils are on the larger side, it often means that they are going to be able to offer a greater amount of sensitivity and depth as opposed to a smaller coil, which will often only be able to offer a limited amount of depth rating and sensitivity. 

Regardless of that, even though larger coils are usually deemed to be the better option, it doesn’t mean that they are all good. Larger coils have a much lower sensitivity to smaller electromagnetic fields as compared to smaller coils, which can raise the chances of you unintentionally missing valuable finds.

Luckily, many latest-generation metal detectors that feature larger coils do come with more sophisticated sensitivity toggles, which will allow you to make adjustments as and when you want to detect smaller objects. Nevertheless, it’s certainly something to keep in mind.

In contrast to this, while smaller coils are often limited to how far down they can detect objects, they do have a great ability to detect smaller objects that are less affected by electromagnetic interference (EMI). In addition to this, it’s also worth noting that smaller coils have the ability to be inserted into much smaller, awkward spaces that a large coil may be unable to fit in.

With all that being said, if you are planning to primarily metal detect for treasure or coins, then we recommend opting for smaller coils if you want to detect shallow targets, and a larger coil if you are wanting to cover a large surface area quickly. As for gold detecting, you will be best-suited with a large coil that will offer you maximum depth and sensitivity levels. 

Coil shape

Another major feature that can affect the overall effectiveness of a metal detector coil is the coil shape. More often than not, the most common type of coil shape that you will come across is circular coils, as these are widely considered to be the most effective, stable, and long-lasting.

In addition to circular coils, another popular type of coil shape used are elliptical coils, which are known to be one of the easiest out of all to move around and maneuver – even in the most awkward and difficult of spaces.

The third most common type of coil shape used in metal detectors is open-web coils, which are specifically used for water metal detecting, as the open design allows for a more seamless experience when passing through water.

Coil configuration

Last but certainly not least, another feature that can greatly affect the overall effectiveness of a metal detector coil is the configuration.

As of right now, the most common types of coil configurations are Monoloop, Double-D and Concentric. Let’s take a look at each one below:

Monoloop – 

A Monoloop coil features one winding loop directly around the outside of the coil, which both transmits and receives signals. For this reason, Monoloop coils are typically considered to offer the best depth out of the three kinds.

Double-D –

A Double-D coil consists of two wire windings that each resemble the letter “D”, hence the name. This type of coil configuration is known to be a great all-rounder and offers great stability, depth, and ground balancing.

This makes this type of configuration best suited for all types of metal detecting, although it should be noted that it’s particularly well suited for areas of high EMI.

Concentric –

A concentric coil is able to transmit via winding directly outside the coil and winding on the center of the coil.

This allows the winding to create a cone-shaped pattern that makes it the most ideal configuration for precision.



Written by Gavin Bowler

Keen history and blogging enthusiast. I love metal detecting. Read more of Gavin's articles.