How Do Metal Detectors Work? (2020 Guide)

If you want to try out a new hobby, say, relic hunting or collecting coins, then you should know a thing or two about how metal detectors work. In this article, we are going to look at the operations of a metal detector and how to use it.

Metal detecting is a great hobby that everyone should try out. As metal detectors become better, more and more people are trying out relic hunting as a hobby. Relic hunting and metal detection are not as simple as hovering the detector over the ground. Practice makes it easier to find little metallic relics in the ground. Other than this, we know metal detectors as a security check-in public places such as airports and malls.

When metal detectors are used a security measure, they come in two forms: the huge walk-in metal detector where you place all metallic objects on your body on a separate pan, and as a small handheld machine that is run across your body to detect any weapons. Security metal detectors work as part of a larger security system that includes CCTV cameras, door controls, and x-ray scanners. In this article, we are going to focus on the more personal detectors that anyone can own; the relic hunting detector.

There are many types of metal detectors from simple basic ones to highly complex specialized detectors. They all work differently but all have a standard basic working system that we are going to discuss on this article. Whether you are a metal detecting enthusiast or not, you have probably at one point asked yourself “how does a metal detector work?” The truth is that many people, even enthusiasts, do not know the mystery of how a metal detector works. The following section highlights the basic working of a metal detector.

The Science Behind Metal Detectors

Metal detection technology was first used by a Scottish scientist named James Clerk in 1831. He discovered the relationship between electricity and magnetism that is the basis of a metal detector. James realized that when a copper wire is wrapped around a metallic nail and current passed through the coil, the nail becomes magnetized and can attract other metallic objects. Metal detection technology was built from this discovery. What happens in the coil and nail experiment is that; when current passes through the copper coil, a magnetic field is created. When the field hits a metallic object, it reflects back and can be pulled by the magnetized nail.

Types of metal detectors

how metal detectors work

 

 

Different metal detectors are used for different purposes. Because of this, metal detectors are built according to how much frequency they are required to produce. The more frequency required, the larger the detector will be. For the ground scouring metal detectors, their built depends on how deep in the ground you are searching and what kind of material the ground is.

The simplest detectors are the ones used for general purpose detection, treasure and relic hunting. They are referred to as very low-frequency detectors (VLF) because they use a single frequency of less than 30 kHz. Higher frequency detectors are known as pulse induction detectors. These are used for detecting deeper metallic objects in the ground. The third type of detectors are referred to as full and spectrum detectors. They use multiple frequencies at the same time, which is like using multiple detectors at the same time. The following section shows how the different types of detectors work.

Walkthrough security detectors

Walkthrough metal detectors use a feature known as pulse induction technology (PI). PI systems work by seeding short powerful bursts of current through the coil located on each side of the door. Each burst generates a short strong magnetic field. When the magnetic fields come into contact with metal on your body, it (magnetic field) is reflected back. This field hits the receiver on the coils. The receivers are connected to an alarm system such that when they detect the reflected field, the alarm trigger goes off. Although this process sounds long on paper, it happens in just a few microseconds. This is because a PI based detector sends about 100 pulses every second – this value can go up to 1000 pulses/sec depending on the model.

Regular metal detectors

For the regular handheld detectors used for relic hunting, the working is the same only with a different setup. In this detector, there are two coils in the search head of the detector. The first coil transmits and the other receives. What this means is that the first coil transmits a magnetic field that is powered by the detectors electric system. The second soil then receives the reflected field from the metal object in the ground. When this happens an alarm in the detector beeps to indicate there is a metallic object in that spot. This is facilitated by a cable and control box connected to the receiver coil. The weaker the reflected magnetic field, the weaker the beep alert will be.

 

Parts of a metal detector

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To fully understand how a metal detector works, you need to know what its main components are. In the previous section, we mentioned a control box which is just one of these parts. Although different detectors look different based on their purpose, they work basically the same way.

The following are the main components in any detector.

  • Shaft: The shaft is the main part of the regular detectors. It is the part where all other parts are connected to and is made to be adjustable for the user’s comfort
  • Control Box: As the name suggests, the control box is the main control area of the machine. It is the brain of the detector. It contains the device controls, the battery, settings, speakers and the microprocessor.
  • Stabilizer: The stabilizer is an essential part made for the user’s comfort. It acts like an armrest of the detector. It keeps the metal detector stable as you hover it over the ground.
  • Search coil: This is the bottom art of the metal detector that is held and hovered over the ground for treasure. It is basically an antenna that houses the transmitter and receiver coil. It is the integral that ‘detects’ metal.

Other parts include the speaker where alerts are sounded, the readout where you can connect the headphones and the handle.

Where are metal detectors used?

Metal detectors are used for more than recreational purposes. In fact the reason they became popular was to find weapons in the ground in war zones. Today, they are found almost everywhere from airports and malls to offices. They are used to prevent people from carrying weapons such as knives and guns into restricted areas such as airplanes. In smaller spaces such as malls, security guards are equipped with small handheld dtectors known as Super Scanners, most commonly made by Garrett Metal Detectors. It is ran across your body to detect any metallic objects. It is powered by a battery that provides up to 60 hours of run time. It uses a flashing LED light and a warped sound to alert the guard of a metal object. When a metal is detected the sound is produced and the LED lights flash in a certain pattern.

Archeologists also use metal detectors to scour the earth and find hidden historical tools and treasures. They have proven valuable in historic research.

How deep do metal detectors go?

There is no straight answer to this question since metal detectors are built differently. Other than this, there are many other factors that influence how deep a metal detector can go. Some of these factors include: the type and size of the coil, how mineralized the soil is, the frequency of the machine, the size of the metal, metal composition of the target and the discrimination settings of the detector. The following section shows in depth how these factors affect the depth of the metal detector.

The size and type of coil used

The detecting machines come with a standard coil but you can choose a different one at the shop. The size of the coil directly affects the depth of the detector and also affects sensitivity. The larger the coil, the deeper it will detect metal and the less sensitive the metal detector will be to small targets, whereas, the thinner the coil the more sensitive it will be to small targets while the depth detection is reduced.

The size of the target

The size of the target is directly proportional to the depth of your metal detector. The larger the target the more detectable it is.

How mineralized the soil is

This can be a huge problem for the metal detector. Soil contains different metals as we know although in little amounts. This is what is referred to as the mineralization of soil. The more mineralized the soil is, the less depth covered by the detector.

Conclusion

Metal detectors are a great invention that has helped humanity a great deal. The science behind how they work is simple and easy to implement. As time goes, metal detectors are getting better and better. They have been proven to be an effective way of maintaining security.

For underwater detecting, check our guide.

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