How Does a Metal Detector Work?

How Does a Metal Detector Work

There are different types of metal detectors, and they all work differently. A regular metal detector uses a transmitter coil to help create an electromagnetic field when electricity passes through it. So, when moving the metal detector around, the electromagnetic field moves around in unison. When you move the metal detector over any metallic object, the magnetic field affects the atom in the metal, which makes another magnetic field appear around the metal. 

The metal detector has a receiver coil which is usually connected to a loudspeaker. When the electromagnetic field around the metal is detected, electricity would flow through the receiver coil which makes it beep through the loudspeaker. The closer the transmitter coil is to the metal, the stronger the magnetic field it creates which would increase the electricity passing through the receiver coil and also increase the beeping made through the loudspeaker.

Concepts involved with metal detectors

Frequency: This is a major characteristic of metal detectors. The frequency affects how well-intended targets can be detected. Usually, when a single frequency detector transmits at a high level of frequency, it is more sensitive to little targets. When this same single frequency detector operates at a low frequency, more depth is given on large metal objects. However, there are metal detectors that transmit multiple frequencies and are responsive to both small and large targets. 

Discrimination: This is the ability of a metal detector to discover buried targets using the conductive and ferrous properties of the metal. After identifying the target, you can either dig it out or continue your search. So discrimination helps determine the efficacy of the metal hidden beneath the soil. 

Ground Balance: This is a setting that increases the depth of detection in the soil. There are different types of soil, some contain salt which reacts the way metal does to the electromagnetic field produced by the transmitter coil. If there are small objects buried in these types of soil, the effect of the salt would prevent them from being discovered. To correct this, some metal detectors have ground balance settings which helps filter the ground signals from actual metal signals. Types of ground balance settings include; manual ground balance, automatic ground balance, and tracking ground balance.

Metal detector components and terminologies

Several factors must be in order for a metal detector to work appropriately. Some of these factors include;

Battery: The battery helps power the metal detector.

Transmitter coil: This is the device that transmits electromagnetic fields from the detector to the ground, and it also receives the magnetic fields coming from the metal.

Receiver coil: This is the device that transmits the electromagnetic fields coming from the metal to the loudspeaker on a metal detector. Hence, the beeping sound.

Control box: This is where the metal detectors electronics can be found. Here, electronic signals are transmitted and also received, which is then processed and conveyed to a target response.

Electromagnetic fields: This energizes the target metal to help ensure that they can be discovered by your metal detector.

Target: This is any metal object which a metal detector can detect.

Unwanted targets: These are metal objects that are not targeted but also react to the magnetic fields coming from the metal detector. The metal detector could be programmed to reject unwanted targets. So a response would not be provided for such targets. However, not all metal detectors can do this.

Metal electromagnetic field: This is the magnetic field that the metal produces when it comes in contact with the electromagnetic fields coming from the metal detector.

Target response: When a good target is picked up by the metal detector, it produces a response, it could be a beep or ringing noise.

How Metal Detectors Work

Usually, metal detectors make a loud beeping noise whenever they make a find. You should still move the detector around to determine the type of metal your detector has picked up. Here is how a basic metal detector works.

  • There is a battery on the top of the metal detector which activates the transmitter circuit. The circuit then passes electricity to the transmitter coil using a cable in the handle.
  • When electricity flows to the transmitter coil, it creates an electromagnetic field around it.
  • So when you are using your metal detector and you sweep above any metal object, the electromagnetic field would penetrate through it.
  • The electromagnetic field would cause the metal to also produce its magnetic field.
  • This magnetic field from the metal would then go to the receiver coil of your metal detector and then spark a buzz in the loudspeaker which alerts you that you just found a metal

How deep would a metal detector go?

There is no specific answer to this question. Several factors have to be put into consideration before you can discover how deep a metal detector would go. Some of these factors are:

  • Type, size, and shape of a metal object: The size must be taken into consideration because bigger items are much easier to find than smaller ones.
  • Age: This is also another feature which must be considered, metal object that has been buried for a long time would most likely be corroded and oxidized which makes it difficult for a metal difficult to pick them up.
  • Nature of soil: For beach sand, the metal detector would beep rapidly because of the type of soil/sand that it is used on.
  • Type of metal detector and frequency: This goes a long way in determining how deep your metal detector can go. A metal detector can either have a single or multiple frequency detector, and they can operate at low and high frequencies.
  • The object itself: If an object is close to the surface, but is facing downwards, a metal detector might not pick it up, but would pick an object lying flat that is buried farther into the soil.

A regular metal detector should detect within 10-20 inches of soil.

Where are metal detectors used?

Metal detectors can be used for much more than discovering hidden treasures. The 21st century has improved the uses of metal detectors. They can be found in airports, hospitals, banking halls, museums, and hospitals. They are used to ensure people do not bring in guns or any sort of weapons into these types of places. Archaeologists have complained about untrained people using metal detectors because the frequency could disturb important artifacts. When a metal detector is used properly, it becomes a very useful tool in creating and uncovering history.

Who invented metal detectors?

Back in the 1800s, Graham Bell made an invention that was used to detect the bullet lodged in the body of President James A. Garfield. Then, this device was called an induction balance, and this was the first case of a metal detector. Though the president died because the bullet was never found, Bell’s invention worked and people gave him credit for that.

While portable metal detectors were invented by an electronics engineer of German descent. He applied for a patent on this invention in 1933, and he called it a metalloscope. Gerhard Fischer who invented the metalloscope, is the founder of Fisher Research Laboratory which is at the pinnacle of metal detectors manufacturing in the world. While the first computerized metal detector was invented by Dr. Charles Garett and his company, this innovation secured its patent in 1987.

Non-metal detectors

Yes, there are non-metal detectors. Since metal detectors are now been used for security purposes, evil perpetrators have found a way to beat and smuggle weapons past this security measure. There are now weapons made from plastic, ceramics, and carbon fiber. These are completely undetectable for metal detectors. What is the solution to this problem then?

Airports and some museums use scanners that can pick up metallic and non-metallic objects. These scanners emit waves that can pass through clothing, but reflects the body and concealed weapons if there is any. It works like an X-ray machine but a more subtle one because X-ray machines use very powerful radiation which can be harmful to the body if the human body absorbs too much. So, these scanners pose no risks to those that they are used on and those that use them

Final thoughts

Metal detectors use magnetic fields to detect metal that is buried deep in the soil, so with the aid of electromagnetic fields, the exact position of the target metal can be detected by a metal detector, then it is up to the user to determine whether to dig out the metal or leave it because it is not worth going through the stress.

There have been some historic and wealthy discoveries made in the past decade, and these would not have been possible if metal detectors were never invented.