Metal detectors how does it work

Wonder What's Next? Better bring an umbrella! Find a friend or family member and explore one or more of the following activities: What types of things are made of metal? Sure, there are a lot of plastic items in the world today, but there are still plenty of things made out of metal. Go on a scavenger hunt today to look for metal objects. Take pictures or make a list of what you find. Challenge a friend or family member to join you in the hunt.

Ask family members if they can think of objects that used to be made of metal, but aren't anymore. Do you like playing with magnets?

Perhaps you have some on your refrigerator that you use to display your best pieces of homemade art work. Did you know that you can also use them for scientific purposes? It's true! Check out Magnets and Metal online to read about several different science experiments you can do with magnets and a few simple objects. Have fun and share what you learn with a friend or family member.

Up for a challenge? Have you ever lost a coin or a piece of metal jewelry when you were playing in the sand at the beach? Maybe you've dropped an earring in the tall grass while on a hike? Without a metal detector, these items might have been lost for good. You don't need to buy a metal detector to search for lost items such as these, though. All you need are a few spare items you probably have around the house. Do you have an old AM radio, a simple handheld calculator, a compact disc case and some Velcro?

Just watch the video at the link above and you'll be searching for lost items in no time. The fact is that all of these scenarios are valid. Metal-detector technology is a huge part of our lives, with a range of uses that spans from leisure to work to safety. The metal detectors in airports , office buildings, schools, government agencies and prisons help ensure that no one is bringing a weapon onto the premises. Consumer-oriented metal detectors provide millions of people around the world with an opportunity to discover hidden treasures along with lots of junk.

In this article, you'll learn about metal detectors and the various technologies they use. Our focus will be on consumer metal detectors, but most of the information also applies to mounted detection systems, like the ones used in airports, as well as handheld security scanners.

Most systems also have a jack for connecting headphones, and some have the control box below the shaft and a small display unit above. Operating a metal detector is simple. Once you turn the unit on, you move slowly over the area you wish to search. In most cases, you sweep the coil search head back and forth over the ground in front of you.

When you pass it over a target object, an audible signal occurs. More advanced metal detectors provide displays that pinpoint the type of metal it has detected and how deep in the ground the target object is located. In the following sections, we will look at each of these technologies in detail to see how they work. Very low frequency VLF , also known as induction balance , is probably the most popular detector technology in use today.

In a VLF metal detector, there are two distinct coils:. The current moving through the transmitter coil creates an electromagnetic field, which is like what happens in an electric motor. The polarity of the magnetic field is perpendicular to the coil of wire. Each time the current changes direction, the polarity of the magnetic field changes. This means that if the coil of wire is parallel to the ground, the magnetic field is constantly pushing down into the ground and then pulling back out of it.

As the magnetic field pulses back and forth into the ground, it interacts with any conductive objects it encounters, causing them to generate weak magnetic fields of their own.

The polarity of the object's magnetic field is directly opposite the transmitter coil's magnetic field. If the transmitter coil's field is pulsing downward, the object's field is pulsing upward. The receiver coil is completely shielded from the magnetic field generated by the transmitter coil. However, it is not shielded from magnetic fields coming from objects in the ground. Therefore, when the receiver coil passes over an object giving off a magnetic field, a small electric current travels through the coil.

This current oscillates at the same frequency as the object's magnetic field. The coil amplifies the frequency and sends it to the control box of the metal detector, where sensors analyze the signal. The metal detector can determine approximately how deep the object is buried based on the strength of the magnetic field it generates. The closer to the surface an object is, the stronger the magnetic field picked up by the receiver coil and the stronger the electric current generated.

The farther below the surface, the weaker the field. Beyond a certain depth, the object's field is so weak at the surface that it is undetectable by the receiver coil. In the next section, we'll see how a VLF metal detector distinguishes between different types of metals. How does a VLF metal detector distinguish between different metals? It relies on a phenomenon known as phase shifting. Phase shift is the difference in timing between the transmitter coil's frequency and the frequency of the target object.

It wasn't until the s that the development of metal detectors began to pickup pace though. The first patent for a metal detector was awarded to Gerhard Fischer in , although it was improved by a variety of inventors over the years. Lieutenant Jozef Stanislaw Kosacki, for example, refined the design into a machine that was more practical - albeit considerably heavier than modern machines. Today, the top models have features such as a computerized design and integrated circuit technology to allow the user to fine-tune their detection parameters.

There are different types of metal detector, and one of the most important for hobby detecting is the pulse induction PI detector. Unlike VLF detectors, these usually have just one coil that acts as both the transmitter and receiver. Short pulses of current are passed through the single wire, which creates a magnetic field. Once the pulse is switch of, the field collapses which causes a spike in electricity, resulting in another short-lived current.

If the detector is near a metal item, the detector's sampling circuit picks up the opposite magnetic field. It can detect the metal as the second pulse called the reflected pulse takes longer to fade away.

While pulse induction technology provides greater depth and decent sensitivity for gold, there are a few downsides. Most PI detectors aren't suitable for use in urban areas, as they can't identify or ignore iron "trash. They are better for hunting in rural locations though, and can provide a deeper search. They are also great for beaches and other environments that contains highly conductive material.

There are also beat-frequency oscillator BFO metal detectors. These are the cheapest and least complex. Many industrial detectors, for example, have a three coil design. This configuration allows the instruments to detect tiny pieces of metal. This is a difficult question to answer. In general, the maximum depth is around cm. A detectors maximum depth can vary depending on several factors though:. Additionally, some metal objects cause the conductivity of the surrounding soil to increase over time.

This is called a halo. Metal detectors are used for a variety of purposes and come in many forms. Some of the most common include:. Metal detectors can look intimidating to the newcomer, but they don't need to be complicated - or even expensive.

It's true that modern detectors are becoming increasingly advanced, but in many cases you can get started by only knowing the basics. Some of the best beginner detectors are relatively cheap, and allow you to hunt for artifacts, coins and other objects with a great chance of success.

If you're interested in picking up the hobby, click the button below for my list of the best metal detectors or check out my list of beginner detectors here. Be warned though - metal detecting can be addictive! How Deep Can Objects Be?

Treasure Talk. Success Stories. Support Support. Learn GPX Product Warranty. Where to Buy. How Metal Detectors Work. Transmit Electromagnetic Field visual representation only - blue The transmit electromagnetic field energises targets to enable them to be detected. Target A target is any metal object that can be detected by a metal detector. Unwanted Target Unwanted targets are generally ferrous attracted to a magnet , such as nails, but can also be non-ferrous, such as bottle tops. Receive Electromagnetic Field visual representation only - yellow The receive electromagnetic field is generated from energised targets and is received by the search coil.

Target Response visual representation only - green When a good accepted target is detected the metal detector will produce an audible response, such as a beep or change in tone. Key Detecting Concepts Frequency The frequency of a metal detector is one of the main characteristics that determines how well targets can be detected.

There are three main types of Ground Balance: 1. There are four main types of discrimination in Minelab detectors: 1. Return to Top. Become a Dealer Countermine Login. Find Treasure Strike Gold. Yes No.