Metal detector technology & how it works

Metal detector technology

Most consumer-grade metal detectors use an older technology called VLF (very low frequency) detection. A VLF detector uses electricity and magnetism to generate an audible signal when something is detected.

How it works?

Metal detectors have two coils, a larger transmitter coil and a smaller receiver coil. When activated, electricity flows into the outer transmitter coil, creating an electromagnetic field. This magnetic "glow" is what metal objects pick up on to identify themselves.

Once the transmitter has “excited” any metallic objects in the ground, a smaller receiver coil takes over. This coil looks for any changes in the magnetic field of the charged ground and detects metal objects, sending a signal to a loudspeaker which issues a tone based on the characteristics and strength of the charged metal.

Discriminator

A lot of high-end metal detectors have a microprocessor-controlled analyzer known as a discriminator. The discriminator compares the signals sent by the receiver coil to the known signals of various metals, like gold and aluminum.

A discriminator can be set to ignore signals from common metals, such as steel and aluminum. This allows the user to find more valuable metals that may be lurking underground, such as gold and silver.

Search parameters

The models on our shortlist offer various search parameters based on what the intended audience needs. For example, a child searching for quarters on the beach has different needs than an adult treasure hunter in the field.Here are some questions to ask yourself when evaluating different products:

What is the metal detector’s coin depth?

This is a measure of how deep underground the device can actually detect coin-sized pieces of metal. Not all manufacturers provide this information. Bounty Hunter advertises that its TK4 can detect coins eight inches down; the Time Ranger is advertised as having a nine-inch coin depth.

Is it waterproof?

Some metal detectors are completely waterproof, some up to 10 feet. Others have waterproof coils but cannot be submerged. Some cannot be used near water at all.

How big are the coils?

Metal detector coils come in a variety of sizes, but the most important thing to consider is how much ground you can cover. Smaller coils are good for pinpointing objects, but not as good at scanning large areas. Larger coils help cover larger areas more thoroughly, but if you sweep too quickly, you might miss something.

Special features

There are many metal detectors on the market today, but they all have different features. When you are considering a purchase, it is important to look for these special features. These features may not appeal to you, but it’s nice to know what you are getting into with the product.

Volume knob

A metal detector will make frequent beeps. If you want to control the volume, a volume knob is what you'll need.

Headphones/headphone jack

This was a somewhat noisy hobby. If you’d rather keep your business to yourself, look for a detector with a headphone jack. Some products included headphones, too. However, the price of a complete kit is higher than the price of a lone detector.

Sensitivity knobs

Many metal detectors offer different sensitivities, which you can adjust to filter out junk and get a better read on what you’re looking for.

LCD screen

Some models do not have an LCD screen, but this is a great place for the user to gather information.

Ground balancing

This feature allows you to tune out interference from natural metals in the soil, such as iron.

Custom notching

Notching is not discrimination. It is a way to filter out some unwanted results. However, a bad notching system could lead to missed findings.

Metal detection and the law

You don’t need a license to own a metal detector, but there are some general rules and regulations that apply to metal detector use.

Some cities allow amateur metal detectors to search public properties such as fairgrounds, city parks, and beaches. The ground must be returned to its original condition no matter what is found.

Some states require hobbyists to register before searching public properties, while others allow them to search with no restrictions. Be sure to consult your local government agency before searching for treasure on public property.

If you’re going to search private property with a metal detector, the owner must first give permission. The owner can add conditions to your use of his/her land, such as ownership rights or time limits.

If you're on private property and want to search for antiquities, make sure that the site is protected by an antiquities law. If it is, don't remove anything from the site.

Penalties for violating these laws and restrictions can range from a stern warning to thousands of dollars in fines. Amateur metal detectors are urged to do their research before starting any search on property owned by either the private or government.

Where you can hunt

With all of these restrictions, it might be hard to figure out where you can actually use your metal detector. The truth is that there are still areas that are open to hobbyists. The key is finding places where people have lived, worked, or played. Consider these areas:

• Schoolyards
  
• Old home sites
  
• Former factories
  
• Beach fronts
  
• Amusement parks
  
• Recreational lakes
  

Metal detectors are often used on beaches. Some states allow metal detection on sandy beach areas between the water and the dune line, while others require searchers to obtain special permission before gaining access to state parks and bodies of water.

Ergonomics & performance

If you're going treasure hunting, you need a machine that's comfortable to use for the long, grueling hours of searching. Here are some features to look for in an ergonomically sound metal detector:

Adjustable length

Some metal detectors have a built-in length adjustment. This can be adjusted based on the arm size of the user.

Weight

How much does the metal detector of your choice weigh? It may seem like a small matter, but if you plan to spend an afternoon waving the detector around, you'll probably want something that doesn't strain you. Anything around four pounds will work best.

Battery requirements

A metal detector requires batteries and few are rechargeable, so be sure to check your owner's manual for the specific needs of your detector.

Tips

• Before you go treasure hunting, be sure to understand the correct settings and capabilities of your metal detector. Read through the manual and research online if needed.
  
• Metal detectors work best when swung slowly side to side. The detector should be kept close to the ground, but not touch it.
  
• Similar to having the right tools for hunting, your choice of clothes is important when you are on a hunt. Wear comfortable clothes that are appropriate for the weather, knee pads if you will be digging, shoes that help you wade through terrain, and gloves for your hands so you don't get them dirty or cut yourself when scooping up soil.
  
• Before you start metal detecting, make sure you educate yourself on local laws to know which areas are permissible and the kind of digging that is allowed. Public areas may not allow metal detection if they have landscaping that could be destroyed.
  
• If you're new to metal detecting, be prepared to find more trash than treasure. However, don’t lose hope because you never know when luck may change and your excitement will come back. That's part of the appeal of metal detecting--the thrill of not knowing what might turn up next.
  

FAQ

Q: How deep will a typical metal detector penetrate the ground?

A: The answer to this question depends largely on the detector's make and model, but in general, the average detector can find larger pieces of metal 12 to 16 inches below the surface. Deeper searches would require a more powerful device, such as a ground-penetrating radar.

Q: Do I need a special kind of metal detector to hunt for gold?

A: While most metal detectors can detect the presence of gold in a general sweep, many discriminators have difficulty tuning out other metal signatures. This is why dedicated gold hunters often purchase a special metal detector designed to “listen” specifically for smaller gold fragments.

Q: Metal detecting seems very straightforward to me. What do the pros know that I don't?

A: For one thing, experienced hobbyists and professionals use different types of sweeping and search patterns. They can tell the difference between valuable metal hits and “trash” hits by the subtle changes in signal tones. Mastery of metal detection takes time, patience, and practice.