Metal Detectors

A guide to their history, functions, types, and selling points

Nearly everyone has dreamed of digging up lost treasure—especially kids! But not everyone has an old map with a big X to mark the spot. So, for those who want to experience the thrill of discovering buried loot or holding history in their hands, metal detectors are the next best thing.

Metal detecting is one of those hobbies that can be enjoyed by the whole family as well as pursued by individuals. It’s outdoor fun that requires concentration, problem solving, and patience. The pace is slow. The terrain varies. It can be addictive as well as rewarding. It even has its own code of ethics. Plus, it’s a form of outdoor exercise.

But what if your customers have in-depth questions about metal detectors or need a recommendation? Well, it’s time for you to become the expert!

When was the metal detector invented?

It’s the Nineteenth Century. Scientists realize that electricity can be used to pinpoint the location of metal, and what a boon that could be for mining operations! However, early machines were crude, battery hogs, and not particularly effective. Gustave Pierre Trouvé from Paris took a different approach. In 1874, he built a prototype of a handheld device. Its purpose was two-fold. It could be used to detect metal fragments inside injured patients as well as aid miners.

Jump forward to 1881. President James A. Garfield is shot in the back. Doctors cannot find the bullet in order to remove it. Alexander Graham Bell, who knew of Trouvé’s invention and was trying to improve it, offers to locate the elusive bullet with a device of his own making. He tries his best but is unable to locate bullet with certainty. Garfield later dies from infection, not from the gunshot itself. Later, others speculate the metal bedsprings interfered with the signals.

In 1931, German immigrant Dr. Gerhard R. Fisher set up shop in his garage, founding Fisher Research Labs. Soon after came the Metalloscope. It’s certainly a far cry from today’s more lightweight and streamlined devices! But it jumpstarted the hobby worldwide.

Today’s metal detectors incorporate the developments from many other individuals, resulting in a very different look. But Fisher is credited with the first portable device available for purchase. Fisher Research Labs is currently owned by First Texas Products, which also owns Bounty Hunter and Teknetics metal detector brands.

How do metal detectors work?

The overarching scientific principle at work is that metal, when energized, transmits an electromagnetic field. So, a metal detector creates electricity and sends it through a transmitter coil to create an electromagnetic field that is projected toward the ground. A buried metallic object then creates its own electromagnetic field in response. The receiver coil picks up that secondary field and turns it back into electrical responses. These responses are interpreted in different ways—by a tone, and sometimes by a Target ID numerical value or some kind of visual display.

The frequency or frequencies emitted by a detector affect how well it finds certain targets. Generally speaking, low frequencies are better for large objects while high frequencies are better for small objects. There are other factors that can affect performance such as type of soil (and the minerals and salts dissolved within it), electrical interference from other sources, how deep things are buried and their orientation, and so on.

What do metal detectors detect?

Many people think a metal detector can only detect ferrous or iron-based objects. But that’s not true. It can detect all kinds of metal, magnetized or not. So, nickel, bronze, brass, copper, lead, tin, zinc, silver, gold, iron, and aluminum objects can be located.

The real question is how responsive they are to electromagnetic fields. For example, stainless steel and titanium are not good conductors of electricity nor are they magnetic, so they are difficult to locate. Same with pearls, bones, gemstones, stone, and paper. Aluminum, on the other hand, easily conducts electricity even though it is not magnetic. Pull tabs from aluminum cans are a common find.

Sometimes, certain metals require more specific settings or a specialized detector in order to be located more easily.

Found objects can include rings, jewelry, coins, and historical items (known as relics) like musket balls, buckles, old nails, Civil War weapons, and more.

As a result, common subgroups of detecting include:

• Coin shooting—looking for coins after major contemporary events or searching for coins in general, whether current or old
• Prospecting—looking for valuable metals
• Relic hunting—looking for items of historical value
• Treasure hunting—looking for hidden caches

What are the types of metal detectors?

There are several types. Three common ones are:

1. BFO or Beat Frequency Oscillator. Entry-level detectors typically contain a BFO. It has a large coil in the search head and a smaller one in the control box. Each has a pulse oscillator but on slightly different frequencies. The pulses generate radio waves to create audible tones. The tones change when a magnetic field interferes with them. They are also not as accurate or as controllable.
2. VLF detectors. These are quite popular and tend to be the most common. These Very Low Frequency devices use a single frequency between 6 to 30 kHz and rely on phase shifting between the transmitted and received signals. VLF detectors are a strong muli-purpose option. They even work on dry sand. These devices are sometimes also called Induction Balance detectors.
3. PI or Pulse Induction. This generally uses a single coil that’s both transmitter and receiver. It pulses its signals and uses higher frequencies. This kind of detector is better for things deeper in the ground, soils with higher mineral content, and on saltwater beaches.

What is the best metal detector for beginners?

Most avid detectorists recommend setting a budget first. According to smarterhobby.com, “Most new hobbyists tend to spend $150-$300 on their first detector. Luckily, that buys just enough machine to get you hooked.”

And for those with deeper pockets, detectors costing under $600 bring a lot more to the table. Plus, from a practical standpoint, if there’s any doubt that interest in the hobby will quickly fade, there’s no point in starting with top of the line. One can always upgrade later.

Next, a first-time buyer needs to decide what type of things he or she wants to locate. As most newbies want to find coins and jewelry, single-frequency VLF detectors, the most common type, are ideal, plus fit into those dollar brackets mentioned above. There are even detectors geared toward children. They are lighter in weight and have simpler controls.

Bounty Hunter, a First Texas brand like Fisher, has a convenient chart that breaks out many of their products by how experienced a detectorist is. The Gold Digger and Quick Silver brands, by the way, are not specifically targeted toward those metals but are simply branding terms.

How deep do metal detectors work?

Detectors find things buried 8 in. to 20 in. deep. But there are a lot of variables. Shape, size, and type of object and its orientation are all major factors. A big, flat object near the surface can be deeper down and still be located vs. a small, skinny object in a vertical orientation. Soil type and the type of detector/frequency also are important.

Also, the bigger the coil on the detector, the deeper into the ground its signals will reach. Therefore some manufacturers say to measure the diameter of the coil. That number will give you the depth the detector’s signal can reach.

Where can I metal detect?

It’s best to search areas that constantly get new materials or areas that haven’t been searched at all. However, there are legalities. And these vary widely by location. General rules of thumb are:

• Public beaches
• High-activity locations
• Parks—however, these may require permission
• Backyards of friends—with permission
• Private land—but only if you get permission from the landowner

The best way to get a feel of acceptable places is to join a detectorist club. They are located all across the country. Resources to find ones nearby include http://metaldetectingintheusa.com/metal-detecting-clubs.html.

What features to look for

Like many hobbies, metal detecting uses niche terms. Plus, there is a wide variety of models and features, even within specific brands. But there are some common terms used across all metal detectors. Understanding these will go a long way to making a more-informed first choice. 

• Operating Frequency: VLF detectors can come in a variety of single frequency models. 5 to 10 kHz range are just fine for all-around hunting, as are those up to 30 kHz.

• Weight. For children, seniors, and those just getting started, a too-heavy detector will make swinging it a chore and cut down on time spent in the field. Therefore, this can be an important consideration.

• Discrimination and Notch Discrimination. These settings help the detector to ignore certain conductivity levels. This may not be available on many multipurpose detectors.

• Depth Indicator. This can let a user know about how deep they need to dig into the ground to find the object. Minimal surface disturbance is good etiquette and requires a precise cut. There are accessories that can help with this too, which we’ll touch on shortly.

• Ground Balance. When the soil has a lot of dissolved minerals, the effectiveness of a metal detector diminishes. Many starter detectors come with a preset ground balance for average ground conditions. More advanced ones have automatic ground balance, which adjusts to the actual soil conditions. Some models even feature a manual ground balance.

• Target ID. A metal detector can’t identify what its found. But many of them can give a hint. There might be a signal strength indicator or an assigned numerical value. Even tone-only ones utilize varying audio qualities, depending on the metal type. Experts suggest that beginners bury different types of things in the backyard and learn how their metal detector responds to each of them as a great way to train the ear.

• Search Coil. These come in all sizes and different technologies. Bigger ones are certainly going to cost more but will be able to search more deeply.

• User Interface. Is there a display? Knobs? A menu? The more expensive the model, the more bells and whistles there are on the display.

Metal detector accessories

Like any other hobby, having accessories in-store provides the opportunity for add-on sales. For example, all but the least-expensive models of metal detectors come with a 1/4 in. headphone jack. Experts advise the use of headphones, so as not to subject the general public to all the noises a detector can make. So, headphones are an easy upsale.

Another easy one, though it may take a trip or two out into the field to realize its value, is a pinpointer. While a metal detector indicates a general area, a pinpointer helps determine the exact location. That way the detectorist can quickly dig up a target and move on to the next section of ground.

Other accessories can include digging tools and even gold mining kits.

The metal detector—fun for all ages

Thanks to YouTube, those interested in the hobby can watch detectorists in action. This gives them a great understanding of how it all works. And thanks to the wide price range of metal detectors on the market, it’s easy to outfit someone with a detector they can afford.

If you’re looking for metal detectors to carry in your store, check out what Petra has to offer. As a distributor of Bounty Hunter metal detectors,  we carry models ideal for beginners as well as those with more field experience.

So, help others dig up the past and uncover lost loot—while making a tidy profit for yourself—with metal detectors!