Everything You Never Knew & Need To Know About Metal Detectors
Metal detectors are one of the most interesting pieces of equipment that few know much about. At first glance, they seem to be mostly used by those seeking for something lost, buried treasure or personal. For some, it's a great chance to discover things that otherwise would go unnoticed.
For others, it’s a fantastic way to experience the world by finding clues that are left behind by others. The rewards from metal detecting can range from financial to personal entertainment.
In this post, we will offer the curious inquirer a thorough initiation into the unique world of metal detection. We will go into great detail about everything ranging from how metal detectors work, to the types of metal detectors, the top metal detector creators and more.
What Is A Metal Detector? – The Clue Is In The Name
A metal detector is an electronic device that detects metal. They are commonly used to find metal underground, underwater or to discover hidden metals as a security measure. Metal detectors are available in different kinds, but generally, can be divided into handheld and ‘stand-alone’ versions.
Hand-held versions are the ones typically used by hobbyist treasure hunters. The walk-through metal detectors at airports are a good example of stand-alone detectors. The ones that we will focus on mostly are going to be more portable and practical options. Without any further ado, let's go into the invention of the metal detector and beyond.
The Invention Of The Metal Detector
Early metal detectors were cumbersome machines that needed a lot of battery power, were very limited as to how much they could detect and were typically designed for use in mining. It wasn't until 1874 that a man named Gustave Trouvé invented a portable detector and the door to the world of metal detectors possibilities was opened.
In 1881, based on the work of Trouvé, Alexander Graham Bell developed a small handheld metal detector in an attempt to locate a bullet lodged in the body of James Garfield, 20th President of the United States of America.
Unfortunately, he was unsuccessful in locating the bullet (he failed to account for the metal springs in the president's mattress), Bell's detector became the prototype upon subsequent innovations rested.
In 1925 Gerhard Fisher was granted the first ever metal detector patent for his innovation which included adapted navigational systems. IN essence greatly increasing the accuracy of detectors.
Even though Fisher was the first to be granted a patent on a metal detector, it wasn’t until Charles Garret (founder of Garrett Metal Detectors) added his innovations in electrical engineering to eliminate oscillator drift in the early 1960s, that we start to see the rise of the modern metal detector.
How Metal Detectors Work
While the advancements in metal detector technology have provided us with different methods of detecting metal, the oldest and still most common type of detectors relies on the relationship between electricity and magnetism to find metals.
If you've ever made an electromagnet by wrapping a coil of wire around a nail and hooking it up to a battery, you know that magnetism and electricity go hand in hand.
Detecting metal with a metal detector starts with a Transmitter Coil. Basically, a coil of wire through which electricity flows. The electricity flowing through the wires create a magnetic field.
As the detector comes within range of metal, this magnetic field affects the atoms in the metal, which in turn creates an electrical activity in the metal.
The electrical activity created in the metal, in turn, creates a secondary magnetic field, this time around the metal. This second magnetic field is the one the detector ‘detects' with the Receiver Coil. This Receiver Coil is connected to a loudspeaker, and as it detects the second magnetic field, it triggers the loudspeaker to beep or clicks.
The Anatomy Of A Metal Detector
A basic metal detector consists of a brace or handles for the operator's arm with a Control Box (circuitry, microprocessor, controls, speaker, and battery) connected to the shaft on one end.
The Shaft, in turn, connects the brace and control box to the coil and allows the operator to sweep the coil close to the ground without having to bend over. An insulated wire extends from the control box and wraps around the shaft towards the coil.
Some detectors have a Stabilizer, which keeps the device steady while the operator sweeps the coil back and forth.
The Coil or Search Head, Loop or Antenna is the part of the metal detector that sweeps close to the ground and does the detecting.
The Technology Behind Detecting Metal
All metal detectors use the following technologies:
Very Low Frequency (VLF) Detectors
VLF Technology (also known as induction balance) is the most common type of metal detection and depends on the interaction of electricity and magnetism between a Transmitter Coil, a metal object, and the Receiver Coil.
Thanks to the advancements in technology, most VLF devices come with an integrated circuitry and small computers which process the information in the Receiver Coil and displays that information on the control box.
Since different metals have different levels of conductivity and thus affect the magnetic field in different ways, the computers in the control box can usually detect the type of metal found as well as the approximate depth at which it is found.
Pulse Induction (PI) Detectors
The PI induction technology relies, as the name indicates, on a pulse rather than on electric fields. Short pulses or bursts of current are sent through a single coil. This current creates a brief, outward radiating magnetic field.
When the pulse or burst or current ends, the magnetic field collapses very suddenly, creating a sharp electrical spike. This spikes last only a couple or microseconds and cause a next pulse to run though the coil.
If the magnetic field comes in contact with a metal, this metal will interfere with the speed at which the magnetic field collapses. The processing computer can determine, based on this information, if the field has been interfered by a metal object. While it can’t tell what type of metal object is found, PI Technology does better at finding metal in soil with high conductivity or in salty water.
Beat-Frequency Oscillation (BFO) Detectors
The BFO Technology is similar to the VLF technology, but in this case, both coils are connected to an oscillator and generate electrical pulses that are slightly offset from each other. As the electrical pulses travel through the coils, they create radio waves.
The processor then creates a set of tones or beats based on the different frequencies. This technology is easy to manufacture and BFO Metal Detectors are therefore a lot cheaper than other types. However, they are a lot less accurate and cannot distinguish between metals.
Types Of Metal Detectors
Different detectors are configured for different kinds of searching and take all different conditions such as the size and type of metal searched for, the makeup of the "ground," possible interference from other objects, and whether or not the detector is meant to be used in or around water into account.
Here is a list of most common types of metal detectors and the features that are most desirable in each one:
Type Of Metal Detector
General and versatile searching for a variety of metal objects
Usually, a low entry investment allowing general exploration. High-end models offer high performance in a variety of situations.
Coin & Relic Detectors
Useful for searching medium- to small-sized coins in areas that are littered
Use VLF technology
Tend to be very sensitive
The lower operating frequency aid in the detection of man-made and manufactured objects
Used for searching smaller deposits of naturally occurring gold
Use VLF technology with smaller coils.
Specially designed for searching metal on beaches and under water
Waterproof to depths up to 200-feet.
Use PI Technology, which is helpful in aiding the performance of metal detecting in salty water.
Searching for concealed metals in luggage and on persons
Operates on standard electromagnetism principles.
The most widely-used example of an industrial detector is the doorframe detector, used in the security at airports.
Specifications – Turning The Dials
Most middle and high-range detectors will come with a range of dials, knobs, and buttons allowing the operator to set the ‘detecting specifications' to his or her preferences. While the variety of specifications and settings will differ per model and brand, in general, there are three main areas open to adjustment: Sensitivity levels, Discrimination Modes, and Ground Balance.
The sensitivity levels on your metal detector determine the ability of the detector to bleep or click at the weakest or strongest fields received. Setting the sensitivity level high will not let the detector find more, just let you hear more. If you are working on a soil with high conductivity, a higher level of sensitivity will let you hear lots of additional "noise."
Most metal detectors come with discrimination modes, commonly:
As the name implies, this mode has the widest range of detection capability. All sorts of different metals can be detected, including iron, steel, aluminum, silver, copper, and gold.
Full-discrimination mode usually can be controlled to increase the level of discrimination and will automatically exclude trash from being detected.
Tone Discriminate Mode
In Tone Discrimination mode, the detector will reject iron and emit a different tone for different types of metals. This mode is most useful when hunting for treasures in a highly littered area.
Some newer models of metal detectors come with a pinpoint mode. This mode helps the operator pinpoint the location of the detected metal. This is especially useful when searching in areas where there is a high concentration of undesirable items and for beginner hunters.
Ground balancing a metal detector is like setting the scale to zero so that it ignores anything with similar conductivity to the soil. Your detector can come with either of the following ground balance options:
Preset Ground Balance
A preset ground balance means that the detector has been adjusted to a particular set range covering varying types of soil and environments. This the most general setting and will work well enough under general conditions but will give you false or incomplete readings on soils with higher mineralization.
Auto Ground Balance
Detectors with an Auto Ground Balance can sense and adjust to different mineralization levels in the soil. This is obviously a much more accurate balance than the Preset Ground Balance and will be very convenient for most hunters.
Manual Ground Balance
Manual Ground Balance offers the most accurate results because it can manually be set and adjusted to the specific area where the searching will take place. While doing this correctly requires some practice, the Manual Ground Balance option is a helpful tool to have
Using A Metal Detector
Using a metal detector is not as simple as turning it on, swinging it around and magically finding treasure. To effectively use your detector you must read the manual and go for a couple of practice runs in the yard before going out into the world.
While you might not become a metal detecting pro overnight, with dedication and proper use of your detector and some practice you will have lots of interesting things to find all around you.
Here are a couple of tips to get you started:
Read The Manual
Do not skip this part. You must become familiar with the different parts of your metal detector and the proper use of each one.
Practice Makes Perfect
Run your detector over different items, like a pull tab from a can, a nail, a coin, etc. and become familiar with the different sounds your detector makes. Practice sweeping the coil in a different direction and become familiar with the range of motion.
Search In A Pattern
When it comes to using your metal detector to hunt for treasure, there is no substitute for working methodically. A proper pattern will help you keep track of the area covered and the ground that still needs to be searched.
Get The Target Out Of The Ground
If you have dug up something less than a treasure, say a piece of foil, do not throw it back in the ground. Chances are you will detect it again later and end up digging twice for a piece of trash.
Don't Clean The Artifacts
Under no circumstance should you clean your found treasure with anything other than water. Brush off excess dirt with a soft brush, gently rinse it with water and pat dry. If you still can´t tell what it is or how much it is worth, take it to a professional.
Many make the mistake of trying to clean it off with a bit of soap or vinegar. Depending on the material your find is made of, this can corrode its surface and make it worthless as quickly as you found it.
Not only will they keep other people from bothering you, but they will also help you hear the bleeps and clicks of your detector without interference from wind, traffic and other exterior noises. Only by paying attention to the audio output as well as the readings output from your metal detector will you be able to catch every detail about any potential valuable finds.
Proper Cleaning And Storing Of Metal Detectors
Luckily, metal detectors don´t usually require a lot of maintenance. Just keep in mind that is has metal and electric parts, so it´s important to keep it clean and to store it dry.
Wipe down the coil and shaft of your detector with a damp cloth after every hunt, or every time dirt or soil has gotten on them. Remember that the control box is usually not waterproof, so it´s best to clean this area with a dry cloth.
If you get caught in a rainstorm or are searching in damp conditions, make sure to remove all your control box covers to allow the unit to dry out completely before storing it.
It is best to store your detector in a cool, dry place and always to remove the batteries from the control box. This will prevent them from emptying too quickly or worse, leaking.
Metal Detector Manufacturers To Look For
When you are just starting out you might be tempted to opt for cheaper no-name brand metal detectors. Unfortunately, the rate of treasures found is directly related to the quality or your detector.
This is why you should invest in the best quality metal detector you can find. Established brands have years of experience in making metal detectors and offer a wide range of models and options to choose from.
Bounty Hunter Metal Detectors
"Bounty Hunter," is the industry leader in hobby detectors, offers an "exclusive 5-year warranty` and is known to have ´feature rich´ models in different price ranges. If you are just starting out, you should check them out.
Garrett Metal Detectors
Garret Metal Detectors also some from a long line of manufacturing that is embedded in American society. In fact, Garrett Detectors are all exclusively manufactured in the United States. Ensuring a high level of quality control. In fact, Garrett was the Official Metal Detectors Supplier for the 2015 Pan Am Games in Toronto, Canada.
Fisher Labs Metal Detectors
That´s right; Fisher Labs was originally founded by Gerhard Fisher, first to receive a patent for the metal detector. Obviously, they have been in the metal detector business for a long time. Fisher Labs manufactures a wide range of detectors, from hobbyist to security grade equipment.
They pride themselves in offering the industries' best ergonomics and most streamlines user interfaces. Also important, their ground balancing capabilities are said to be revolutionary. An option for a serious treasure hunter.
Minelab Metal Detectors
Minelab prides itself in being the top supplier of not only consumers but also humanitarian demining and military detectors. Minelab focuses on hand-held metal detectors. The humanitarian and military involvement of this company can make your metal detector purchase a morally based one.
Metal Detecting is more complicated than it may first appear. Few get the chance to enjoy it, either because of a lack of time or a lack of understanding. There is nothing more disappointing than trying to undertake a new hobby and failing, which leads to wasted time, energy, and money.
Metal Detection is one of the few hobbies where your equipment truly matters in terms of how much fun you can actually have. If it's something more than a hobby, then your metal detection equipment ends up being the basis of your livelihood, and the last thing you want to do is risk your livelihood by not getting the best tools you can afford.
Metal detecting is an exciting craft with a long history, but it’s much like learning to ride a bike. The more inexperienced you are are more help you will need and the more general your equipment will be.
As you gain experience you will better understand how to best use your metal detector and also what features are best for you and the types of searching you want to do. Do your research, buy the best metal detector for your specific needs and keep practicing.
If you are interested in finding out more about which metal detectors are really worth the price and which are perfect for specific types of scavenging adventures, consider checking out our equally thorough buying guide. It is the perfect resource for discovering which metal detectors are great for what, and which are best to avoid, all in one easy to read and saveable form!
Do you have any questions? What has been your experience using metal detectors? Share your comments or stories in the section below!