10 Best Metal Detectors | March 2017
- visual reference of detected metal
- touchpad controls
- four preset search modes
- lightweight enough for all-day use
- only requires 4 aa batteries
- no backlighting on the display
- detects small items to 8 inches deep
- loud speaker for headphone-free use
- distinct high detection tones
- high gold sensitivity
- pulse indication detection
- neutrally buoyant 12-inch coil
- submersible for underwater use
- multiple stem configuration options
- includes headphones
|Brand||Garrett Sea Hunter MK-I|
- numeric display distinguishes metals
- high sensitivity response
- provides a depth measurement
- 10 turn-on-and-go hunting programs
- works with wireless headphones
- onboard quick reference guide
One Man's Trash Is Another's Treasure
If you spend a lot of time at the beach, then you've probably come across those people with long, stick-like instruments examining the sand. If you have any interest in treasure hunting, then you may consider yourself among the beachcomber elite looking for the next big find by the sea. If you've ever been stopped by airport security, then you're probably aware of the use of metal detectors in at least some form. Regardless of the situation, the ability to detect metal is an important function in society from a hobby, research, and safety perspective.
Metal detectors are most useful for finding metallic inclusions hidden inside objects made from other materials and for finding objects buried deep underground that cannot be detected with the naked eye. A typical metal detector is a lightweight, handheld device with several parts that include a stabilizer, control box, shaft, and a search coil. Most detectors also have a headphone jack for listening to the device's audible beep alerts when it finds something. The stabilizer keeps the detector steady as you sweep its search coil back and forth over the ground.
The control box contains all of the detector's internal circuitry, controls, its speaker, and microprocessor. The search coil detects the metal and it is connected to both the shaft and control box. The shaft is often adjustable to accommodate different user heights. Once the unit is powered on, the user simply waves the search coil back and forth over the ground. When the coil passes over a target object, an audible signal occurs. The closer the detector is to the piece of target metal, the higher the signal tone will be in the speaker or headphones.
While metal detectors can utilize several types of technology to operate, the most popular method is very low frequency (VLF) technology. A metal detector using very low frequency leverages both a transmitter and receiver coil. The transmitter contains a coil of electric wire through which a current is sent in one direction and then another. This directional change occurs thousands of times per second. The number of times a current switches directions in one second determines the metal detector's frequency. The receiver consists of another coil of electric wire that acts as an antenna used to both pick up and amplify frequencies originating from objects buried underground. The electric current running through the detector's transmitter coil generates an electromagnetic field.
Whenever the current changes direction, so does the polarity of the magnetic field. The magnetic field from the transmitter coil continues to push down into the ground and back out again. While this occurs, the field interacts with any conductive objects it encounters underground, allowing those objects to generate their own magnetic fields. When underground objects emit these magnetic fields, the receiver coil picks up the interference they produce and transmits it directly to the detector's audio system where it is picked up by the user (through a speaker or headphones).
A Full Range Of Choice
Context matters in one's decision to invest in a metal detector. From an archaeological perspective, the device allows researchers to find and preserve historical artifacts at sites that would otherwise be extremely difficult to detect. That said, if you're a scientist with a passion for history, then finding the most cutting-edge metal detector will be important.
Some of the best detectors include high-definition color screens and the ability to pick up multiple frequencies. If one prefers the freedom of movement without extra cords, then a metal detector with the ability to interface with wireless headphones is another important feature to consider.
Some metal detectors are even submersible up to one hundred feet for underwater use, so if you snorkel or consider yourself a recreational diver and wish to go treasure hunting in the ocean, durability and a waterproof design will come in handy.
The larger the search coil, the easier it can be to find what you're looking for. Many detectors offer search coils between eight and twelve inches in diameter, which allows you to cover a large search area more quickly.
A Brief History Of Metal Detectors
The invention and popularity of the metal detector took shape during the latter part of the nineteenth century around the same time major strides were being made in the field of electrical engineering, thanks to figures like Alexander Graham Bell and Thomas Edison among others. By the mid-1800s, scientists, scholars, and gold miners began experimenting with machines that could locate metal underground. In 1874, a Parisian inventor named Gustave Trouvé invented a handheld device for locating and extracting metal objects (e.g. bullets) from patients.
Inspired by Gustave Trouvé, Alexander Graham Bell devised one of the first dedicated uses of a metal detector in his efforts to locate the bullet responsible for killing United States' twentieth President James A. Garfield in Washington D.C. in 1881. Garfield was shot in the back by American writer and lawyer Charles J. Guiteau. While Bell's metal detector functioned properly, it was unable to locate the lodged bullet due to the interference caused by the metal coil springs in Garfield's bed. Although Bell's invention could not save Garfield, his invention became the prototype from which all future metal detectors would be constructed.
The first metal detectors of the twentieth century were large, difficult to use, and operated through the use of vacuum tubes. Many of these detectors were later used in Europe to discover undetonated bombs and landmines after World War One and Two.
In 1925, Gerhard Fisher was granted a patent for the first portable metal detector following his discovery that radio beams were being distorted by local ore-bearing rocks while studying navigation systems. Fisher sold his first device to the general public in 1931. Between the 1950s and present day, detector technology has continued to be refined and improved, thanks largely to detector enthusiasts, hobbyists, and scientists adding the use of transistors, discriminators, improved search coils, and wireless technology to make metal detection easier than ever before.