· What is a metal detector?
· Who invented a metal detector?
· Where are metal detectors used?
· Types of metal detectors
· The art of metal detecting tips
· Common settings and terms available in metal detectors
What is a metal detector?
Metal detectors are electronic instruments which predict the presence of metals nearby. They help people find metal object buried underground or hidden within objects. They consist of a handheld unit and a sensor probe that is used to sweep over the ground. If the detector comes across a metal, it produces a tone.
A simple metal detector consist of an oscillator that produce an alternating current passing through a coil producing alternating magnetic fields here. If any electrically conductive metal get close to the coil, a currents is induced in the metal producing a magnetic field of its own.
lt’s important to know that metal detectors do not detect nonmetal materials such as pearls, bones, paper, gemstones or stone figures.
Who invented a metal detector?
The first metal detector was invented in 1881 by Alexander Graham Bell after the assassination of President James Garfield Alexander invented a crude metal detector in a bid to locate the bullet as the president lay dying. Although the detector did not help him save the president, it fueled the ambition to create a functional one.
Where are metal detectors used?
The first industrial metal detector was developed in 196os and were mainly used in mining and other industrial prospects.
Other uses include detection of land mines, detection of weapons such as guns and knives, archeology and treasure hunting. They can also be used to detect foreign materials in foods and in construction to detect presence of steel reinforcing bars in concrete and pipes buried in the floor.
Types of metal detectors
Walk through detectors
These are common in military installations and public buildings, security screening at courthouses, airports or prison access points They are simple to use as they only have two large coils and a handle and small speaker.
Hand carried detectors
These are small handles enough to be hand held. They are mostly used at security checkpoints. some units have been developed to be carried by pedestrians scanning for metal objects such as nails or landmines in the ground.
a gradiometer is used to measure gradient. Gradiometer metal detectors are walk though devices but are limited to detecting only ferromagnetic objects. They can also be mounted on police cars with the intent of detecting ferromagnetic weapons such as guns approaching the cars.
Magnetic imaging portals
Magnetic imaging is new technology in metal detection that uses radio frequency electromagnetic waves and displays the result of the scan on a screen. However, it does not produce a detailed image but only reveals the location and the approximate size.
The art of metal detecting tips
How you swing your metal detector is very important. If you swing your detector too fast, it will not pick smaller target because it did not have enough time to pick the disturbance in the ground. Additionally, if you swing the detector far off the ground, it will not pick deep targets especially if the detector is of high frequency.
Just like any other practice metal detecting is guided by laws and regulations. You cannot go metal detecting in private property without a permission National parks and states are off limit. Beaches, parks and schools are going to be dependent on local laws.
This may sound vague but digging is part of metal detecting. Use the right tools for digging and make sure to cover your hole appropriately. Minimize damage on the ground so that the area of digging can return to its original state quicker.
lt’s important to note that things that have been buried for long can be hard to detect since they are more likely to have corroded or oxidized
Before acquiring a metal, detector make sure that you know where it will be used as different metal detectors are used in different scenarios. Make sure to read detectors manuals carefully as understanding the proper settings, capabilities and technology used in metal your metal detector is the first important step towards metal detecting.
Below is a guide on some common settings and terms used in metal detectors:
This is the ability of a metal detector to distinguish between different targets. When doing a metal detecting exercise, you are likely to come across things such as rusty nails and battle caps. A metal detector should be able to differentiate between a bottle cap and a piece of copper so as to save on time digging up garbage.
Soil contain a certain level of metal such as iron. These metals can interfere with your detectors ability to detect coins and jewelry among other valuables in the soil. Ground balance enable the detector to bypass these materials. It's important to note that detectors come with several ground balance variations
Automatic: This allows for detection and adjustment for ground effects automatically
Preset: This is a predetermined level of ground balance by the manufacturer. The level works adequately in most environments
Manual: This variation allows for on-site adjustment by the user as per the changes in the ground condition.
Multiple: This allows the user to select either manual or automatic setting depending on their preference.
This is the best tool in a metal detector. It can distinguish between coins like nickel, penny, foil or the probability of gold. It then gives a high pitched audible tone for valuables and a low tone for junk. Frequently, the target ID is visual and is displayed on the LCD display screen.
Metal detectors frequency is the number of times a signal is transmitted and received by the detector every second. Most general purpose detectors operate with lower frequencies as lower frequencies scan go deeper giving out a better overall detection depth.
On the other side, high frequency detectors are more sensitive to gold and small objects however they are less able to penetrate deeper into the ground.
This is the ability of a detector to detect metal objects form a distance. This can be explained using a volume control example. If its set too low, it cannot be hard, but if it‘s set too high, the sound gets distorted. It is therefore necessary to lower detectors sensitivity to the recommended levels.
Search depth is the depth which a metal detector can search for metals. Lower frequency detectors go for deeper depth while high frequency detectors don't go deeper. Soil composition and search coil can also have an impact on search depth too. The larger the coil, the deeper it goes. You can mostly find coins to a depth of one and half times the search coil diameter. For example, if you are using an 8-inch search coil, you can typically find coins at 8 - 13 inches.