A metal detector is an electronic device that is used to detect the presence of metal nearby. It is used mainly to find hidden metallic treasures, arms or mines buried underground. In the present day, metal detectors are used mainly for security purposes at the entrance or exit of buildings. This instrument has been used for security, archaeology, geophysical prospecting, and detection of foreign metallic material in food which can turn out to be toxic.
The history of metal detectors
The metal detector was invented back in the 1800s, after the advent of electricity. Alexander Graham Bell, during 1881, was hired to invent a device to locate a bullet in President James Garfield who was shot in Washington on the 2nd of July. However, the first metal detector made by graham was not able to locate the bullet because the springs of the bed, on which the patient lied, messed up with the readings. Sadly, even though Garfield survived the bullet hit, he died from an infection that infected his wound.
Moving on into the 1900s, a research engineer named Gerhard Fischer, also the founder of Fisher Metal Detectors, was studying aircraft radio detection finders. When he came across a problem of metallic ores distorting the navigational systems, this led him to share an idea about portable metal detector with Albert Einstein, which eventually got patented in 1925.
The metal detector continued through the developmental phase at Fischer. However, Charles Garret, the founder of Garrett Metal Detectors, played a significant role in the development of the metal detectors during the 1960s. Garrett, who had taken up metal detection as a hobby, saw the failures of the detectors that existed at that time. So, he decided to make his own from scratch. He invented his personal with better search coils and oscillator drift, which he got granted a patent for.
The initial design of the device was extensive in size, but as the times progressed, metal detectors started being manufactured in various sizes. The concept behind the invention remained the same across centuries.
Types of metal detectors
There are three different types of metal detectors, namely, Beat Frequency Oscillation, Very Low Frequency, and Pulse Induction Detectors. It’s best to understand the different types and recognize which one suits you the best before purchasing one.
Beat Frequency Oscillation:
It is one of the most commonly found metal detectors. It can easily be found at an electrical store. This particular detector is considered primary and weak as compared to the other alternatives available. Just like all the other metal detectors, the Beat Frequency Oscillation detector consists of a copper coil rolled around a ring made of iron or steel. There are two rings, a larger one installed at the base while the smaller one is attached slightly above the other ring. Both the coils are connected to the oscillator for frequency generation.
Both these coils, however, work separately at a different frequency. The metal detector detects the difference in the frequency of both the coils and a pulse of a radio wave is generated, which is received through a speaker attached to the device. Metal detectors also come with headphones, that can be used to hear the beeping sound in the presence of metal nearby. Thus, when the base coil is placed near a metallic object, it distorts the stable hum being created by the presence of electromagnetism between the coils. This interference in the frequency transmission indicates the presence of a metallic object.
The simplicity of this device makes it a cheap option. Despite low accuracy, it can be considered an excellent device for beginner level metal detection. Best frequency oscillation is capable of locating objects at a distance of 2 feet under the ground.
Very Low-Frequency Detectors
This one is currently the most popular among the metal detector users or experienced treasure seekers. Very-low Frequency Detectors offer greater accuracy and sensitivity. The detector consists of two spherical coils as well, where the first one works as a transmitter while the second one works as a receiver. Strong electric current, produced through the transmitter, is received by the receiver which amplifies them.
Consequently, a magnetic field is created around the coils, which extends about two feet underground. As soon as it comes across a metallic object, the object gets charged too and produces a magnetic field around itself. This magnetic current then interferes with the magnetic field of the coils, and the secondary coil picks the disturbance and sent to the audio system through which the user can hear it.
This metal detector can distinguish between different metals by generating varying frequencies. A stronger field is produced in the presence of steel or iron, which these detectors can differentiate from other metals. This helps in saving up time one would have wasted in digging up a useless piece of junk. Furthermore, due to its high sensitivity, it can sense objects that have a feeble magnetic pulse. Such metals include gold, which is extremely valuable. This is why this type of detector is a better choice when it comes to searching for valuables.
Pulse Induction
Pulse Induction detector is the latest technology when it comes to metal detectors. This type is used for security purposes for the detection of any concealed weapons. This device employs echolocation. It can consist of one or numerous coils that work collectively. It sends short bursts of powerful current through the coils, however, as soon as this current end the magnetic field reverses. The presence of any metallic object is detected as soon they come under the influence of the magnetic field. The pulsating model helps to identify fields created by itself. This helps filter out the noise of the other objects that might help a preexisting magnetic field.
Despite being a perfect detector, Pulse induction detector cannot distinguish between different types of metals as low-frequency detectors can do.
Most of the information needed for making a sound decision for buying a metal detector is presented above. If you still have any queries, you can always contact us and we will be happy to help!