Early metal detectors were developed at the tail end of the 19th century; however, many of these crude devices were unsuccessful in fulfilling their intended functions. Metal detectors as we know them today were developed in the 1920’s. Since that time, they have been used for a variety of purposes, including domestic, commercial and military purposes. The military uses metal detectors to locate bombs and mines, while commercial and government bodies use metal detectors to scan human bodies; however the use we often see depicted in cartoons and movies involves using them for archeology to uncover metal hidden in the ground.
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What Are The Working Components of a Metal Detector?
Most domestic metal detectors are made up of four key parts.
- Stabilizer – This keeps the unit steady as it is gently swayed from side to side, however this is not included in all models.
- Control box – This contains the majority of the working parts, including the speaker, the batteries, the circuitry and the controls.
- Shaft – This simply connects the control box with the search coil and it is often adjustable so that the user can set it to a comfortable height.
- Search coil – Also known as the antenna, the loop or the search head, this is the component that detects the metal.
Most metal detectors also include a jack port, enabling users to connect a set of headphones; helping the operator to listen more closely to any audible changes.
Operating a metal detector is relatively simple; however, learning to read the feedback and finding any ‘treasure’ that you may detect is a fine art. More advanced metal detectors have been designed to make this process much easier. Advanced domestic units will attempt to pinpoint the type of metal found and they will even estimate how deeply the metal is buried.
How Do Metal Detectors Work?
Metal detectors operate using one of three technologies. These technologies include BFO (Beat-Frequency Oscillation), PI (Pulse Indication) and VLF (Very Low Frequency). These technologies enable operators to detect metallic objects that would otherwise be hidden from view.
1. VLF (Very Low Frequency) Technology
Induction balance or VLF, is perhaps the most frequently used technology in domestic metal detectors. A VLF metal detector includes two separate coils that make up the search coil. The outer coil is the transmitter coil, and within this fixed loop is a coil of wire. The inner coil is the receiver coil, which also contains a loop of wire. These coils create an electromagnetic field, which is in turn bounced back off of any metallic object hidden in the ground. VLF metal detectors vary in price and features, however you can expect to pay between $50 and $100 online. The Bounty Hunter VLF 2.1 metal detector is a great VLF detector for amateurs, and it starts at around $77 online.
2. PI (Pulse Indication) Technology
Pulse Indication metal detectors are not as common as VLF detectors. Unlike VLF metal detectors, PI detectors can use single or multiple coils that send short but powerful bursts through the coils. Each burst generates a magnetic field and as the burst ends the magnetic field collapses, triggering a spike in electrical charge. This forces the next pulse to start, and so on. Typical PI detectors will send on average 100 pulses per second; however, units will vary from 20 to 1000 pulses per second. The Garrett Ace 150 metal detector costs around $150 and is an ideal tool for amateur treasure hunters.
3. BFO (Beat-Frequency Oscillator) Technology
Beat-Frequency Oscillator metal detectors are the most basic form of metal detectors available. One large coil resides in the search head and a smaller coil is hidden in the control box. Both coils are connected to an oscillator, which generates thousands of pulses every second. Unlike the PI and VLF detectors, BFO technology uses radio waves to detect metal instead of electromagnetic fields. These simple detectors are much cheaper than the other two technologies, yet they lack the level of control and accuracy offered by PI and VLF detectors. You may struggle to buy a BFO detector online, but there are ample instructions online on how to make one.
Metal Detectors for Kids
Little ones love the idea of taking a detector into the garden or the local woods to find hidden treasure, and you can even hide objects in the garden for them to find! For less than $50 you can introduce your children to the wonderful world of treasure hunting, with the Bounty Hunter BHJS Junior Metal Detector.This lightweight detector is a highly rated beginner’s tool, which is ideal for children aged five and over.
Other Metal Detecting Tools
As well as choosing a metal detector, you will also need to consider investing in other tools to help you unearth any treasures that you find. You should consider purchasing a strong but lightweight digging tool, and you may want to think about getting a carrying bag as well. You might also want to invest in a metal detecting book to help you better understand the art of treasure hunting.