Metal detectors were previously used mainly for searching for mines and other munitions, but now anyone can use these devices to search for treasures or relics. Moreover, such detectors can be useful not only for hobbies but also as assistance in everyday situations – to find a lost piece of jewelry or any other metal object, to scan the ground before sowing or building a house, and so on.
Which metal detector to choose?
There are 3 main types of metal detectors: ground, underwater, or deep-seeking.
Ground metal detectors are the most common and come in a variety of functions and price categories – from models for beginners (with minimal settings) to professional ones (with complex differentiation). With a ground metal detector, you can monitor the soil for treasures, coins, and relics, including military ones. There are devices that can easily find metallic inclusions in the soil as small as fish scales! Many professional metal detectors have coils (search parts) that can be submerged in water, allowing for searches on the beach or by the river.
Underwater metal detectors (or Amphibians) – the name speaks for itself, they are designed for searching underwater, where the entire device is submerged, along with the control unit. Some quite expensive models even come with waterproof headphones included. Pay attention to the depth rating for searching when making a purchase!
Deep metal detectors are devices for searching large objects at depth, operating on the principle of signal transmission and reception. They can find, for example, a treasure chest with gold, or the outcrop of some ore, or old foundation rebar, etc. Such a machine will not be able to find small items. Features include being a rather heavy and bulky device, a large number of power elements, and a lack of fine adjustments.
Main indicators In complex devices, there are quite a few settings, but a novice treasure hunter needs to focus on the following:
Metal separation – the control unit has indicators for material recognition – silver, gold, copper, iron, etc.
Discrimination – that is, filtering out unnecessary targets and items. For example, signaling when finding a coin, rather than a rusty part.
Ground balance – needed to exclude the influence of soil on the search. It involves fixing the volume of soil under the search coil, after which the device subtracts this value from the overall indicators.
Search frequenciesIn modern models, frequencies of 3 kHz, 7 kHz, and 18 kHz are mainly used. There are also multi-frequency metal detectors, which are more versatile but are more expensive. Usually, three frequency ranges are distinguished:up to 10 kHz - low frequency, from 11 to 20 kHz - medium, above 20 kHz - high.
What is the depth of a metal detector with different frequencies? There is a rule: the higher the frequency, the better its sensitivity to small and thin objects (such as 'small coins'), as well as to low-conductivity metals like nickel, aluminum, etc. However, a high frequency penetrates the ground less effectively and works poorly with saline and mineralized soils. On the other hand, with a low frequency, the device is excellent at detecting larger items at depth, which is why such metal detectors are good for finding large treasures or military artifacts.
VDI indicators – what can be found with a metal detector
Almost any ground metal detector has a screen. Often, there is a VDI scale on it, which can help you understand what type of material/object has been found. (photo of the scale) Usually, this is a number within a certain range that describes the composition of the metal (alloy), the shape, and the size of the object. There is no universal scale; each manufacturer can make changes, so it is important to familiarize yourself with these indicators in the manual before making a purchase!
Example: iron – from 0 to 15, gold from 15 to 25, silver – from 25 to 35, or the Coin mode – iron from -95 to 0, and foil – from 0 to 5. Remember that different metals can give the same VDI number. See how the VDI number is determined using the Fisher F44 metal detector as an example.
Search Coils
A coil is the search component of the device, located at the bottom of the shaft (depth metal detectors may have slightly different designs). Modern types of coils are divided into 3 main types:
DD coil (Double-D) - this design uses 2 windings, resembling double letters D from the Latin alphabet - hence the name. This is the most modern universal option, creating a wide search area in the form of an even beam, making the search most effective and accurate.Concentric - in this case, the detection zone is cone-shaped and quite narrow, so the object is located more accurately, but such a search is not very effective over large areas.Mono-coil creates a wider search area, which is convenient for searching large territories, but this option is less accurate.
How does the device notify about detection?
Almost all models of modern metal detectors have a display for visual notification, where the aforementioned VDI scale is located, along with various information – for example, about battery life, icons (like a gold nugget), and other data. Familiarize yourself with the display of the device before purchasing, as each manual contains this description. Additionally, devices provide visual, vibrational, and auditory alerts (all of which can be customized). The sound indication can be multi-tonal, with the pitch of the signal indicating the type of detected object (gold, coin, trash, etc.). Different metal detectors can be paired with headphones – wired or wireless. There are models that connect to smartphones and transmit information to them, which also allows for adjustments through applications.
There are also army metal detectors – they are easy to operate and allow for quick finding of large metal objects over a wide area, the price of such devices is low, and even a non-professional can handle the settings. Among domestic manufacturers, FOMTECT and ZET should be highlighted.
Pinpointers
Besides metal detectors, you can find a variety of pinpointers. So what is this pinpointer and why is it needed by treasure hunters? Which pinpointer should you buy? Essentially, it is a small metal detector that locates the position of an object in the ground down to the millimeter!
This becomes very important if you have found a target with a regular metal detector, especially a small one that can be easily damaged when digging with a trowel. In this case, a pinpointer will come to the rescue: after removing some of the soil, the device is placed in this hole, and its tip determines the exact location of the object, allowing it to be extracted from the ground. Many pinpointers also come with a mini-trowel for digging, a flashlight, are waterproof for digging underwater (for example, at the bottom of a river), and can withstand falls from heights (they are shock-resistant). Additionally, modern models have adjustable sensitivity and response modes (sound, vibrate).
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