Have you decided to search for treasure or just black metal? Then you can't do without a good metal detector. How not to get confused in the variety of models and technologies? Let's figure out what to pay attention to when choosing.
Main features
In general, all metal detectors work on the same principle. They generate a magnetic field. Under its influence, metal objects begin to generate their own field. It is this that the metal detector is trying to catch.
The capabilities of different models differ. Some simply react to any metal they find. Others can even tell the difference between gold and silver. Before buying, it is worth studying the functionality so as not to overpay unnecessarily.
Metal detectors are usually used by security guards. It is these models that are used to check people at the entrance to various institutions. They are cheap, their functionality is minimal. The devices react to any nearby (5-15 cm) metal. Many models do not even have sensitivity adjustment.
Ground metal detectors are designed to search in the ground. The capabilities of different models can differ significantly. The key parameters here are selectivity and search depth. Budget models will only react to large pieces of metal. What kind of metal it is, you will find out only after excavations. Expensive models will be able to "spot" a small coin at a decent depth. And also - roughly determine what metal it is made of.
A pinpointer is usually used in conjunction with a ground metal detector. Let's say you came across a small coin with the help of a ground metal detector. You take a pile of clay out of the ground (say, 50 liters) and make sure that the coin is exactly in it. But where exactly? Without a pinpointer, you will have to manually sort out all the soil. But the pinpointer will show you exactly where to look.
Detection Method
VLF (Very Low Frequency). The method uses low-frequency (1-10 kHz) waves to detect metals. VLF metal detectors are the most common. They filter out "interesting" signals well, even if there is a lot of metal and metal-containing debris in the soil. Such models are ideal for searching for coins and rarities in populated areas. In the past, VLF metal detectors were completely analog. Today, most models use digital signal processing methods.
VFLEX. Minelab's development based on VLF technology. Both signal generation and echo processing are done digitally. This allows you to effectively get rid of noise, increases the sensitivity and selectivity of the device.
BBS, MULTI-IQ, FMF, FBS. All these are the names of similar technologies from different manufacturers. These metal detectors work in the same way as VLF/VFLEX, but on multiple frequencies at the same time. Different metals "respond" differently to magnetic fields of different frequencies. Therefore, such a metal detector allows you to effectively distinguish one metal from another.
PI (Pulse Induction). PI metal detectors do not emit a continuous wave. They send a short pulse and "listen" to the response. The method is effective in difficult conditions, when working on coasts, on wet or mineralized soil. PI models typically have a high search depth. This is a great option for archaeologists. But PI models are poorly suited for working in densely populated areas. They filter out different types of metals worse than VLF devices.
RF (Radio Frequency). Waves with a frequency of 50-500 kHz are used here. It is rarely used in modern metal detectors. Typically, the method is only found in deep search models.
Maximum Detection Depth
The parameter indicates the maximum depth at which the metal detector can detect an object. However, this only applies to large items. And in ideal soil: dry, not very mineralized, without unnecessary debris. To assess the real capabilities of the device, it is better to look at another parameter - the maximum depth of coin detection.
Maximum Coin Detection Depth
The parameter shows the maximum depth at which the device is able to find a small metal object the size of a coin. But coins are also different, so the characteristics should be taken with a margin. If this parameter is 15 cm, then the metal detector will notice a copper nickel at this depth. But the silver "scales" are unlikely.
Detection frequency
The operating frequency affects the depth and efficiency of the search. The lower the frequency, the greater the depth of the search. But at a low frequency, the sensitivity of the device decreases. Small objects may go unnoticed. In most modern instruments, it is possible to switch between several operating frequencies.
Low frequencies (3-5 kHz) are suitable for searching for large objects at medium to great depths.
Medium frequencies (6-8 kHz) are the most versatile for searching for most objects.
High frequencies (14-20 kHz) are suitable for searching for small objects at shallow depths. The thing is that they penetrate the ground a little worse.
Some models can operate on several frequencies at once. They have a higher chance of finding something valuable. They can detect both small and large objects at different depths. The higher the frequencies, the more versatile the metal detector. However, the price also increases.
Coil design
A monoloop coil consists of a single winding, which is the antenna for both the emitter and the receiver. Used on PI metal detectors and low-cost VLF models.
A concentric coil consists of two windings - internal and external. One is the antenna of the emitter, the other is the antenna of the receiver. This design increases the selectivity of the device. However, a concentric coil has a rather narrow cone-shaped detection zone. On the one hand, it is easier to find out the exact location of the find. On the other hand, productivity decreases. It takes a lot of time to inspect a large area with such a metal detector.
A DD coil consists of two D-shaped windings with their backs facing each other. The DD coil has a detection area in the form of a flat, wide "tongue". This design provides good localization accuracy. At the same time, in one pass, a DD coil "covers" a larger area than a concentric one.
Main functionality
Discriminator
The discriminator analyzes the characteristics of signals from different metals. It allows you to ignore metals that are "uninteresting" to the user. The main thing is to set it up correctly. A good discriminator can seriously speed up the search if there is a lot of different debris in the soil.
There are discriminators in almost all ground metal detectors. However, in budget models, they are inaccurate and inconsistent. The simplest discriminators are a sensitivity regulator. It screens out items with a response level below a certain threshold. Metal detectors with such a discriminator are suitable only for searching for ferrous metal.
More advanced models analyze not only the "loudness" of the response, but also other parameters. So, when using several frequencies, different metals "respond" differently. Analysis of these signals makes it possible to judge the size and material of the object more reliably. Some discriminators even calculate the target rating, which indicates the reliability of the metal determination.
It is convenient if the signal characteristics and target rating are displayed on the VDI screen (visual discrimination indicator). This gives a chance not to miss a valuable find, even if it did not pass the discriminator settings. For this, tone identification is needed: with it, the device emits a signal when metal is detected. The tone of the signal depends on the conductivity of the object found; It turns out that each metal emits its own tone. This allows you to quickly react to something interesting getting under the reel.
Ground balance
The quality of the signal largely depends on the ground. For example, dry sand is practically neutral — grains of sand do not respond to magnetic radiation. But particles of highly mineralized soil, when they get into the magnetic field, will begin to emit it themselves. False positives will occur. Simply reducing sensitivity is also not an option. This way you can easily miss something valuable.
Soil balance will help to deal with the problem. In inexpensive models, this option is not found. But in more expensive models, there are several balance options at once.
Manual. The mineralization value must be entered manually. It is set up on a section of soil under which there is no metal. You need to raise the reel 10-20 centimeters from the ground and slowly swing it up and down. Such a value of mineralization is selected at which false signals from the ground disappear on the VDI and in the headphones.
Automatic. It is adjusted in the same way - by rocking the coil up and down. However, you do not need to enter the value manually. Before balancing, you should enter the soil balance mode. The device will select the desired value itself.
Tracking mode. The device automatically monitors changes in the ground and adjusts settings in real time. This is convenient, but it can lead to errors in heavily littered areas. The device can take a signal from debris for high soil mineralization. Therefore, in many devices with a tracking mode, it can be turned off for a while.
Threshold Background (Threshold Tone)
This feature allows you to adjust the threshold tone, which is a constant background sound. At any signal under the coil, the threshold background is turned off. This happens even before the discriminator gives a signal about the detection. On clean ground, the threshold tone will allow you to find small objects that are not noticed by the discriminator.
Pin-point mode
In this mode, the detection radius is reduced to a few centimeters. This allows you to accurately determine the location of the target. If this mode in the metal detector works as it should, you can save on buying a pinpointer.
Additional features
Built-in speaker
Having detected metal, the devices usually give a sound signal. The built-in speaker allows you to hear these signals without connecting headphones.
Headphone Input
Most metal detectors are designed to connect headphones. Or they can switch between the built-in speaker and connected headphones. However, you can't connect headphones to some models. If you prefer silence, pay attention to this setting.
Armrest
A handy detail that helps keep the fixture in place while searching. If you have to search for a long time, the armrest is indispensable: it makes your hands much less tired.
Moisture-proof coil
If you plan to work near water, it is better to choose a model with a moisture-proof coil. Water ingress inside the coil will lead to breakage.
Nutrition
Different models of metal detectors can be powered by batteries or accumulators.
Battery models are convenient and economical. The main thing is not to forget about consumables and charge the battery on time. When choosing a battery model, pay attention to the charger and the number of batteries in the kit. Inexpensive metal detectors often have a small capacity. If they have a standard form factor, it is better to buy several spare ones at once.
Battery-powered metal detectors are less tethered to an outlet. You can collect an unlimited number of batteries for them. However, this is an additional cost. Also, pay attention to the type of batteries. Many models use elements of the "Crown" type. They are not so easy to find in rural areas, unlike the usual "fingers".
Options for choosing metal detectors
An inspection metal detector will be required for a personal search. And also to search for metal objects in clothes and bags.
Budget soil models are more toys than serious equipment. You should not count on any valuable finds using them. But why not find a coin in clean neutral soil? And they are inexpensive.
If you already have a ground metal detector, it may be a useful purchase to buy a pinpointer. It will save time when searching for small objects in the excavated soil.
If you want to try your hand at the search movement, you will need a simple, reliable device with a good detection depth.
If you dream of finding a treasure or at least a couple of gold chains on the beach, you will need a device that determines the metal of the discovered object with high accuracy (regardless of the conditions of use).
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