How to choose a metal detector?
Before you arm yourself with a metal detector, you need to decide what exactly needs to be found and where. A metal detector (aka metal detector) is a device for searching for metal objects wherever they are (at construction sites, in the ground, in water and under water, during a personal search). The metal detector has the function of simply detecting the presence of a metal object in a particular environment. A metal detector not only detects a target, but also classifies what material it consists of - non-magnetic or ferromagnetic, that is, it gives out the so-called metal discrimination. Metal detectors are divided into several main groups, let's consider them in a similar way.
Simple ground metal detectors
Starter devices have a minimum of features when searching. One or two frequencies are used to search for a target. There is a possibility of including discrimination, sometimes determining the depth of the object. The search depth limits for such metal detectors are not very large and depend on the quality of the soil. For example, "scales" (coins of the 15th-17th centuries) - 3-5, a five-kopeck coin (the time of Catherine II) - 15-20, an ax - 20-30, a hatch cover - 70 centimeters.
There are, of course, craftsmen who find schemes for metal detectors in the literature and try to assemble them on their own. However, the quality of such a device leaves much to be desired. At home, it is unlikely to protect the metal detector from extraneous electromagnetic interference when setting up, even if there is special equipment for this. The background generated by innumerable household metal objects creates a lot of interference. As a result, in field tests, the metal detector starts to give erroneous readings.
Of course, at home, nevertheless, you can assemble an elementary metal detector with sound indication, however, in the field "black" large target will still give out a "color" signal. It is very difficult to protect metal detectors from such interference without a hodograph (special signal visualization unit). And the depth of detection with homemade metal detectors is very small. Even the first industrial metal detectors found a coin that was only at a depth of no more than ten centimeters. The question arises about the effectiveness of the use of such metal detectors. The answer is simple - luck brings positive results in 90 percent of cases, and only 10 percent falls on the quality of the metal detector. Many facts are known when the simplest metal detector was ahead of even the professional one in terms of the number of finds.
Semi-professional metal detectors
These are devices for people with sufficient search skills. The operation of such metal detectors is based on the principle of multifrequency radiation. Such metal detectors make it possible to operate not only audio, but also visual information. This information is displayed on the screen where you can see the VDI (conductivity index) of the detected target. The VDI value in the positive zone is "+" and it indicates that the detector has detected a non-ferrous metal, and a negative value is a black (magnetic) metal. By the value of this index, it is possible to determine, with an accuracy of 70 percent, which particular “colored” target has been detected.
For example, copper and silver coins produce a VDI index close to the maximum. On different models of metal detectors, the digital values of the VDI index (min./max.) Are different: some from 10 (-) to 100 (+), others from 30 (-) to 50 (+), and so on. That is why these metal detectors are classified as semi-professional. Available detection depth for them: "scales" - 5-15, five-kopeck coin (the time of Catherine II) - 25-30, ax - 40-50, sewer cover - 100-150 centimeters.
Professional ground metal detectors
Their cost can reach several thousand dollars. Why? Because a professional metal detector is designed for specially trained prospectors. It has built-in discrimination with differentiated sound, multi-frequency search gamut, there are various manual and auto settings.
Professional ground metal detectorsProfessional devices detect the presence of a “colored” target near a “black” target with an accuracy of 80 percent. This enables a more accurate search in places of accumulation of household iron waste. Metal detectors use digital visual and audible alarms. Automatic analysis of readings allows the user to understand what exactly he found, as well as the depth of the find and its size.
The analysis of digital signals in such devices is assigned to the microprocessor. It can be argued that such a device is, in fact, a search computer with great capabilities. For example, the detection depth of professional metal detectors: "scales" - 15-25, a five-kopeck coin (the time of Catherine II) - 30-45, an ax - 50-80, a sewer cover - 150-200 centimeters.
Metal detectors for gold prospecting
In practice, the entire line of such metal detectors is classified as professional. They have a frequency to detect even the smallest gold grade. This noble metal has a characteristic VDI, similar to the foil index in both audio and visual discrimination. Filtering foil signals with gold signals is extremely difficult. But it is even more difficult to find a grain of gold in the ground. Therefore, gold prospecting devices distinguish this frequency from the frequencies of other targets, while the search data for other objects remains at a high level.
Underwater metal detectors
The options for underwater metal detectors are designed with interference in mind depending on the salinity of the water. Devices for underwater search are used to study the bottom of water bodies in the coastal zone, beaches. They have a device body and headphones isolated from water ingress, and there are also many settings for searching in various environments. Underwater metal detectors only emit audio signals. The depth of detection for these devices is entirely dependent on the search environment.
Depth metal detectors
This is already quite solid search equipment for highly specialized purposes. Depending on the model, it can locate a hoard of coins buried at a depth of two and a half meters, and such large objects as large metal structures, pipelines at a depth of six meters. However, deep metal detectors have disadvantages, because they are designed to detect only volumetric targets and cannot respond to a coin lying at a depth of five centimeters. These metal detectors do not have a discrimination function, which means that when an object is found, you will have to dig it out to determine what exactly was found. Devices of this kind are usually used during excavations in areas of former hostilities. Deep metal detectors (aka locators) are widely used by engineering services to work with underground utilities. With their help, specialists can calculate, with an accuracy of a centimeter, where an object is located, in which direction it extends, and much more.
Hand-held inspection metal detectors
Devices for searching for metal objects during body searches are called hand-held metal detectors. They are widely used by security and protection services, customs, police, military. They react to an object the size of a pin. If, for example, there is a metal spring in a plastic ballpoint pen, then the detector will definitely signal. A security screening metal detector has already become an obligatory attribute of law enforcement agencies.
Arched (frame) stationary metal detectors
An arched stationary metal detector is mounted on a fixed base and is designed to detect metal objects from a person passing through it. Such devices are installed at train stations, airports, at checkpoints of enterprises and institutions, when organizing large-scale actions, etc.
If you are a beginner, then your first purchase should definitely be the simplest metal detector, after you gain experience with this device, you can move on to more professional models.