1. DEPTH OF DETECTION
One of the main parametres of the metal detector is a depth of detection of objects. As a rule, for beginning this parametre it is covered by a gloom. It it is no wonder - in one catalogue advertising metal detectors you will not find instructions, on what distance the device finds out a coin, the metal jug, etc. Is underlined, at the best, the device and what time it how many weighs can work without accumulator change. The parametre "the maximum theoretically possible depth of detection" which several times is more than of what the person having control over the metal detector thinks is sometimes resulted.
To clear this point in question, the information stated more low, it is broken for convenience on a scale of the sizes of various subjects of search.
Coin
Let's begin with that the coin in diameter usually is meant a coin in descriptions of many foreign devices of 25 (mm). For those who else remembers, is a coin of the USSR advantage in 5 copecks. Depth of detection of such coin makes from 10 (sm) for frivolous devices to 50 (sm) for very serious. Depth of detection strongly depends on the size of the gauge (usually - diameter of a disk with coils). Roughly, for such coin depth of detection is approximately equal to diameter of the gauge. Smaller coins will be found out on smaller distances. For example, depth of detection of a coin advantage in 1 copeck will be approximately twice less, than is specified above for a five-copeck coin.
Bronze figurine, pistol
The metal detector finds out naturally, larger subjects on bolshem distance. To estimate this increase, usually cite as an example a bronze figurine or a pistol (as a relic from a Russian history it is possible to mention a gun kernel). Depth of detection of such subjects makes nearby 1 (). Depth of detection poorly depends on the size and on gauge type (it can be both with komplanarnymi coils, and with orthogonal on a bar). For the gauge with coils bolshego diameter and for the gauge with system of orthogonal coils on a bar depth of detection will be slightly more (on 20 % at transition from the disk gauge in diameter 20 (sm) to the gauge in diameter 30 (sm)).
Metal shit, bells
All told/in the previous paragraph fairly and for these objects, except for depth of detection which lies in a range 1,5-2,5 ().
The tank, steam locomotive, the plane
In serious language depth of detection of such objects is called: "the maximum theoretically possible depth of detection". Differently, there is a theoretical limit further which the electronic metal detector not in a condition to register objects basically, despite their as much as big sizes.
Existence of this limit on depth of detection is easily explainable if to recollect that the amplitude of the reflected signal inversely proportional 6-7й distance degrees, and depends on the size of object only in 3-5й degrees.
The size of maximum theoretically possible depth of detection makes from 1 () for the elementary devices with the disk gauge to 4 () for difficult devices with the big gauge of orthogonal coils on a bar. Unfortunately, this size usually appears in the advertising purposes, but on such depth you will not find anything!
REMEMBER!
The advanced electronic metal detector it is possible to find out an average coin on depth a maximum of 50 sm, a large massive all-metal subject - a maximum on 2,5 m.
SELECTIVITY ON METALS
Unlike depth of detection which rather modest values nesvedujushchy the person usually does not guess, selectivity on metals is represented clearer question - so many think. And they are mistaken.
As source of errors quite authentic advertising serves, as usual, not. In many catalogues and prospectuses of firms are resulted by close up of a photo of scales strelochnyh indicators of metal detectors. At once is evident that a device scale prograduirovana on sectors with instructions of a kind of metal: "iron", "not iron", "gold", "silver" etc. However, this graduation concerns, basically to small subjects and is unsuitable for distant search of large subjects.
The inconsistency of statements for high selectivity of metal detectors can be established even is purely speculative. Really, what will occur, if for experiment to try to define the metal detector with the selector on metals a target consisting of two small subjects - one of iron, another - from silver? Clearly that any indication of the indicator will appear false. Besides - depending on a parity of weights, the form and the sizes of these two subjects any result can turn out. For example, the arrow of the device can stop on sector "gold"! Metal detectors with selection on metals "confuse" iron subjects To the same ease with nonferrous, depending on their form and weight. Imagine sensations of the person which instead of the promised gold mountains finds out a scrap of a railway rail after excavation lasting many hours!!!
Summing up, it is possible to tell the following. Advertised possibilities of electronic metal detectors are exaggerated. Nevertheless, they remain till now a unique accessible class of the devices allowing "to see metal subjects through the earth".
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