Metal detectors: installation, setup, operation.
METAL DETECTORS: INSTALLATION, SETUP, OPERATION
When choosing arch metal detectors (AMD), consumers are primarily interested in the technical and operational parameters of a particular model. This raises many questions — from the most general and elementary to quite complex ones, concerning very specific areas of their application. In the article prepared by the manager of the Metorex company G. A. SINELSHCHIKOV, you will find answers to the most frequently asked questions about AMD, which may be of interest to a fairly wide audience of users. (See also SBST No. 4, 5, 1996)
What does a metal detector react to, besides the mass of the metal object being carried?
The more metal passes through the arch, the easier it is to detect. However, for detection purposes, the shape and surface area of the metal object are no less important than the amount of metal. The easiest way to explain this is with the following example. Take a sheet of aluminum foil and cut it in half. Next, roll one half of the sheet into a ball and leave the other half flat. The half of the sheet that remains flat naturally has a larger surface area than the ball, and therefore will be easier to detect. The ball has the same weight, but because of the smaller surface area, a higher sensitivity setting will be required to achieve the same detection characteristics. Obviously, the signal from an aluminum Coca-Cola can will be comparable to the signal from a small pistol, and an object shaped like a rod (a knife, a piece of rebar, etc.) will be comparable to a small pistol. most difficult to detect with an arched metal detector.
Is it possible to make AMD detect weapons and not react to, say, keys?
The answer to this question is one of the main ones in developing advanced AMD. Indeed, both the gun and the keys are made of metal, and at first glance, the task of separating them is quite complicated if we operate only with the sizes of these objects, which in some cases can be comparable. Upon closer examination of the behavior of various metal objects in an induced electromagnetic (EM) field, it is possible to discover that different types of metals produce different levels of signals, i.e., values of the intensity of the secondary EM field they create. For example, ferrous metals, such as magnetic steel and iron, have high signal levels and are the easiest to detect.
Non-ferrous metals (gold, silver, aluminum, lead, and stainless steel) produce significantly lower signals and require a higher sensitivity setting to achieve the same detection results. Thus, if you select the minimum sensitivity value required to detect a gun made of gun steel, the probability of detecting objects made of non-ferrous metals (keys, coins, pens with a metal body) will be quite small. However, if the total mass of non-ferrous metal objects is greater than the mass of an object made of gun steel, then relying only on the difference in sensitivity is not always justified.
What are the more than twenty programs in METOR metal detectors for?
The programs in METOR metal detectors are, in fact, algorithms for analyzing and processing signals that are constantly present in the electronic circuits of the AMD and that arise there when a metal object is brought into the arch opening. As was said earlier, different metals behave differently in an electromagnetic field. This is manifested not only in the amplitude of the secondary electromagnetic field, but also in its change over time. The difference in the amplitudes of signals from iron and aluminum, for example, a few milliseconds after the excitation pulse (all METOR metal detectors use the pulse principle of excitation of the electromagnetic field) is much more pronounced than immediately after it. This means that using different time delays of the analyzing pulse, you can get much more information about the nature of the metal carried through the AMD.
Graphs of reactions of various metals to external electromagnetic field were obtained experimentally and measurement points were selected for detection of different materials by one metal detector. AMD METOR programs contain all data on processing signals coming to the receiving unit of the metal detector from objects made of different types of metals. All that remains is to select the one suitable for a specific application. It is worth paying attention to the fact that in some cases the greatest difference in signal amplitudes is manifested at the moments when their absolute values are small, which means the influence of «parasitic» noise is great. High selectivity by materials (the ability to distinguish different types of metals) is often accompanied by lower resistance to external noise. And therefore these factors should be taken into account when choosing a program. The AMD METOR operating instructions provide recommendations for using certain programs in various conditions.
Is it possible to configure the metal detector so that it reliably identifies combat weapons and does not react to a gas pistol?
If the gas pistol is made of aluminum or another non-magnetic alloy, and the combat weapon is a Makarov pistol, then, given all of the above, such a possibility exists. However, wouldn't such a metal detector setting be a mistake? If we consider what models of hand weapons are used in terrorist attacks, we can find certain types of pistols and revolvers, both made of non-magnetic alloys and not exceeding half a palm in size. Therefore, having set the AMD to PM, we most likely will not notice, for example, a five-shot MINI revolver of 0.22 caliber, which is made of stainless steel, weighs 130 g and has dimensions of 100 x 59 x 20 mm. Of course, we can say that such weapons are rare in Russia, but with a great desire and money, many people can become owners of such a miracle. There are fewer problems with obtaining a gas pistol, converted to fire live ammunition, which AMD, configured according to the proposed principle, also «will not see».
The proposed location for installing the metal detector is very «heavy» — metal-reinforced concrete walls, in the immediate vicinity — airlock doors, power wiring, etc. Will the metal detector work in such conditions?
It is difficult to give a clear answer to this question. METOR metal detectors operate without deterioration of their characteristics at distances of 10 cm from stationary metals (reinforced walls, metal railings, gratings, etc.) and 50 cm from moving metal objects (doors, large glass surfaces in metal frames (due to their constant vibration), moving elements of turnstiles, etc.). Taking into account all the factors affecting the operation of the metal detector, in most cases it is possible to place the AMD in a complex environment.
In some cases, this is achieved by accurately determining the location of the AMD, selecting a program for analyzing the measurement results, and accurately adjusting the sensitivity. Sometimes it is necessary to install special protective panels that reduce the impact of moving objects, and to temporarily block the AMD — special inputs are provided for this. To protect against the impact of strong electromagnetic fields, it is sometimes necessary to change the excitation frequency of the electromagnetic field inside the arch and the filter parameters. The most accurate answer to the question of the possibility of placing the AMD in specific conditions can be found by installing it in the place of intended use and conducting the necessary tests.
How to set up a metal detector correctly?
Despite the many settings that affect the performance of METOR metal detectors, the process of setting it up is not complicated. Some manufacturers offer standard settings for certain requirements entered either by password from the metal detector's memory or from a magnetic card. Built-in factory settings are also available in METOR metal detectors, but we suggest using them only as basic ones to create unique user settings suitable for a specific location and tasks.
As an example, let's consider the basic steps of programming the METOR160 metal detector. We will proceed from the condition that the AMD is placed in the best possible way (of all possible for this location) and all necessary electrical parameter settings are made. The programming sequence will be approximately as follows:
1. Select the smallest object that must be detected. At this stage, it is necessary to realize that if damage is caused by an object of a smaller size, then this is a strategic miscalculation of the security service, and not poor performance of the metal detector.
2. Determine a set of safe objects that should not give an alarm signal. Typically, these are 3-4 keys, 6-7 coins of different denominations, a belt buckle, 1-2 pens in a metal case, glasses in a metal frame, a watch with a metal bracelet, a pack of cigarettes.
3. Select the programs that, in your opinion, meet the requirements for detecting the weapon you have selected and the required selectivity. All characteristics of the detection programs are clearly presented in the AMD operating and programming instructions.
4. Enter the factory program settings. The values of the parameters corresponding to them will be automatically entered into the AMD RAM.
5. Set the number of the first program you have selected and select the automatic sensitivity determination mode.
6. Make the required number of passes through the AMD with the test object only, preferably changing its location and orientation. At the end of the test, the metal detector will show the measured sensitivity value.
7. Put the test sample aside and begin passing through the AMD with a set of safe objects. If an alarm occurs, repeat steps 5 through 7 for the next program from the selected ones. If there is no alarm, try increasing the set of safe objects (number of coins, keys, etc.) for each of the selected programs until alarms occur.
8. Set the program for which the set of safe objects was the largest. This will be the main working program. In this case, the sensitivity is set automatically in accordance with the test sample you selected.
9. Set other parameters: speed of passing, volume, tone of the alarm signal, etc. As a result, in less than 30 minutes of work, you will program the arch for the only mode of operation suitable only for you, which no one else can do, not even an employee of the manufacturer, since he may have his own views on the problem of the safety of your facility. With the correct setting of the metal detector, you can be sure that it will react to a dangerous object or a proportionate amount of metal.
The better the metal detector, the less the security service will be distracted by personal inspection in case of safe items being brought in, which will significantly increase the overall security level of any institution. By the way, the US State Department recently tested metal detectors manufactured in the world for use in its institutions, and the only AMD that met the security requirements was METOR200.
If the standard panel design is not suitable for the office interior, is it possible to make an AMD in the form of columns?
Column-shaped metal detectors are manufactured by some companies in Italy and, according to users, their appearance is almost the only quality indicator of such products. They are suitable only for installation in places where there are no strict safety requirements. The selectivity of such metal detectors (the ability of the metal detector to distinguish between dangerous and safe objects) is much lower than that of metal detectors made in the form of panels. In addition, they have worse field homogeneity, lower noise immunity and vibration resistance.
For these reasons, Metorex does not produce AMD in the form of columns. To meet the requirements of interior designers, we produce, upon agreement with the customer, metal detectors with panel coating of any color and texture.
Is it possible to install a metal detector hidden?
METOR metal detectors can be supplied for subsequent hidden installation at the facility. These are the same serial products, but additionally equipped with a set of cables to allow the electronics unit to be moved outside the panels. The width of the passage should not exceed 90 cm, otherwise this will lead to increased field heterogeneity, decreased noise immunity and deterioration of operational characteristics.
When considering the issue of hidden installation of an AMD, it is necessary to take into account the fact that the presence of this metal detector will become known to interested parties within one or two weeks after its installation. The secrecy factor will lose its relevance, and the costs of installing an AMD and the inconvenience in operational work will have an impact for a long time. Open installation of a metal detector, on the contrary, will prevent more attempts at terrorist acts than hidden installation, and will ensure greater order during admission, facilitating the work of the security service. In our opinion, the need for hidden installation of an AMD arises at the second — third line of inspection, in the high sensitivity mode after inspection on openly installed metal detectors, subject to special organizational measures.
Unfortunately, it is not possible to answer all the questions about arched metal detectors within the framework of one article -. Therefore, if you have any questions when choosing this equipment, call the Moscow office of Metorex, where you will receive all the information about the manufactured metal detectors and recommendations for their use. The company's specialists are ready to conduct tests of metal detectors with your participation, seminars and product presentations.
Information about Metorex and the products it manufactures can also be found on the Internet at: http://metorex