In the field of security, devices designed to detect metal devices have long been used. Today, there are even modifications with a wide range of additional and basic functions. The metal detector frame is one such device. Let's try to figure out what kind of devices they are, we will determine their operating principle and other features.
How does an arched metal detector work?
These devices are stationary (prefabricated or prefabricated) and are highly efficient in detecting metal objects carried through them. By the name you can guess that they are made in the form of an arch. This design is designed so that a person can easily pass through it. The device will immediately detect metal alloys even in slightly conductive substances: plastic, wood, fabrics.
The principle of operation of the metal detector frame is based on the use of radio waves. One wall generates and sends a radio signal to another wall. She receives it and sends it back. If there is any obstacle in the form of a reflecting element (metal) in the path of these waves, the signal does not reach another wall. Also, the signal can bounce off a metal object and return faster than necessary. In any case, when an obstacle is detected for the signal, an audible alarm will sound.
After analyzing the radio waves, the detector can detect the object and show its location on the monitor. Similar modern devices have digital control, programs, microprocessors. Their sensitivity can be set by the operator according to certain parameters. Within the metal detector there are special coils that create a scanning electromagnetic field, the parameters of which can be set.
Kinds
At least there are two types of arched metal detectors: passive and active. The former can detect only products made of ferrous alloys, the latter even detect non-ferrous metals, alloys inside luggage, under clothes, on people's bodies (and inside).
Models can differ in many parameters. In particular, they differ in the following characteristics:
- External design.
- Light indication.
- Sensitivity threshold.
- Quantity function.
- Network work.
As for the functionality, low-sensitivity installations are capable of detecting only large metal objects. They can reveal weapons, explosives with metal striking elements. Models with an increased sensitivity threshold are able to detect small elements. The best are hypersensitive. These detectors detect any metal weighing from one gram. Naturally, the sensitivity largely determines the cost of the detector.
The frames of metal detectors are also divided by the type of radiation that they generate. There are models:
- With a pulse field. The signal is intermittent.
- With a harmonious field. The signal is constant (continuous emission).
The former are more resistant to different vibrations, therefore, they are more reliable. Most of these devices generate an intermittent signal. Detectors with a harmonious field are well protected from interference, but their quality is slightly worse.
Device
This device is a magnetic frame, on the sides and at the top of which there are sensors, coils (windings).Coils serve as sources of electromagnetic signals that form a magnetic field when voltage is applied to them. At the very top of the metal detector frame is a control panel with indicator lights. There are also LEDs in the side walls, however this already depends on the individual design.
The following elements take part in the design:
- Transmitting Coil.
- Receiving coil.
- A control node that can be inside or outside the frame. It is usually mounted on a panel on top, although on some models this panel is not available for ease of installation in airlock cabs.
- Electronic filling in the form of a processor, various microcircuits.
- Autonomous batteries or power supply.
The arch itself is connected to the control units, computer and power. The control panel on the front side also has the following elements:
- The on / off lock key.
- An indicator with LEDs that displays the segments where the item is detected.
- Keyboard input for setting the frame of the metal detector.
- LCD display.
Note that in the design, the most important elements are the transmitting and receiving coils. The efficiency of the device depends on their quality. They generate an electromagnetic uniform field.
Exploitation
There are certain features of the operation of this equipment. If it is too sensitive, then in the settings set the parameters at which there will be no reaction to too small metal objects. Otherwise, the metal detector may squeak in the event of detection of metal zipper on the jacket, rivets on the shirt, dental fillings, hairpins.
However, if you need to find very small items, then the sensitivity of the device is increased. A stationary frame of metal detectors is used at inspection points with visual inspection of detected objects. Personnel who work near the installation are advised to wear clothes without metal elements.
Initially, the detectors have factory settings and programs for detecting weapons, as well as items of standard threats. If necessary, they can be programmed to detect items of non-standard sizes.
Installation Rules
Installation of metal detector frames begins with the assembly of the device according to the instructions. The panels are arranged according to the scheme, each should stand in its place relative to the central unit. The central unit is installed in the connectors. The whole structure is fastened with bolts, which are necessarily included. The power cord usually connects to one of the side panels. It also includes a power cord. For ease of installation, some models in both panels have a connector for connecting the power cord.
In some cases, if the detector is installed close to metal elements (for example, to a reinforced concrete wall, where there is reinforcement), then certain sensitivity parameters are set in the settings, because the metal nearby can cause interference. Then, using the key, the device turns on, self-diagnosis is activated, after which it is ready for operation.
Precautionary measures
A stationary or portable metal detector frame is a highly sensitive equipment, and certain rules must be followed when using it. Firstly, the space within a radius of 3-4 meters from its installation is cleaned of metal, all power cables of electrical networks are removed, the installation of radio devices is not allowed nearby, etc. Electric motors, transformers and electrical panels can also not be nearby. Lifts, turnstiles or gates nearby can cause interference.
Secondly, nearby arched metal detectors are necessarily separated by distance and adjusted so that they do not interfere with each other.The mounting location also affects the sensitivity, and if it is high, the number of false positives can be very high. With low sensitivity and incorrect setup and installation, malfunctions are possible.
Harm to humans
Note that the harmfulness of the metal detector frame is practically absent. Electromagnetic fields are safe for a person, even if he has an electrical stimulator on his heart. They are harmless to pregnant women, children, do not damage digital media, cards with magnetic stripes. However, at many airports, airport employees often ask people if they have an electrical stimulator on their heart, and if so, they inspect it manually, without passing through a detector. It is possible that in many places old facilities are used that are harmful to humans.
Application advantages
With just one such installation, you can organize a passage for people to various events, events. A single detector can provide a throughput of 10 to 100 people per minute. High-quality devices generate a continuous and uniform electromagnetic field, which accurately determines the presence of metal elements carried through the device. Poor detectors can be equipped with blind spots in which small objects are not detected. However, most modern models guarantee the probability of metal detection with a probability of 100%. More advanced appliances can even recognize an item.
Also, the advantages include the possibility of operating such equipment on the streets in the presence of a waterproof housing according to the IP55 standard. For rooms there are models with IP22 protection.
Minuses
As for the shortcomings, it is first of all worth highlighting the bulkiness and the need for installation. Even relatively compact and mobile arch metal detectors must be delivered to their destination, made installations, find a power source to connect. If the installation is carried out on the street, the task is complicated. In addition to installation, it is also necessary to carry out the adjustment, moreover, correctly. If the parameters are set incorrectly, then a large number of false positives or failures are possible, which is even worse.
Conclusion
Now you understand how the metal detector frame works. This equipment is used today at almost all infrastructure facilities: airports, train stations, etc. It is also used at various enterprises and factories. When organizing festive events or concerts, security services also install these systems to ensure a high level of security for holding a concert or a holiday.
Such detectors are constantly being improved, new methods for identifying dangerous carried objects and weapons are emerging, new algorithms are being developed, although the principle of scanning does not change.
