The statistics of offenses related to the penetration of intruders into the guarded premises says that the most “popular” and simplest is breaking glass of windows, windows, as well as breaking locks or doors. The likelihood of developing such a scenario, according to experts, is today 66.5%. Only a wall breach can slightly compete with breaking window openings and breaking doors (16.9%), other options (key selection, ceiling breach, penetration through technological openings) barely exceed 5%.
Who is he, watchman of doors and windows
In order to reliably protect doors, windows, gates, technological openings and other structures from the threat of damage or hacking by intruders, adequate technical security equipment was required. Magnetic-contact detectors have become such means, among which the most prominent position is taken by the magnetic point-contact security detector - a reliable sensor that is easy to install and easy to install. Experts give him a high assessment of the probability of detecting an attempt to enter the territory of the object protected by this device: it is 0.99, that is, in 99% of cases, the offender will be detected by the sensor and the corresponding signal will go to the security guard on-board panel.
With the help of such sensors, it is possible not only to supply an electric signal to turn on the audible alarm, but also to turn on devices that block doors (gates), windows to open, and objects to move.
Protected structures can be made of both magnetic (iron) and non-magnetic material (wood, aluminum, fiberglass, polyvinyl chloride). This does not affect the operation of the magnetic detector.
The principle of construction and device detector
It is in the principle of constructing the sensor that its high reliability is laid. It uses the interaction of a sealed magnetically controlled contact (abbreviated as reed switch), which serves as an actuating element, and a magnet, which serves as a control element.
The actuating element (reed switch) has a very simple design: it immediately combines contact and magnetic systems, which are hermetically sealed in a glass container. This design of the reed switch made it possible to obtain characteristics superior to known contacts: speed, stable parameters, high wear resistance and reliability.
The contacts are made of soft magnetic material, they are separated by a gap of only 300-500 microns, which has certain disadvantages: increased sparking and increased contact resistance. This leads to a sudden "sticking" of the contacts and the failure of the detector.
Since there are no intermediate links in the reed switch of the detector, and the contacts commute a small electric current, the actuator has almost zero wear. This is also facilitated by the fact that the container contains nitrogen under high pressure, which prevents oxidation of the contacts.
The control (master) element can be made in several versions: a permanent magnet or magnetic circuit.
Classification of magnetic detectors
Detectors, like any other equipment, are subject to standardization, and this task has been solved by the international standard IEC 62642-2-6. Its requirements apply to magnetic contact detectors designed to block doors, hatches, windows, containers.
This standard introduces four classes of risk for these sensors: 1 - low risk, 2 - intermediate between classes 1 and 3, 3 - medium risk, 4 - high risk.
The given classification defines the critical and non-critical detector parameters for each class. For example, the response and recovery distances, protection against damage to the alarm loop and the complete loss of supply voltage should be mandatory parameters for all four classes.
In the Russian Federation, detectors of class 1 or 2 of the international standard IEC 62642-2-6 are used, that is, for them the indication of detection of damage to the protected structure, protection against extraneous magnetic influence, low supply voltage is optional.
In the Russian Federation, detectors of class 1 or 2 of the international standard IEC 62642-2-6 are used, that is, for them the indication of detection of damage to the protected structure, protection against extraneous magnetic influence, low supply voltage is optional.
Requirements for the functionality of magnetic detectors
Magnetic contact detectors must meet certain requirements for their functionality, namely:
- the distance of operation eliminates the attempt to penetrate an attacker through a controlled structure or movement of the subject of protection, as well as the substitution of parts of the detector without an alarm;
- the recovery distance should prevent false alarms. - the relative displacement of the detector blocks (alignment) should not lead to the termination of its work;
Indices of functionality of magnetic contact detectors depend on the type of sensor, its size, installation location, material of the protected structure.
Sensor Labeling
The magnetocontact sensor has a standardized name - the detector is a security point magnetocontact IO. The following is a digital code characterizing the detection zone and the principle of the detector.
For example, a magnetic contact detector 102 () is marked 102, which means that this equipment belongs to the type of detectors (letter I), is used in security systems (letter ), has a point detection zone (number 1) and magnetically contact principle actions (numbers 0 and 2).
Detector Selection
The selection of equipment such as a magnetic security contact detector is an important step. First of all, it must correspond to the installation site, the material of the protected structure, the conditions of detention, as well as your requirements.
If it is necessary to protect a stand-alone object, then the detector will perform a magnetocontact security detector 102-2 (push-button).
To block doors, windows and other elements of the room, IO 102-20 / A2 is perfect. He is also able to protect himself from sabotage ("trap"). That is, the noise immunity of the sensor is an important aspect in matters of its choice.
Detector conditions must also be taken into account, and if the environment is explosive, then the IO 102-26 / V sensor is suitable for it.
The sensor is designed for air temperature from minus 40 to plus 50 degrees Celsius.
Attention is also paid to the characteristics of the reed switch: they must meet your conditions.
Mounting detector units
A magnetic point contact detector and an alarm loop are attached to the surface of the guarded structure from the side of the room. The control element is mounted, as a rule, on the moving part of the structure (door, window, cover), and the executive unit with a signal loop - on the stationary one (door jamb, frame, housing).
The detector mounting method depends on the surface on which it is being installed: on wood - with screws, on metal - with screws, on glass - with Contact glue. A dielectric gasket must be installed between the detector units and the mounting surface.
The described mounting method refers to the open type, but in some cases there is a need for hidden mounting of the sensor. For this, there are cylindrical detectors. The very shape of the sensor allows you to install it secretly from prying eyes and not disturb the interior of the room. But this type of installation has a certain drawback: it is fundamentally important to observe the alignment of the ends of the executive and control elements of the detector (within 2-3 mm).
Sensor sabotage and how to deal with it
According to amateurs, magnetic contact detectors are easily bypassed, that is, ignored. And this is done, in their opinion, with the help of an external strong magnet.
In reality, this is far from the case, especially when it comes to steel structures. In this case, sabotage of the sensors is almost impossible, since the steel will close the action of the external magnet, and it will not reach the actuator.
In cases with a nonmetallic construction, not everything is simple either: a certain orientation of the external magnet is required, otherwise its impact on the actuator can cause the reed switch to open and the alarm to trigger.
If these arguments are unconvincing, then there are simple ways to protect against sabotage detectors:
- the use of two sets of magnetocontact sensors with multidirectional magnets located about 15 mm apart and connected in series;
- the use of an additional screen in the form of a steel plate with a thickness of 0.5 mm or more;
Shortly about the shortcomings
The magnetic contact detector SMK has certain features of the actuating element that limit its use:
Conclusion
The magnetic contact detector of the IO is deservedly considered the simplest and most reliable means of protecting objects and structures from intruders. A significant advantage of the sensor is its cheapness. Security systems containing this type of detector are often preferred. Today, there are many security systems created using innovative technologies, but magnetic contact detectors remain in demand until now.