The statistics of offenses related to the penetration of intruders into protected premises says that the most “popular” and simplest is breaking the glass of shop windows, windows, as well as breaking locks or doors. The probability of such a scenario, according to experts, is today 66.5%. Only breaking a wall can compete a little with breaking window openings and breaking doors (16.9%), other options (selecting keys, breaking a ceiling, breaking through technological openings) barely exceed 5%.
Who is he, the guard of doors and windows
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 became such means, among which the most prominent position is occupied by a security point magnetic contact detector - a reliable and easy-to-install sensor. Experts give it a high rating in terms of the likelihood of detecting an intrusion attempt onthe 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 be sent to the guard on duty.
With the help of such sensors, it is possible not only to supply an electric signal to turn on the sound alarm, but also to turn on devices that block doors (gates), windows from opening, and objects from moving.
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 contact.
Construction principle and device of the detector
It is in the principle of the construction of the sensor that its high reliability is laid down. It uses the interaction of a sealed magnetically controlled contact (abbreviated as a reed switch), which serves as an executive 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 that exceed 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 andincreased contact resistance. This leads to sudden "sticking" of contacts and failure of the detector.
Since there are no intermediate links in the reed switch of the detector, and the contacts switch a small electric current, the actuating element has almost zero wear. This is also facilitated by the fact that the cylinder contains nitrogen under high pressure, which eliminates the oxidation of contacts.
The control (setting) element can be made in several versions: permanent magnet or magnetic core.
Classification of magnetic contact detectors
Detectors, like any other equipment, are subject to standardization, and this task is 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 risk classes for these sensors: 1 - low risk, 2 - intermediate between 1 and 3 risk classes, 3 - medium risk, 4 - high risk.
The above classification defines the critical and non-critical parameters of the detector for each class. For example, pickup and release distances, protection against alarm loop damage and total loss of supply voltage should be mandatory parameters for all four classes.
low supply voltage.
In the Russian Federation, detectors of class 1 or 2 of the international standard IEC 62642-2-6 are used, that is, they do not require indication of damage to the protected structure, protection against extraneous magnetic influence, low supply voltage.
Requirements for the functionality of magnetic contact detectors
Magnetic contact detectors must meet certain requirements for their functionality, namely:
- the actuation distance excludes an intruder's attempt to penetrate the controlled structure or the movement of the object of protection, as well as the substitution of parts of the detector without giving an alarm signal;
- recovery distance must exclude false triggering of the detector. - the relative displacement of the detector blocks (alignment) should not lead to the termination of its operation;
Indicators of the functionality of magnetic contact detectors depend on the type of sensor, its size, installation location, material of the protected structure.
Sensor markings
Magnitocontact sensor has a standardized name - security point magnetocontact detector IO. This is followed by a digital code characterizing the detection zones and the principle of operation of the detector.
For example, the magnetic contact detector IO 102 (SMK) is marked IO 102, indicating that this equipment belongs to the type of detectors (letter I), is used in security systems (letter O), haspoint detection zone (number 1) and magnetic contact principle of operation (numbers 0 and 2).
Detector selection
The choice of equipment such as an IE magnetic contact security detector is an important step. First of all, it must comply with the place of installation, the material of the protected structure, the conditions of detention, as well as your requirements.
If it is necessary to protect a separate object, then this task will be performed by the security magnetic contact detector IO 102-2 (push-button).
IO 102-20/A2 is perfect for blocking doors, windows and other elements of the room. He is also capable of protecting himself from sabotage ("trap"). That is, the noise immunity of the sensor is an important aspect in matters of its choice. The conditions of the detector should 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 temperatures from minus 40 to plus 50 degrees Celsius.
Attention is also drawn to the characteristics of the reed switch: they must meet your conditions.
Installation of detector units
The magnetic contact point detector and the alarm loop are attached to the surface of the protected structure from the side of the room. The control element is mounted, as a rule, on the moving part of the structure (door, window, lid), and the actuating unit with the alarm loop is mounted on the stationary part (door jamb, frame, body).
The method of mounting the detector depends on the surface on which it is mounted: on wood - with screws, on metal - with screws, on glass - with "Contact" glue. A dielectric gasket must be installed between the detector blocks and the mounting surface.
The described mounting method is open type, but in some cases there is a need for concealed mounting of the sensor. To do this, there are detectors of a cylindrical shape. The very shape of the sensor allows you to install it discreetly 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 maintain the alignment of the ends of the actuator 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, they are 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, the sabotage of the sensors is practically impossible, since the steel will close the action of the external magnet on itself, and it will not reach the final element.
In cases with a non-metallic structure, too, not everything is simple: a certain orientation of the external magnet is required, otherwise its impact on the actuating element may cause the reed switch to open and trigger an alarm.
If these arguments are unconvincing, then there are simpleways to protect against detector tampering:
- use of two sets of magnetic contact sensors with differently directed magnets spaced about 15 mm apart and connected in series;
- using an additional screen in the form of a steel plate with a thickness of 0.5 mm or more;
Faults in brief
Magnetic-contact detector SMK has separate features of the actuating element that limit its use:
- dependence of pressing contacts on the strength of the magnet of the control element and the control current;
- dependence of the switching capacity on the volume of the reed switch cylinder;
- the length of the contacts contributes to their significant bounce during vibration and shock;
Conclusion
Magnetic contact detector 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 low cost. Security systems containing this type of detectors are often preferred. Today, there are many security systems created using innovative technologies, but magnetic contact detectors are still in demand.
