home > A little about everything > Detector optoelectronic passive volumetric. The best infrared thermometers according to customer reviews. Other protection elements of IR detectors

Detector optoelectronic passive volumetric. The best infrared thermometers according to customer reviews. Other protection elements of IR detectors

Currently, passive optical-electronic infrared (IR) detectors occupy a leading position in the choice of protection of premises from unauthorized intrusion at security facilities. Aesthetic appearance, ease of installation, configuration and maintenance often give them priority over other detection tools.

Passive optical-electronic infrared (IR) detectors (they are often called motion sensors) detect the fact of a person entering the protected (controlled) part of the space, generate an alarm signal and, by opening the contacts of the executive relay (RCP relay), transmit an “alarm” signal to the warning means . As a means of warning, terminal devices (UO) of notification transmission systems (SPI) or a fire and security alarm control device (PPKOP) can be used. In turn, the above devices (UO or PPKOP) broadcast the received alarm notification via various data transmission channels to the central monitoring station (CMS) or the local security console.

The principle of operation of passive optical-electronic IR detectors is based on the perception of level changes infrared radiation temperature background, the sources of which are the body of a person or small animals, as well as all kinds of objects that are in their field of vision.

Infrared radiation is heat that is emitted by all heated bodies. In passive optical-electronic IR detectors, infrared radiation enters the Fresnel lens, after which it is focused on a sensitive pyroelement located on the optical axis of the lens (Fig. 1).

PIR detectors receive streams infrared energy from objects and are converted by the pyro receiver into an electrical signal, which is fed through the amplifier and the signal processing circuit to the input of the alarm generator (Fig. 1)1.

In order for the intruder to be detected by the IR passive sensor, the following conditions must be met:

Passive IR sensors consist of three main elements:

Depending on the version of the Fresnel lens, passive optoelectronic IR detectors have different geometric dimensions controlled space and can be both with a three-dimensional detection zone, and with a surface or linear one. The range of action of such detectors lies in the range from 5 to 20 m. The appearance of these detectors is shown in fig. 2.

Optical system

Modern IR sensors are characterized by a wide variety of possible beam patterns. The sensitivity zone of IR sensors is a set of rays of various configurations, diverging from the sensor in radial directions in one or more planes. Due to the fact that IR detectors use dual pyro receivers, each beam in the horizontal plane is split into two:

The detector sensitivity zone can look like:

The diversity and complex configuration of the forms of the sensitivity zone are primarily due to the following factors:

small rooms

It is expedient to dwell on the requirement of uniform sensitivity in more detail. The signal at the output of the pyro receiver, all other things being equal, is the greater, the greater the degree of overlapping by the violator of the detector sensitivity zone and the smaller the beam width and the distance to the detector. To detect an intruder at a large (10...20 m) distance, it is desirable that the beam width in the vertical plane does not exceed 5°...10°, in which case the person almost completely blocks the beam, which ensures maximum sensitivity. At shorter distances, the sensitivity of the detector in this beam increases significantly, which can lead to false alarms, for example, from small animals. To reduce uneven sensitivity, optical systems are used that form several inclined beams, while the IR detector is installed at a height higher than human height. The total length of the sensitivity zone is thus divided into several zones, and the beams “nearest” to the detector are usually made wider to reduce sensitivity. This ensures almost constant sensitivity over the distance, which, on the one hand, helps to reduce false positives, and, on the other hand, increases the detectability by eliminating dead zones near the detector.

When building optical systems of IR sensors, the following can be used:

Typically, each segment of a Fresnel lens forms its own beam pattern. The use of modern lens manufacturing technologies makes it possible to ensure almost constant detector sensitivity for all beams by selecting and optimizing the parameters of each lens-segment: segment area, tilt angle and distance to the pyroelectric receiver, transparency, reflectivity, degree of defocusing. Recently, the technology of manufacturing Fresnel lenses with complex precise geometry has been mastered, which gives a 30% increase in the collected energy compared to standard lenses and, accordingly, an increase in the level of a useful signal from a person at long distances. The material from which modern lenses are made protects the pyroelectric receiver from white light. The unsatisfactory operation of the IR sensor can be caused by such effects as heat fluxes resulting from heating of the electrical components of the sensor, the ingress of insects on sensitive pyro-receivers, and possible re-reflections of infrared radiation from the internal parts of the detector. To eliminate these effects in the latest generation of IR sensors, a special hermetic chamber is used between the lens and the pyro receiver (sealed optics), for example, in new IR sensors from PYRONIX and C&K. According to experts, modern high-tech Fresnel lenses are almost as good as mirror optics in terms of their optical characteristics.

Mirror optics as the only element of an optical system is rarely used. IR sensors with mirror optics are available, for example, from SENTROL and ARITECH. The advantages of mirror optics are the possibility of more accurate focusing and, as a result, an increase in sensitivity, which makes it possible to detect an intruder at long distances. The use of several specially shaped mirrors, including multi-segment ones, makes it possible to provide an almost constant distance sensitivity, and this sensitivity at long distances is approximately 60% higher than for simple Fresnel lenses. With the help of mirror optics, it is easier to protect the near zone located directly under the sensor installation site (the so-called anti-tamper zone). By analogy with interchangeable Fresnel lenses, IR sensors with mirror optics are equipped with replaceable detachable mirror masks, the use of which allows you to select the desired shape of the sensitivity zone and makes it possible to adapt the sensor to various configurations of the protected premises.

Modern high quality IR detectors use a combination of Fresnel lenses and mirror optics. In this case, Fresnel lenses are used to form a sensitivity zone at medium distances, and mirror optics are used to form an anti-sabotage zone under the sensor and to provide a very large detection distance.

Pyro receiver:

The optical system focuses IR radiation on a pyro-detector, which is used in IR sensors as an ultra-sensitive semiconductor pyroelectric converter capable of registering a difference of several tenths of a degree between the temperature of the human body and the background. The change in temperature is converted into an electrical signal, which, after appropriate processing, triggers an alarm. In IR sensors, dual (differential, DUAL) pyroelements are usually used. This is due to the fact that a single pyroelement reacts in the same way to any change in temperature, regardless of whether it is caused by the human body or, for example, heating a room, which leads to an increase in the frequency of false positives. In the differential circuit, the signal of one pyroelectric element is subtracted from another, which makes it possible to significantly suppress interference associated with changes in the background temperature, as well as significantly reduce the effect of light and electromagnetic interference. The signal from a moving person appears at the output of the dual pyroelectric element only when the person crosses the beam of the sensitivity zone and is an almost symmetrical bipolar signal, close in shape to the period of a sinusoid. For this reason, the beam itself for a dual pyroelement splits into two in a horizontal plane. In the latest models of IR sensors, in order to further reduce the frequency of false positives, quadruple pyroelements (QUAD or DOUBLE DUAL) are used - these are two dual pyro receivers located in one sensor (usually placed one above the other). The observation radii of these pyro receivers are made different, and therefore the local thermal source of false alarms will not be observed in both pyro receivers simultaneously. At the same time, the geometry of the location of the pyroelectric receivers and the scheme of their inclusion are chosen in such a way that the signals from a person are of opposite polarity, and electromagnetic interference causes signals in two channels of the same polarity, which leads to the suppression of this type of interference. For quad pyroelectric elements, each beam is split into four (see Fig. 2), and therefore the maximum detection distance when using the same optics is approximately halved, since for reliable detection, a person must block both beams from two pyro receivers with his height. To increase the detection distance for quad pyroelements allows the use of precision optics that form a narrower beam. Another way to correct this situation to some extent is the use of pyroelements with complex interlaced geometry, which is used by PARADOX in its sensors.

Signal processing unit

The signal processing unit of the pyro receiver must ensure reliable recognition of a useful signal from a moving person against the background of interference. For IR sensors, the main types and sources of interference that can cause false alarms are:

The selection by the processing unit of the useful signal against the background of interference is based on the analysis of the signal parameters at the output of the pyro receiver. These parameters are the magnitude of the signal, its shape and duration. The signal from a person crossing the beam of the IR sensor sensitivity zone is an almost symmetrical bipolar signal, the duration of which depends on the speed of the intruder, the distance to the sensor, the width of the beam, and can be approximately 0.02 ... ,1…7 m/s. Interference signals are mostly asymmetric or have a duration different from useful signals (see Fig. 3). The signals shown in the figure are very approximate, in reality everything is much more complicated.

The main parameter analyzed by all sensors is the magnitude of the signal. In the simplest sensors, this recorded parameter is the only one, and its analysis is performed by comparing the signal with a certain threshold, which determines the sensitivity of the sensor and affects the frequency of false alarms. In order to increase resistance to false alarms in simple sensors the pulse counting method is used when it counts how many times the signal exceeded the threshold (that is, in fact, how many times the intruder crossed the beam or how many beams it crossed). In this case, the alarm is generated not when the threshold is exceeded for the first time, but only if, within a certain time, the number of exceedances becomes greater than the specified value (usually 2…4). The disadvantage of the pulse counting method is the degradation of sensitivity, which is especially noticeable for sensors with a sensitivity zone such as a single curtain and the like, when the intruder can only cross one beam. On the other hand, when counting pulses, false alarms are possible due to repeated interference (eg electromagnetic or vibration).

In more complex sensors, the processing unit analyzes the bipolarity and symmetry of the waveform from the output of the differential pyro receiver. The specific implementation of such processing and the terminology used to refer to it1 may vary from manufacturer to manufacturer. The essence of processing is to compare a signal with two thresholds (positive and negative) and, in some cases, to compare the magnitude and duration of signals of different polarity. It is also possible to combine this method with separate counting of excesses of positive and negative thresholds.

Signal duration analysis can be carried out both by a direct method of measuring the time during which the signal exceeds a certain threshold, and in the frequency domain by filtering the signal from the output of the pyrodetector, including using a “floating” threshold that depends on the frequency analysis range.

Another type of processing designed to improve the performance of IR sensors is automatic thermal compensation. Temperature range environment At 25°С…35°С, the sensitivity of the pyrodetector decreases due to a decrease in the thermal contrast between the human body and the background; with a further increase in temperature, the sensitivity increases again, but “with the opposite sign”. In the so-called “conventional” temperature compensation schemes, the temperature is measured, and when it rises, the gain is automatically increased. With “real” or “two-sided” compensation, an increase in thermal contrast is taken into account for temperatures above 25°С…35°С. The use of automatic thermal compensation ensures that the sensitivity of the IR sensor is almost constant over a wide temperature range.

The listed types of processing can be carried out by analog, digital or combined means. In modern IR sensors, digital processing methods are increasingly being used using specialized microcontrollers with ADCs and signal processors, which allows for detailed processing of the fine structure of the signal to better distinguish it from noise. Recently, there have been reports of the development of fully digital IR sensors that do not use analog elements at all.
As is known, due to the random nature of useful and interfering signals, processing algorithms based on the theory of statistical decisions are the best.

Other protection elements of IR detectors

IR sensors intended for professional use use so-called anti-masking circuits. The essence of the problem lies in the fact that conventional IR sensors can be disabled by an intruder by preliminary (when the system is not armed) gluing or painting over the input window of the sensor. To combat this way of bypassing IR sensors, anti-masking schemes are used. The method is based on the use of a special IR channel that is triggered when a mask or reflective barrier appears at a small distance from the sensor (from 3 to 30 cm). The anti-masking circuit operates continuously while the system is disarmed. When the fact of masking is detected by a special detector, a signal about this is sent from the sensor to the control panel, which, however, does not issue an alarm signal until it is time to arm the system. It is at this moment that the operator will be given information about the masking. Moreover, if this masking was accidental (a large insect, the appearance of a large object for some time near the sensor, etc.) and by the time the alarm was set it had eliminated itself, the alarm is not generated.

Another protective element that almost all modern IR detectors are equipped with is a tamper-evident contact sensor, which signals an attempt to open or tamper with the sensor housing. Tamper and masking sensor relays are connected to a separate security loop.

To eliminate IR sensor triggers from small animals, either special lenses with a dead zone (Pet Alley) from floor level to a height of about 1 m are used, or special methods signal processing. It should be taken into account that special processing signals allows animals to be ignored only if they are total weight does not exceed 7 ... 15 kg, and they can approach the sensor no closer than 2 m. So if there is a jumping cat in the protected area, then such protection will not help.

For protection against electromagnetic and radio interference, tight surface mounting and metal shielding are used.

Installation of detectors

Passive optical-electronic IR detectors have one remarkable advantage over other types of detection devices. It is easy to install, set up and maintain. Detectors of this type can be installed both on a flat surface of a load-bearing wall and in the corner of a room. There are detectors that are placed on the ceiling.

A competent choice and tactically correct use of such detectors are the key to reliable operation devices, and the entire security system as a whole!

When choosing the types and number of sensors to ensure the protection of a particular object, one should take into account the possible ways and means of penetration of the intruder, the required level of detection reliability; expenses for the acquisition, installation and operation of sensors; features of the object; performance characteristics of sensors. A feature of IR-passive sensors is their versatility - with their use it is possible to block from the approach and penetration of a wide variety of premises, structures and objects: windows, shop windows, counters, doors, walls, ceilings, partitions, safes and individual objects, corridors, room volumes. At the same time, in some cases, a large number of sensors will not be required to protect each structure - it may be sufficient to use one or more sensors with the desired configuration of the sensitivity zone. Let us dwell on the consideration of some features of the use of IR sensors.

The general principle of using IR sensors is that the rays of the sensitivity zone should be perpendicular to the intended direction of movement of the intruder. The location of the sensor should be chosen in such a way as to minimize the dead zones caused by the presence of large objects in the protected area that block the beams (for example, furniture, indoor plants). If the doors open inward in the room, the possibility of masking the intruder with open doors should be taken into account. If dead zones cannot be eliminated, multiple sensors should be used. When blocking individual objects, the sensor or sensors must be installed so that the rays of the sensitivity zone block all possible approaches to the protected objects.

The range of permissible suspension heights specified in the documentation (minimum and maximum heights) must be observed. This applies in particular to directional patterns with inclined beams: if the height of the suspension exceeds the maximum allowable, then this will lead to a decrease in the signal from the far zone and an increase in the dead zone in front of the sensor, but if the suspension height is less than the minimum allowable, this will lead to a decrease in the range detection while reducing the dead zone under the sensor.

1. Detectors with a volume detection zone (Fig. 3, a, b), as a rule, are installed in the corner of the room at a height of 2.2-2.5 m. In this case, they evenly cover the volume of the protected room.

2. Placement of detectors on the ceiling is preferable in rooms with high ceilings from 2.4 to 3.6 m. These detectors have a denser detection zone (Fig. 3, c), and existing pieces of furniture affect their operation to a lesser extent.

3. Detectors with a surface detection zone (Fig. 4) are used to protect the perimeter, for example, non-solid walls, door or window openings, and can also be used to limit the approach to some values. The detection zone of such devices should be directed, as an option, along the wall with openings. Some detectors can be installed directly above the opening.

4. Detectors with a linear detection zone (Fig. 5) are used to protect long and narrow corridors.

Interference and false positives

When using passive optical-electronic IR detectors, it is necessary to keep in mind the possibility of false alarms that occur due to various types of interference.

Interference of thermal, light, electromagnetic, vibration nature can lead to false alarms of IR sensors. Despite the fact that modern IR sensors have a high degree of protection against these effects, it is still advisable to adhere to the following recommendations:

bright light

Thermal interference - due to the heating of the temperature background when exposed to solar radiation, convective air flows from the operation of radiators of heating systems, air conditioners, drafts.
Electromagnetic interference - caused by pickups from sources of electrical and radio emissions on individual elements of the electronic part of the detector.
Extraneous interference - associated with the movement of small animals (dogs, cats, birds) in the detection zone of the detector. Let us consider in more detail all the factors affecting the normal performance of passive optical-electronic IR detectors.

Thermal noise

This is the most dangerous factor, which is characterized by a change in the temperature background of the environment. The impact of solar radiation causes a local increase in the temperature of individual sections of the walls of the room.

Convective interference is caused by the influence of moving air flows, for example, from drafts with an open window, cracks in window openings, as well as during the operation of household heating appliances - radiators and air conditioners.

Electromagnetic interference

They occur when any sources of electrical and radio emission are turned on, such as measuring and household equipment, lighting, electric motors, radio transmitting devices. Strong interference can also be created from lightning discharges.

Extraneous interference

Small insects, such as cockroaches, flies, wasps, can be a peculiar source of interference in passive optical-electronic IR detectors. If they move directly along the Fresnel lens, a false alarm of this type of detector may occur. The danger is also represented by the so-called domestic ants, which can get inside the detector and crawl directly over the pyroelement.

Mounting errors

Special place in the wrong or wrong work passive optical-electronic IR detectors are occupied by installation errors when performing installation work for these types of devices. Let's pay attention to vivid examples of incorrect placement of IR detectors in order to avoid this in practice.

On fig. 6 a; 7 a and 8 a shows the correct, correct installation of the detectors. You just need to install them this way and nothing else!

In figures 6 b, c; 7 b, c and 8 b, c show options for incorrect installation of passive optoelectronic IR detectors. With this setting, it is possible to miss real intrusions into protected premises without issuing an “Alarm” signal.

Do not install passive optical-electronic detectors in such a way that they are exposed to direct or reflected rays of sunlight, as well as the headlights of passing vehicles.
Do not point the detection zone of the detector at the heating elements of the heating and air conditioning systems of the room, at the curtains and curtains, which can fluctuate from drafts.
Do not place passive optical-electronic detectors near sources of electromagnetic radiation.
Seal all openings of the passive optical-electronic IR detector with sealant from the product kit.
Destroy insects that are present in the protected area.

Currently, there is a huge variety of detection tools that differ in the principle of operation, scope, design and performance.

The right choice of a passive optical-electronic IR detector and its installation location is the key to reliable operation of the system burglar alarm.

When writing the article, materials from the journal “Security Systems” No. 4, 2013 were also used

In security systems, the volumetric optical-electronic security detector is an integral element.

It is also used in technology smart House”, where, upon detection of warm-blooded objects, lighting is temporarily turned on in the room or in the adjacent territory.

It gained popularity due to its simplicity of design and low cost. The operation of the sensor is based on the sensor's response to infrared radiation.

Since man is a warm-blooded creature, he reacts to his presence.

Types of detectors

Optoelectronic security detector is presented on the market big amount devices that differ in characteristics and purpose.

According to the way they work with radiation, they are divided into active and passive.

The former themselves emit IR radiation and determine the presence or absence of a person in the protection zone by the received reflected energy. The second work only on reception.

According to the configuration of the controlled area, they are divided into volumetric, surface and linear. The optical-electronic surface security detector responds to changes in radiation only in one plane.

They are used to control openings, doors, windows. Linear are used in the protection of perimeters. The volumetric optoelectronic detector is used when it is necessary to control any sector of space, usually indoors.

Advantages of optoelectronic detectors

The advantages of IR detectors include:

accurate determination of the range and angle of the controlled area;
the ability to work outdoors;
absolute safety for human health.

The disadvantages of IR detectors are:

false alarms that occur when bright light hits the lens due to warm air currents;
work in a narrow temperature range.

A conventional pulse-counting sensor can be fooled when moving slowly.

These shortcomings are deprived of an optical-electronic detector on a microprocessor. He is able to compare the radiation from a real object with the patterns embedded in the memory, due to this, the number of false positives is sharply reduced.

Principle of operation

The main element of an optical-electronic detector is a pyroelectric converter, which converts infrared radiation into an electric current.

A faceted Fresnel lens is used to hit the pyro receiver.

With the help of many small prisms, IR radiation from each sector of the controlled space enters the photodetector.

The signal level at the output of the device is constantly monitored for exceeding the threshold value. When this happens, it means that an object with a temperature above the background has appeared in the protection zone.

The sensor sends an alarm signal to the control panel. To reduce the amount of false noise, 2-4 sensors and digital signal processing are used.

Detector design

The detector is a small box with a lens on the front surface. The lens is molded from plastic in the form of many small lenses.

Each of them has a certain shape and orientation in space, depending on which sensor is volumetric, surface or linear.

In any case, all lenses direct the collected radiation to the pyro receiver. He is on printed circuit board mounted on the back of the case.

When the case is opened, a tamper is activated, which sends a signal to the control panel. An anti-masking circuit is used to protect the sensor during the "disarmed" mode. She reports about the gluing of the lens with adhesive tape or other material.

In lighting control devices, there is a powerful relay controlled by a sensor in the housing. In addition, there is a photocell that allows the inclusion of light lamps only in low light.

Features of use

When using IR sensors, it must be taken into account that they must be located in areas where there are no heat fluxes or bright light sources.

Devices must be mounted on solid surfaces, without strong vibration. In permanent structures, the sensor is installed on a wall or ceiling. In rooms made of lungs metal structures they are mounted on the bearing elements of the building.

When used as a lighting control device, it is necessary to coordinate the power of light lamps with the capabilities of a relay or an electronic key. The mounting point is chosen in such a way that there are no obstacles in the control zone.

To increase the reliability of intruder detection, it is recommended to use it in tandem with a microwave sensor. When monitoring window openings, it is necessary to use it together with an acoustic detector.

IR sensors can be used together with video cameras, cameras, light and sound annunciators, turning them on when the control zone is violated by a warm-blooded object.

TOP 5 models

Pyronix

Pironix on Russian market has been operating for a very long time and has established itself as an excellent manufacturer of inexpensive and reliable IR sensors for security systems.

It provides protection against animals up to 20 kg. It has increased noise immunity from electromagnetic interference, background radiation fluctuations and convective heat flows.

Protection against opening is provided. Has the ability to work in address security systems.

Range 10 m. Captures objects moving at a speed of 0.3-3 m/s. Operates in the range -30+50 ⁰С. Service life 10 years.

Optex

Operating frequency 868.1 MHz. The sector of control is 110⁰ with a radius of 12 m.

Designed for indoor use. Additional lenses are provided that provide the “corridor”, “curtain” mode and protection from animals.

Video: Surveillance volumetric optical-electronic street detector "Piron-8"

People go to great lengths to protect their property. Provided special equipment, which allows you to quickly detect an outsider on the territory and take the necessary measures. You should not spare money for the installation of high-tech devices - the products fully justify their cost. You can purchase a linear optoelectronic detector, which has already proven itself on the positive side.

Device features

Such products can be installed both in residential premises and in large industrial facilities. The detection zone depends on the power of the optical system. Typically, a linear optoelectronic detector signals when an object has already entered the territory. Many consider this a minus, but this is just the principle of operation of this device.

For the device to function properly, it must be installed correctly. The instructions indicate where and how exactly the linear optoelectronic detector should be mounted. There are a few simple tips to remember:

do not install the device near heating devices;
protect the product from direct sunlight;
do not place objects within the range of the device that will create “dead” zones;
do not point the fan at the sensor.

Most of the restrictions are related to temperature changes, since a linear optoelectronic detector can generate and give a false signal. In addition, negative external factors can affect the quality of the device. It is likely that it will fail much earlier than with proper operation.

Advantages of the device

Such a product as a linear optoelectronic detector enjoys well-deserved popularity among customers. There are objective reasons for this. The main advantages of the device:

prompt response;
ease of installation;
low price.

Buyers note that the cost of equipment is quite affordable. And the scope of use of such detectors is quite wide. They are suitable for apartments, industrial sites, warehouses, shopping malls and so on.

Before buying a device, it is better to consult with specialists. They will advise which model to prefer and why. Professionals will also talk about the features of installation.

The last question remains - where to buy the product? Our company "Sintez Security" is engaged in the implementation and installation of security equipment various types. If you contact us, the masters will quickly arrive at the specified address, do everything carefully and competently.

Why buy products from us

The well-known company Synthesis Security has been operating in this market segment for many years. Our clients include both companies and individuals. We try to make everyone happy with the service. We are sure we can do it.

Synthesis Security guarantees excellent product quality and low prices. Our products are much cheaper than many of our competitors. Therefore, you can save not only money, but also nerves. Contact us today!

You can buy IR linear optoelectronic devices from us at a low price - there are 15 pcs in the catalog, compare, study the characteristics.

Lecture 6

Active optical-electronic detectors

Active optical-electronic detectors are used to protect internal and external perimeters, windows, shop windows, individual items. They generate an alarm when the reflected flow changes (single-position detectors) or the received flow (two-position detectors) ceases (changes) of optical radiation energy caused by the movement of the intruder in the detection zone. The principle of operation of the detectors is based on the directed distribution, reception and analysis of the received infrared radiation.

The detection zone of the detector has the form of an invisible beam barrier between the emitter and the receiver, formed by one or more parallel narrow beams located in a vertical plane; it differs from detector to detector, as a rule, by the range and the number of beams.

Install the emitter and receiver on strong, non-deformable structures;

Do not expose the receiver to sunlight and car headlights, as well as direct sunlight on the lenses, as this can lead to overheating and premature failure of photodiodes and LEDs.

The influence of these factors can be eliminated by using opaque screens; prevent foreign objects from being closer than 0.5 m from the space through which the beam passes.

Typical representatives of this class of products are the detectors of domestic production "Vector" and "SPEK".

Passive optical-electronic detectors

Passive optoelectronic infrared detectors received the most wide use. This is due to the fact that with the help of optical systems specially designed for them, it is possible to quickly and easily obtain detection zones of various shapes and sizes and use them to protect objects of almost any configuration: residential, industrial, commercial and administrative premises; building structures: shop windows, windows, doors, walls, ceilings; open areas, internal and external perimeters; individual items: museum exhibits, computers, office equipment, etc.

The principle of operation of the detectors is based on registering the difference between the intensity of infrared radiation coming from an intruder penetrating into the controlled area and the background temperature at the protected object. All bodies with a temperature above absolute zero are sources of infrared radiation. This also applies to a person whose various parts of the body have a temperature of 25 ... 36 ° C. Obviously, the intensity of IR radiation from a person will depend on many factors, such as his clothes. Nevertheless, if a person appears on an object that does not have sources of IR radiation with a changing temperature, the total IR radiation flux from the controlled area also changes. These changes are recorded by a passive optical-electronic infrared detector.

The sensitive element of the detector is a pyroelectric transducer, on which infrared rays are focused using a mirror or lens optical system (the latter are currently the most widely used). Modern detectors use a double pyroelectric transducer (pyroelectric element). Two pyroelements are connected in anti-parallel and connected to a source follower mounted in the same housing. Thus, this is not just a pyroelement, but a pyro receiver that converts the input signal - thermal IR radiation into an electrical signal and pre-processes it. The counter-parallel connection of pyroelements makes it possible to implement the following algorithm for their operation. If the IR radiation incident on both pyroelements is the same, then the current generated by them is equal in magnitude and opposite in direction. Therefore, the input signal at the input of the amplifier will be zero. With asymmetric illumination of the pyroelements, their signals will differ and a current will appear at the input of the amplifier. The signals from the pyro receiver are processed by a logic block that controls the output element of the detector circuit, which issues an alarm notification to the alarm loop of the control panel.

The use of a pyro receiver with two sensitive areas can significantly reduce the likelihood of false alarms under the influence of external factors, such as convective air flows, light interference, etc.

The detection zone of the detector is a spatial discrete system consisting of elementary sensitive zones in the form of beams located in one or more tiers or in the form of thin wide plates located in a vertical plane. Since the detector's pyro-receiver has two sensitive areas, each elementary sensitive zone of the detector also consists of two beams. A typical volumetric detector detection zone is shown in fig. 7.1.

The detection zone of the detector is formed using a special optical system. The most widely used optical systems with a Fresnel lens. This is a structure made of a special material (polyethylene) that has the required optical properties. The lens consists of separate segments, each of which forms a corresponding beam of the detector's detection zone. Standard detection zones

can be corrected by gluing individual segments of the Fresnel lens. In this case, individual beams are excluded from the detection zone.

Conventionally, detector detection zones can be divided into three main types:

Surface type "fan", "curtain", "curtain" or "beam barrier";

Linear type "corridor";

Volumetric, including the “cone” type for ceiling detectors.

Typical detection zones of passive optical-electronic infrared detectors are shown in fig. 7.2.

To ensure stable operation of the detector, it is recommended to adhere to the following rules:

Do not install the detector above heating devices;

Do not point the detector at air conditioners, radiators, warm air fans, spotlights, incandescent lamps and other sources that cause rapid temperature changes;

Do not expose the detector to direct sunlight;

Do not allow animals and objects (curtains, partitions, cabinets, etc.) that can create “dead” zones to be in the detection zone.

Modern passive optical-electronic infrared detectors use digital signal processing, carry out constant self-monitoring, have increased resistance to various destabilizing factors and an optimal price-quality ratio. All this makes them the most common class of burglar alarms. The variety of their types, produced by the world's leading companies engaged in the production of security equipment, creates constant competition in the consumer market. Basically, detectors from different companies have approximately the same performance characteristics in their classes.

Typical representatives of this class of products are domestically produced detectors of the "Photon", "Icarus", "Astra" series.

Radio wave detectors

Radio wave detectors can be used to protect the volume of enclosed spaces, internal and external perimeters, individual items and building structures, open areas. They generate an intrusion notification when the field of electromagnetic waves of ultrahigh frequency (SHF) is disturbed, caused by the movement of the intruder in the detection zone. Radio wave detectors are single-position and two-position. In single-position detectors, the receiver and transmitter are combined in one housing, while in two-position detectors they are structurally made in the form of two separate blocks.

The detection zone of the detector (as with ultrasonic detectors) has the shape of an ellipsoid of rotation or a teardrop shape and differs from detector to detector, as a rule, only in size. A typical detection zone of a single position detector is shown in fig. 7.3.

The principle of operation of single-position radio wave detectors, as well as for ultrasonic ones, is based on the Doppler effect, which consists in changing the frequency of the signal reflected from a moving object. Single-position radio wave detectors are used to protect the volume of premises, open areas, and individual objects. The principle of operation of two-position detectors is based on the creation in the space between the transmitter and receiver electromagnetic field, which forms the detection zone in the form of an elongated ellipsoid of rotation and registers changes in this field when the intruder crosses the detection zone. They are used to protect the perimeter.

In radio wave detectors, as already noted, electromagnetic waves of ultrahigh frequency are used. Length

wave is usually about 3 cm (10.5 ... 10.7 GHz). The main advantage of centimeter waves, in comparison with light and acoustic waves, is their almost complete insensitivity to changes and inhomogeneity of the air environment.

Microwave radio waves propagate in a straight line. Objects whose permittivity differs from air are an obstacle for centimeter waves, but most often they are translucent. Objects having solid metal surfaces are opaque reflective obstacles.

To ensure the stable operation of radio wave detectors, it is recommended to adhere to the following rules:

Do not install detectors on conductive structures (metal beams, wet brickwork etc.), since a double ground loop appears between the detector and the power source, which can cause a false alarm of the detector;

Move out of the detection zone oscillating or moving objects with a significant reflective surface, as well as large-sized objects that can create "dead" zones, or form the detection zone in such a way that these objects do not fall into it.

In the presence of "dead" zones, it is necessary to ensure that they do not form a continuous path to material values for the intruder; for the period of protection, lock doors, windows, vents, transoms, hatches, and also turn off ventilation and power switching installations; prevent plastic pipes and window panes from entering the detection zone, through which water can move.

Effective methods reducing the influence of these factors are the following:

Fixing objects that can move;

Selection of the appropriate direction of radiation of the detector, as well as the use of radio-tight screens, for example, in the form of metal meshes in front of objects whose vibrations or movement cannot be eliminated;

Elimination of the possibility of triggering the detector when small animals and insects appear in the detection zone by choosing the height of the detector suspension and orienting its radiation direction parallel to the floor;

Selection of an appropriate delay of the detector response time and treatment of the detector installation site with special chemicals;

Disabling fluorescent lighting sources for the period of protection.

If this is not possible, care must be taken to ensure that there are no vibrations of the fittings of the luminaires, flashing or other transient processes in the lamps themselves, which usually occur before the failure of the lamp; do not orient the detector to window openings, thin walls and partitions, behind which movement of large-sized objects is possible during the protection period; do not use detectors at objects near which powerful radio transmitting means are located.

Typical representatives of this class of products are domestically produced detectors of the Argus, Volna, Fon, Radiy, Linar series.

Optoelectronic detectors.

Optoelectronic There are two fundamentally different types of detectors: passive and active. In this lecture, we will consider only detectors used for burglar alarm purposes. The fire component will be discussed in a lecture on fire detectors. Let me remind you that passive detectors do not emit anything into the environment, but only analyze the incoming information. Active for the purpose of detecting penetrations, they radiate something into the environment and, based on the response, draw the appropriate conclusions. Active detectors can be either monoblock (emitter and receiver in one housing), or two or more block ones, when the emitter and receiver are separated.

Consider first

Passive optoelectronic detectors

Currently passive optoelectronic infrared ( IR) detectors occupy a leading position in the choice of protection of premises from unauthorized intrusion at the objects of protection. Aesthetic appearance, ease of installation, configuration and maintenance make them a priority compared to other detection tools.

The principle of operation of passive optical-electronic IR detectors is based on the perception of a change in the level of infrared radiation of the temperature background, the sources of which are the body of a person or small animals, as well as all kinds of objects in their field of vision.

Infrared radiation is heat that is emitted by all heated bodies. In passive optical-electronic IR detectors, infrared radiation enters the Fresnel lens, after which it is focused on a sensitive pyroelectric element located on the optical axis of the lens

Passive IR detectors they receive infrared energy flows from objects and are converted by the pyro receiver into an electrical signal that enters through the amplifier and the signal processing circuit to the input of the alarm generator.

Passive infrared detectors are designed to detect a person who is within the sensitivity zone. The main task of the detector is to detect the infrared radiation of the human body. As can be seen from Figure 1, the thermal radiation of the human body is within the spectral range of electromagnetic radiation with wavelengths of 8-12 microns. This is the so-called equilibrium glow of the human body, the maximum radiation length of which is completely determined by temperature and for 37°C corresponds to approximately 10 microns. Exists whole line physical principles and related devices that are used to detect radiation in the specified spectral range. For PIR detectors, a sensitive element with an optimal sensitivity/cost ratio should be used. Such a sensitive element is a pyroelectric photocell.

Rice. 1. Spectral dependence of the intensity of the glow: the sun, a fluorescent lamp, an incandescent lamp, the human body and the transmission spectrum of a number of blocking visible light filters: silicon filter, coated silicon filter, filter with a cutoff wavelength of 5 µm and a filter with a cutoff wavelength of 7 µm.

The phenomenon of pyroelectricity consists in the occurrence of an induced potential difference on opposite sides of a pyroelectric crystal during its nonequilibrium short-term heating. Over time, electric charges from external electric circuits and the redistribution of charges inside the crystal lead to relaxation of the induced potential. From the above it follows:

interruption frequency (Hz).

Rice. Fig. 2. Dependence of the value of the pyroelement response signal on the interruption frequency of the recorded thermal IR signal.

1. For effective pyroelectric registration of thermal radiation, it is necessary to use a chopper with an optimal radiation interruption frequency of about 0.1 Hz (Fig. 2). On the other hand, this means that if a lensless design of the pyroelectric element is used, it will be able to register a person only when he enters the radiation pattern (Fig. 3, 4) and exits it at a speed of 1 - 10 centimeters per second.

Rice. 3, 4. Paired pattern shape corpsed pyroelectric element in horizontal (Fig. 3.) and vertical (Fig. 4.) planes.

2. To increase the sensitivity of the pyroelectric element to the temperature difference (the difference between the background temperature and the temperature of the human body), it is necessary to design it, maintaining the minimum possible dimensions, in order to reduce the amount of heat required for a given increase in the temperature of the sensitive element. The dimensions of the sensitive element must not be excessively reduced, as this will lead to an acceleration of the relaxation characteristics, which is equivalent to a decrease in sensitivity. There is an optimal size. The minimum sensitivity is usually around 0.1°C for a 1 x 2 mm pyro element, a few microns thick.

Rice. Fig. 5. Appearance of the sensitive element of the pyroelectric passive IR detector.

You can clearly formulate the conditions for detecting a person using an infrared detector. The infrared detector is designed to detect moving objects with a temperature different from the background value. Range of recorded movement speeds: 0.1 - 1.5 m/sec. Thus, the infrared detector does not register stationary objects, even if their temperature exceeds the background level (still person) or if an object with a temperature different from the background moves in such a way that it does not cross the detector's sensitive zones (for example, it moves along the sensitive zone). Of course, strictly speaking, the sensitive element does not register movement at all, it registers the temperature measurement in a single part of space, which is a consequence of a person's movement. It must always be remembered that the sensitive element detects movement not “on the detector”, but across. Getting rid of this disadvantage occurs due to the design of the lenses.

Naturally, the high sensitivity of the infrared detector is achieved by using a lens system for the concentration of incoming radiation (Fig. 6). In an infrared detector, the lens system performs two functions.

Rice. 6. Options for forming the directional diagram of IR detectors depending on the type of lens system.

First, the lens system serves to focus the radiation on the pyroelectric element.

Secondly, it is intended for spatial structuring of the detector sensitivity. In this case, spatial zones of sensitivity are formed, which ,e as a rule, they have the form of "petals", and their number reaches several tens. The object is detected every time it enters and exits sensitive areas.

Usually, the following types of sensitivity diagram are distinguished, which is also called a radiation pattern.

1). The standard one is fan-shaped in azimuth and multi-tiered in elevation (Fig. 6a).

2). Narrow beam - single- or double-beam long-range in azimuth and multi-tiered in elevation (Fig. 6b).

3). Curtain-like - narrowly focused in azimuth and fan-shaped in elevation (Fig. 6c).

There is also a circular pattern (in particular, for detectors installed on the ceiling of the room), as well as a number of others.

Consider options design beamforming systems (Fig. 7). This optical system can be either lens or mirror. The manufacture of a conventional lens system, taking into account the requirement for the formation of a spatially structured radiation pattern, is an expensive task, so conventional lenses are not used in passive infrared sensors. The so-called Fresnel lenses are used. In a conventional lens, a special spherical surface shape is used for directional light deflection (focusing), the lens material has an optical refractive index that is different from the refractive index of the environment. The Fresnel lens uses the phenomenon of diffraction, which manifests itself in particular in the deflection of a light beam when passing through a narrow slit. The Fresnel lens is made by stamping and is therefore cheap. The disadvantage of using a Fresnel lens is the inevitable loss of half of the radiation energy as a result of its diffraction deflection by the lens in a direction other than the direction to the pyroelectric element.

Rice. 7. Design options for security passive IR detectors: with a Fresnel lens and with a mirror focusing system.

The mirror lens is more efficient than the Fresnel lens. It is made of plastic mass by stamping followed by coating the structured surface with a reflective coating that does not change its properties over time (up to 10 years). Gold is the best plating. Hence the higher, approximately twice, the cost of passive infrared detectors with a mirror system compared to a lens one. In addition, detectors with a mirror system are larger than detectors equipped with Fresnel lenses.

Why use more expensive detectors with a mirror system for concentrating incoming radiation? The most important characteristic the detector is its sensitivity. Sensitivity is practically the same in terms of unit area of the detector's input window. This, in particular, means that if a passive infrared detector is designed with increased sensitivity, then they are forced to increase the size of the radiation concentration zone - the area of \u200b\u200bthe entrance window, and, therefore, the detector itself (the maximum sensitivity of modern passive infrared detectors allows detecting a person at a distance up to 100 meters). If we assume the presence of losses of the useful signal due to the imperfection of the lens, then it is necessary to increase the gain of the electronic circuit for processing the electrical signal generated by the sensitive element. Under the condition of the same sensitivity, the gain of the electrical circuit in a mirror detector is two times less than in a detector with a Fresnel lens. This means that in detectors with a Fresnel lens, there is a higher probability of false alarms caused by interference in electronic circuit. Quite often, both technologies are used together, so in the Astra-5sp detector. And the main zone is formed by zones of Fresnel lenses, the anti-sabotage zone directly under the detector is a small mirror made in a rather handicraft way. In general, the market for security detectors is filled with fairly cheap products, the price of which ranges from 300-900 rubles apiece with a significant advantage towards the lowest price. Naturally, in such conditions, it is not possible to talk about some kind of gilded mirrors.

Once again, let's return to the optical scheme of the detector. In addition to the lens system and the optical “cut-off” filter installed directly in the sensor housing, various optical filter elements (“white” filter, “black” mirror, etc.) are used to reduce false positives caused by various radiation sources. which minimize the incidence of extraneous optical radiation on the surface of the pyroelectric element.

The entrance window of most IR detectors is made in the form of a "white" filter. This filter is made of a material that scatters visible light, but at the same time does not affect the propagation of infrared radiation. Due to their low cost, cheap detectors use polyethylene similar in properties to those used for food bags, in more expensive ones they are milky in color, which transmits IR rays well, but a poorly visible spectrum, which is what we need.

Fresnel lenses are constantly being improved. First of all, by giving the lens a spherical shape that minimizes aberrations compared to the standard cylindrical shape. In addition, additional structuring of the radiation pattern in the vertical plane is applied due to the multifocal geometry of the lens: in the vertical direction, the lens is divided into three sectors, each of which independently collects radiation on the same sensitive element.

I will dwell in more detail on the structure of that part of the detector, which most electricians call the lens. This is a piece of polyethylene, on which rectangles of various sizes are squeezed out, inside of which certain concentric circles, or parts of them, are visible. In most cases, we see about 12-15 vertically elongated rectangles in the upper part, 5-6 more square-like rectangles in the middle part, and usually 3 almost square rectangles in the lower part. It is necessary to correctly understand that every of these rectangles is a Fresnel lens, so we have a matrix of lenses. In order to distinguish an intruder at the edge of the detection zone, and this is usually 10-12 meters, it must be divided into the number of elementary zones we need, which is what the upper set of rectangles does. The number of elementary zones will correspond to the number of rectangles. Naturally, in the middle part of the detector detection zone, it is no longer necessary to divide into such a number of elementary zones, and their number is already reduced to 5-6, and in the near zone - to 3. When considering a matrix of lenses, pay attention to an important feature - vertical the sides of the rectangles in different tiers are always shifted relative to each other. This was done specifically to be able to detect the intruder in the worst movement for the detector "to the detector". Even if the intruder accidentally hit exactly in the middle of the elementary sensitive zone and moves directly to the detector, then in another tier he will not be able to get into the middle of the elementary zone in the same way and will be detected by it. When placing the detector, it must be taken into account that its maximum detective abilities precisely when the intruder moves across sensitive zones.

Very relevant is the problem of counteracting the physical shielding of the detector, which comes down to installing a screen in front of it that overlaps its “field of view” (the so-called “masking”). Technical means of counteracting masking constitute a system antimasking detector. Some detectors are equipped with built-in IR LEDs. If an obstacle appears in the detection zone of the detector, and therefore in the area of the LEDs, the reflection of the LED radiation from the obstacle is perceived by the detector as an alarm signal. Moreover, periodically (in existing models - once every 5 hours) the detector self-tests for the presence of reflected radiation from IR LEDs. In the event that the necessary signal does not appear at the output of the electrical circuit during the self-test, the alarm generation circuit is triggered. Detectors with functions antimasking and self-testing are installed at the most critical facilities, in particular, where it is possible to counteract the operation of the security system.

Another way to increase the noise immunity of the detector is the use of a quadratic sensitive pyroelement in conjunction with the use of microprocessor signal processing. Different firms solve the problem of creating a quadratic element in different ways. For example, the OPTEX company uses two conventional dual pyroelements located side by side. The main task of the system is to isolate and “screen out” events caused by the simultaneous illumination of both pyroelements (for example, headlights) or electrical interference.

Quite a lot of companies use a special design of a quad pyro receiver, where four sensitive elements are located in one housing.At the same time, pyroelements located both in the horizontal plane and in the vertical one are turned on in the opposite direction. Such a detector will not respond to small animals (mice, rats), which are often found in warehouses and are one of the causes of false alarms (Fig. 8). The use of a bipolar connection of sensitive elements in such a detector makes it impossible for "noise" false alarms.

ADEMCO is so confident in the perfection of the quadratic detector developed by it that it announced the payment of a bonus if the owner of the detector fixes its false operation.

Another precaution is the use of conductive film coatings applied to the inside surface of the entrance window to counteract RF interference.

An effective method of increasing the noise immunity of detectors is the use of the so-called "double technology", which consists in using a combined detector that implements passive infrared and active radio wave (sometimes ultrasonic) principles of operation. Such detectors will be discussed in the following lectures.

Rice. 8. The operation of a multi-channel system for selecting noise pulses on the example of the operation of a quadratic security passive IR detector.

Due to the principle of detection, it is very difficult for such detectors to detect an intruder if the ambient temperature approaches the temperature of the human body. In such cases, the detector simply goes blind, and for our southern region, a temperature of 35-40 degrees in summer is not at all uncommon, especially in closed, unconditioned rooms with insufficiently insulated roofs and walls. To combat this problem, a thermal compensation. The essence of its work lies in the fact that when the temperature in the room approaches the critical one (37 degrees Celsius), the detector increases sensitivity stepwise (usually by an order of magnitude). Of course, this reduces its noise immunity, but it allows you to detect an intruder in these extreme conditions. When the temperature drops, the detector returns sensitivity to normal.

We examined the basics of operation and design of passive infrared security detectors. In general, all constructive tricks used by certain companies have one goal - to reduce the likelihood of a false alarm, since a false alarm leads to unjustified costs for responding to an alarm, and also causes moral damage to the owner of the protected property.

Detectorsare constantly being improved. At the present stage, the main directions for improving detectors are to increase their sensitivity, reduce the number of false alarms, differentiate moving objects on the basis of authorized or unauthorized presence in the detection zone.

As a source of electrical signal, each sensitive pyroelectric element is also a source of random noise signals. Therefore, the problem of minimizing fluctuation interference, which can be solved by circuitry, is topical. Various noise reduction methods are used.

Firstly, electronic discriminators of the input signal are installed in the detector for the upper and lower levels, which minimizes the frequency of interference (Fig. 9).

Rice. 9. Threshold system for two-way limiting of the noise signal level of a security passive IR detector.

Secondly, the mode of synchronous counting of pulses coming from both optical channels is applied. Moreover, the circuit is designed in such a way that a useful optical signal at the input leads to the appearance of a positive electrical pulse in one channel and a negative one in another. The subtraction scheme is applied at the output. If the source of the signal is a noise electrical signal, it will be identical for two channels and at the output the resulting signal will be missing. If the signal source is an optical signal, then the output signal will be summed.

Third, the pulse counting method is applied. The essence of this method is that a single object registration signal does not lead to the formation of an alarm, but sets the detector to the so-called "pre-alarm state". If within a certain time (in practice it is 20 seconds) the object registration signal is not received again, the pre-alarm state of the detector is reset (Fig. 10). This method must be used with caution and only when warranted. It must be remembered that the detector may not have a chance to fix the second impulse, and it will rest peacefully covered with a cardboard box.

Rice. 10. Operation of the pulse counter system.

The remarkable property of forming a detection zone with a matrix of Fresnel lenses allowed manufacturers to create a unified detector design and change its properties by replacing the matrix. Thus, the same detector can be made voluminous, it is possible to create a “long beam” zone - it sees far, but narrowly, it is possible to create a detector - a “curtain”, with which we can cut off the necessary parts of the object using a detection zone similar to a curtain.

As a rule, all detectors require a 12 V power supply. direct current. The current consumption of a typical detector is in the range of 15 - 40 mA. The alarm signal is generated and transmitted to the security control panel by means of an output relay with normally closed contacts.

The use of solid-state relays instead of conventional relays also made it possible to reduce energy consumption. Let me remind you that these detectors are passive, which also allows you to have a minimum current consumption. Like most security detectors, PIR detectors are recoverable, i.e. when an intruder is detected, it will go into the "alarm" state, in the absence of further movement registration, it will be restored to the "normal" state. Usually, for ease of maintenance, the detector has a built-in red LED that signals the "alarm" state, but can also transmit other additional messages.

For the normal placement of the detection zone in space, it is necessary to take into account the detector installation height recommended by the manufacturer, which is usually 2.2-2.5 meters for a wall-mounted version. Let me also remind you that reorientation of the detector (sideways, upside down) is not allowed.

When choosing a detector, it must be remembered that they have different temperature ranges, and if you install a detector that operates up to 0 degrees in an unheated room, then you can expect problems in operation during frost in winter.

The industry produces detectors for installation indoors, as well as outdoors; the latter have the appropriate climatic design.Typical service life of passive infrared detectors is 5 - 6 years.

Detector examples

With a detection zone of the "long beam" type: Astra-5 isp. V, Photon-10A, Photon-15A, Photon-16.

With a detection zone of the "curtain" type: Astra-5 isp. B, Astra-531 isp. IR, Ikar-Sh, Ikar-5B, Photon-10B, Photon-10BM, Photon-15B, Photon-16B, Photon-20B, Photon-22B, Photon-Sh, Photon-Sh-1, Photon-Sh2.

With volumetric detection zone: Astra-5 isp. A, Astra-5 isp. AM, Astra-511, Astra-512, Astra-7 isp. A, Astra-7 isp. B, Photon-9, Photon-9M, Photon-10, Photon-10M, Photon-10M-01, Photon-12, Photon-12-1, Photon-15, Photon-16, Photon-17, Photon-19, Photon-20, Photon-21, Photon-22, Ikar-1A, Ikar-2/1, Ikar-5A, Ikar-7/1.

Active optical-electronic detectors.

Linearoptoelectronic detectors (active IR detectors), as a rule, have a two-block design and consist of an emitter unit (BI) and a photodetector unit (BF), forming an optical system. The emitter generates a stream of infrared radiation (infrared beam) with specified characteristics, which falls on the receiver. The appearance of an optically opaque object in the detection zone of the detector causes an interruption of the IR beam (or a decrease in its power) that enters the receiver, which analyzes the magnitude and duration of this interruption and, in accordance with the specified algorithm, generates an alarm notification by changing the resistance of the contacts connected to the alarm loop. There are also detectors that have a single-block design, the optical system of which consists of an emitter and a photodetector combined in one housing, as well as a reflector (reflector). The input windows of the BI and BF are usually closed with special filters (sometimes these filters are made as one piece with the cover of the detector housing). The scheme of the active IR detector is shown in Figure 11.

The advantage of active IR detectors is that they detective the ability does not depend on the characteristics of the thermal radiation of a person (intruder). They are also insensitive to changes in the characteristics of the thermal radiation of surrounding objects (background) and the resulting thermal interference, which is very important when operating in open areas.

Figure 11 - Diagram of an active IR detector

The disadvantages of active IR detectors include their ability to form only a linear detection zone, which leads to a narrow scope. In part, this problem can be solved by organizing a surface detection zone through the use of detectors that form several IR beams, or by building an IR barrier from several detectors. But at the same time, the size of the detection zone for the first option will be small, and the second option will require an increase in financial costs. The disadvantages include sensitivity to optical illumination.

Recently, some manufacturers have been trying to create an active security detector using an infrared laser. So, the Japanese company Optex has recently launched a detector that uses the principle of scanning the surrounding space with a laser beam.

Main functional characteristics active IR detectors and their impact on the use and tactics of protection

Active IR detectors form a linear detection zone. They can be used to organize the first line of protection of objects (blocking of extended engineering fences (fences), windows or doors outside the building, gates, ventilation shafts and channels, etc.). Because active infrared detectors form a linear detection zone, their use will be influenced by the shape of the protected object, depending on the characteristics of the landscape and the object itself. Protected objects must be straight, otherwise, the object is divided into several straight sections, to block which a separate detector is used (see Figures 12, 13).

Figure 12 - Incorrect use of an active IR detector

Figure 12 shows the incorrect use of an active IR detector. In zones A and B, an intruder can enter through a guarded fence. At the same time, in zone B, the detection zone of the detector is located outside the protected facility, where there is high probability its accidental overlap (swaying tree branches, the actions of bystanders, etc.), which will lead to the formation of a false alarm notification.

Figure 13 - Scheme of protection of an object of complex shape

Figure 13 shows an exemplary scheme for protecting an object of complex shape with the help of several detectors. The breakdown of the object into sections should be done in such a way that the intruder could not penetrate the object without blocking the IR beam, i.e. the maximum distance between the fence sheet and the IR beam (an imaginary line between the BI and the BP) should be less than the dimensions of a person (approximately 300 - 350 mm).

The main functional characteristics of an active IR detector are the maximum operating range, safety factor, sensitivity and noise immunity.

The maximum operating range is the maximum possible distance at which the emitter and receiver of the detector can be separated, provided that it complies with the requirements of the national standard.

The safety factor is the maximum value of the reduction in the flow of infrared energy, which does not lead to the formation of an alarm notification. This coefficient characterizes the resistance of the detector to meteorological factors (rain, snowfall, fog). The minimum allowable safety factors depend on the operating range and are given in the national standard. Because there is no precipitation in the premises, the requirements for the safety factor of detectors intended for indoor operation are significantly lower than those for detectors intended for operation on outdoors.

Specific values of the maximum operating range and safety factor for each detector model are set by the manufacturer.

To ensure the possibility of use on various objects, most modern active IR detectors have the ability to adjust the range. As a rule, the adjustment is discrete, each of its values corresponds to a certain range of range. It is not allowed to operate the detector if the actual range does not match the range set during the adjustment. If the actual range exceeds the set one, the safety factor may turn out to be insufficient, which, in the presence of precipitation (intense snow, rain, dense fog), may lead to a malfunction of the detector (manifested in the form of a false alarm notification and the impossibility of arming). If the actual range is below the set power of the IR radiation falling on the receiver, it will be excessive, which in some cases may lead to the intruder being missed. Excessive signal power is also due to the fact that active IR detectors have a minimum range. The distance between BI and BF should not be less value specified in the operational documentation attached to the detector.

The sensitivity of an active IR detector is the duration of the interruption of the infrared beam, above which the detector should generate an alarm notification. The minimum allowable sensitivity value for detectors operated in open areas is regulated by the national standard and is 50 ms.

This value is determined taking into account the anthropometric characteristics of a person and corresponds to the intruder crossing the detection zone of the detector by running with maximum speed. Modern detectors provide discrete sensitivity adjustment up to 400 - 500 ms.

It is recommended to set the sensitivity value taking into account the most probable time the intruder stays in the detection zone, which depends on its size and movement speed. For example, if the detector is installed in an open area, where an intruder will be able to run up and cross the zone at high speed, high sensitivity (50 ms) should be set. If the intruder does not have the opportunity to take off and move at high speed (for example, when blocking a narrow space between two fences), the sensitivity value can be set in the range of 100 - 200 ms. If the intruder is forced to stay in the zone for a sufficiently long time, for example, when crawling over a blocked area or climbing over a fence (fence), the sensitivity value can be set in the range of 400 - 500 ms. The correctness of the choice of the sensitivity value must be checked after installing and configuring the detector on the object by making test crossings of the zone in the most probable ways and at the highest possible speed. After each crossing of the detection zone, the detector must generate an alarm notification. Except in justified cases, it is not recommended to set the maximum sensitivity (50 ms), because. this reduces the noise immunity of the detector.

Interference immunity is the duration of the interruption of the infrared beam, in the absence of which the detector does not generate an alarm notification. The minimum allowable value of noise immunity for detectors operated in open areas is regulated by the national standard and is 35 ms. This value is determined taking into account the size and speed of movement of the most likely obstacles, such as falling leaves, flying birds, etc.

In modern domestic detectors, the change in noise immunity occurs automatically simultaneously with the change in sensitivity in the process of its adjustment. An increase in the noise immunity of the detector is facilitated by the use of a dual (synchronized) IR beam in it. The relationship between sensitivity and noise immunity for modern domestic active IR detectors is shown in Table 1.

Table 1

Parameter	Meaning
Sensitivity, ms
Noise immunity, ms

Influence of external factors on the operation of active IR detectors and recommendations for its reduction

1) temperature factor. The ambient temperature has a negative impact on the performance of the detector, if its value exceeds the allowable values of the operating temperature set for this detector. To reduce the possibility of overheating of the detector, if possible, avoid installing it in places where it will be exposed to direct sunlight for a long time, and also use protective visors. For use in areas where winter time very low temperatures are often observed (minus 40 ° C and below), it is necessary to choose detectors that have built-in automatic heating of the board and optics. The lower value of the operating temperature range for modern domestic detectors is minus 40 °С, in the presence of built-in heating, it drops to minus 55 °С. If the air temperature has dropped below the admissible values of the detector, it must be taken into account that it may not detect the intruder, it is advisable to organize the protection of the object by patrolling.

2) Optical flare. The reason for high illumination can be both the sun and sources of artificial lighting. The presence of a light detector at the input window of the BF, the actual value of which exceeds the norms established in the national standard (more than 20,000 lux from natural light and light sources powered by DC sources, and 1000 lux from light sources (including fluorescent lamps) powered by AC mains) can cause false alarms or skip the intruder. To exclude the influence of this factor on the operation of the detector, it must be installed in such a way that direct sunlight does not fall on the BF entrance window (this is especially important during sunset or sunrise, when various protective visors are ineffective) and radiation from powerful lighting devices (spotlights, powerful fluorescent lamps, etc.). Most of the active IR detectors included in the “List…” today are resistant to natural light up to 30,000 lux.

3) Precipitation. Atmospheric precipitation has a negative effect on the safety factor of the detector due to the attenuation of radiation due to scattering by water drops or snowflakes. They can also cause moisture to appear in the housings of the detector blocks, which can cause the loss of its performance. In winter, the input windows of the detector units may also become iced. The safety factor of modern detectors, as a rule, allows them to function properly in the presence of precipitation, but in the case of their special intensity, a malfunction of the detector may occur (manifested in the form of a constant generation of an alarm notification and the impossibility of arming). In this case, you should organize the protection of the object by patrolling. To reduce the harmful effects of precipitation, protective visors can be used, more frequent maintenance (cleaning the entrance windows from ice and snow) of the detector should be carried out. It is necessary to use detectors with a higher degree of protection of the shell (not lower than IP54 according to GOST 14254), carefully seal the inlet technological openings in the block housings during installation. If the detector is installed at a low height from the ground or other surface (for example, directly above the fence), a gradually increasing layer of snow (snowdrift) can block the detection zone of the detector, which will cause a constant generation of a false alarm. The detection zone of the detector can also be blocked by the formed icicles if it is located under any protruding structures and their elements. In order to prevent a malfunction of the detector, it is necessary to clear the snow accumulating in the detection zone and remove the formed icicles in a timely manner. If the detector is installed along the upper edge of the fence, it is recommended to move it from the axis of the fence into the object.

4) Electromagnetic interference(EMP). The source of EMF that can affect the operation of the detector can be both operating high-power electrical equipment and atmospheric electrical discharges (thunderstorm). For outdoor operation, detectors should be used that have resistance to EMF according to GOST R 50009 (electrostatic discharge, electromagnetic field, electrical impulses in the power supply circuit) of at least 3 degrees. When installing detectors outdoors, it is necessary to lay long connecting lines exposed to EMF. To reduce the effect of EMF on the operation of the detector, it is necessary to lay all connecting lines in metal hoses (steel pipes) and use grounding.

5) Changing the position in space of structures on which the detector blocks are fixed. These changes can be both natural and man-made. The reason for them may be, for example, vibration due to the operation of any mechanisms or the movement of heavy vehicles, seasonal ground movements, repair and other work carried out in the immediate vicinity of the detector installation site. Their consequences may be false positives and a decrease in the safety factor. To prevent the influence of this factor on the operation of the detector, it is necessary, if possible, to install it on bases that are not subject to vibration, deformation, and have a stable foundation ( bearing walls capital buildings, etc.).

6) The presence of solid fine particles in the air. These particles can be of both natural (dust, plant pollen) and technogenic (dust, soot, etc.) origin. Their settling on the input window of the detector leads to a decrease in the safety factor. To combat this phenomenon, in areas with a high content of dust or soot in the air, more frequent maintenance of the detector should be carried out. Operational features active IR detectors.

Power supply of active detectors, as a rule, is allowed to be carried out from a DC source with a rated voltage of 12 or 24 V. For power supply of detectors operated in open areas (especially with a large length of power loops), it is recommended to use sources with a rated voltage of 24 V. Power supply for built-in heating (if any), as a rule, is carried out from a separate source connected to terminals specially designed for this purpose.The output power of the sources must match the load.

Features of the organization of the IR barrier

The interval between the detectors should be chosen in such a way that the intruder does not have the opportunity to crawl between the IR beams without blocking them. For outdoor applications, a spacing of about 350 mm can be recommended. To organize an IR barrier, you can use detectors that have several operating frequencies. This is necessary to exclude the influence of the radiation of one detector on the operation of the neighboring one. If it is necessary to use detectors in the barrier in excess of the number of operating frequencies, they must be installed in such a way that the IR beams of the detectors operating at the same frequency are directed towards each other (Figure 14). In the same way, it is possible to organize a two-beam barrier of detectors having one operating frequency.

Figure 14 - Example of barrier IR detectors operating at the same frequency

If it is necessary to create an IR barrier in the horizontal plane, the detectors must be installed in such a way that the radiation of the same operating frequency of closely located PIs is multidirectional and cannot simultaneously fall on the input window of one BP (Figure 15).

Figure 15 - An example of an IR barrier in the horizontal plane

Setting the parameters of the detector, necessary for operation at each specific object, is carried out either using switches or by programming. The process of programming parameters is described in the operational documentation attached to the detector. After installing the detector on the object and connecting the power supply, it is necessary to adjust the relative position of the emitter and detector receiver. Coarse adjustment is carried out visually by approximate alignment of their optical axes or according to the indications of the IR radiation indicator (if this indicator is available). In some models of detectors (for example, IO209-32 "SPEK-1115"), a special optical sight is provided for this purpose. After completion of coarse adjustment, it is necessary to perform adjustment (fine adjustment) of the blocks. It is carried out by smoothly turning the block in different directions at a small angle in the horizontal and vertical planes using the adjustment devices (screws or flywheels) provided for by the design of the detector. The adjustment process is controlled, depending on the specific detector model, either by the readings of a voltmeter connected to a special connector, or by a change in the built-in light indication. Adjustment is considered completed at the maximum readings of the voltmeter or if there is a light indication, the type of which is indicated in the operational documentation. ATTENTION. Alignment of the detector blocks ensures the presence of BF on the input window required power IR radiation, as well as achieving the maximum safety factor, is a necessary and mandatory procedure, even if, after a rough adjustment, the detector goes into standby mode and is able to generate an alarm notification when crossing the detection zone.

Remote operation control is designed to check the detector's performance from the central monitoring console. It is carried out by short-term switching of the output specially designed for this purpose and the positive output of the power supply. As a result, a short-term interruption of the BI radiation occurs, after which the detector must issue an alarm notification. This feature requires additional wiring, but may be useful when perimeter security long or difficult access to the detector (for example, in winter). If the detector is installed in such a way that its detection zone is directed along an extended surface (fences, walls, etc.) .P), the effect of re-reflection may appear, which consists in the fact that, in addition to direct IR radiation, re-reflected radiation will also fall on the input window of the BF (Figure 16). As a result, with sufficient power re-reflected radiation, the detector will not generate alarm notifications when the main one is blocked. This effect can also manifest itself during low-intensity precipitation, when IR radiation is reflected from snowflakes and water drops.

Figure 16 - Reflection effect

To eliminate the negative impact of the reflection effect in modern domestic detectors, it is possible to turn on the so-called. “intelligent signal processing mode”, the essence of which is that the detector generates an alarm notification when the IR radiation power at the BF input window decreases by about 70%.

In the domestic market, active IR detectors are currently represented mainly by the products of the Russian company SPEC CJSC (St. Petersburg), Japanese firms Optex and Aleph, German Bosch and some others.

To date, only detectors manufactured by CJSC "SPEK" fully comply with the requirements of domestic national standards and ETT. Below are recommendations for their selection for the protection of various objects, taking into account the main features and characteristics. It should be noted that the design features of active IR detectors, especially those intended for operation in open areas, determine their high cost. Therefore, the use of most of them will be most appropriate at fairly important facilities.

The selection of single beam detectors (or dual synchronized IR beam) is generally based on the maximum operating range. It is not advisable to use a detector with a maximum operating range that significantly exceeds the actual size of the protected object. For operation in areas where very low temperatures are often observed in winter (minus 40 ° C and below), it is necessary to choose detectors that have built-in automatic heating of the board and optics. Installation, connection, configuration and operation of the detectors must be carried out in strict accordance with the attached operational documentation. Some detectors can also be used indoors. In this case, their maximum operating range is increased due to lower safety factor requirements, which should be reflected in the operational documentation. Each active IR detector included in the list is assigned a symbol of the type "IO209-XX / U", where "I" means the type of product (detector), "O" - scope (security), "2" - characteristic of the detection zone ( linear), "09" - the principle of operation (optical-electronic), "XX" - the serial number of the development, registered in the prescribed manner, through the slash "Y" - the serial number of the design modification (if there are several modifications).

Figure 17 - IO209-16 "SPEK-7"

IO209-16 "SPEK-7".The multibeam detector is produced in two versions (modifications) IO209-16/1 "SPEK-7-2" (forms 2 beams with an interval of 350 mm) and IO209-16/2 "SPEK-7-6" (forms 6 beams with an interval of 70 mm). The emitters and photodetectors are mounted in single housings (the so-called KI and KF columns). The detector is recommended to be used to protect gate openings, gates, blocking access to windows and doors of the building from the outside. At the same time, IO209-16/2 "SPEK-7-6" is able to detect a hand extended through the detection zone. Both versions of the detector have an operating range of 0.4 to 15 m (outdoors), 4 sensitivity settings. It is possible to use up to 5 detectors in the IR barrier. In this case, the CIs are combined by a synchronization line. CFs can be both synchronized and each work with its own settings. The maximum length of the synchronization line between adjacent CIs or CFs is no more than 10 m. Synchronization allows you to save money by laying a smaller number of loops. It is possible to set the number of IR beams, the simultaneous intersection of which is necessary to generate an alarm notification, which increases the detector's resistance to crossing the detection zone by small animals, birds, etc. The detector can also be used indoors.

IO209-17 "SPEK-8" The detector has a double infrared beam in the horizontal plane, 4 operating frequencies, 4 sensitivity values, built-in heating. The range of the detector is from 35 to 300 m. The detector is recommended for blocking straight sections of long perimeters, incl. in areas with cold climates.

Figure 18 - IO209-17 "SPEK-8"

Figure 19 - IO209-22 "SPEK-11"

IO209-22 "SPEK-11"The maximum operating range is 150 m (outdoors). The detector has 1 IR beam, 2 operating frequencies, 2 sensitivity values. This detector is intended for use in explosive zones of class 1 and 2 of premises and outdoor installations in accordance with GOST R 52350.14 (classes B-Ia, B-Ib, B-Ig according to PUE) and other regulatory documents regulating the use of electrical equipment in explosive zones. Explosion-proof design of the "flame-proof shell" type. Explosion protection marking 1 Ex d IIB T5 X. The detector can also be used indoors. Application on other objects is impractical due to the high cost.

IO209-29 "SPEK-1112" Detector with two horizontal out of sync IR rays. Due to the presence of two output relays, the detector allows you to determine the direction of the EA crossing by the intruder (when the beams cross in one direction, one relay opens, and when the beams cross in the other direction, the second one). Operating range - from 10 to 150 m. The detector has built-in heating, 4 operating frequencies, 2 sensitivity values. Recommended for the protection of various objects, incl. in areas with cold climates.

Figure 20 - IO209-29 "SPEK-1113"

IO209-29 "SPEK-1113" The detector has a single block design with a reflector, 5 operating frequencies, 4 sensitivity values. Operating range - from 5 to 10 m (outdoors). There is no built-in heating. It is recommended to use for blocking gate openings, gates, air duct outlets, ventilation shafts and other small objects. Due to the relatively low cost, it would be advisable to use the detector, incl. for the protection of ordinary objects, individual housing construction objects, etc. The detector can be used indoors.

Figure 21 - IO209-32 "SPEK-1115"

IO209-32 "SPEK-1115"It is produced in four versions, differing in the maximum working range and the presence of built-in heating:

a) IO209-32/1 "SPEK-1115" has a range of 1 to 75 m;

b) IO209-32/2 "SPEK-1115M" has a range of 1 to 75 m and built-in heating;

c) IO209-32/3 "SPEK-1115-100" has a range of 1 to 100 m;

d) IO209-32/4 "SPEK-1115M-100" has a range of 1 to 100 m and built-in heating.

detectorhas a dual IR beam in the vertical plane, 4 operating frequencies, 4 sensitivity values. Recommended for the protection of various objects, incl. in areas with a cold climate (for versions with the letter "M").

IO209-29 "SPEK-1117"This detector is a simplified modification of the "SPEK-1115" detector and has a lower cost, due to which it will be advisable to use it, incl. and for the protection of ordinary objects, individual housing construction objects, etc. The detector has a double infrared beam in the vertical plane, 1 operating frequency, 2 sensitivity values.

Imported detectors present on the domestic TCO market often do not comply with the current national standard and ETT in terms of resistance to impact low temperatures environment and switching parameters of output relays. Also, foreign manufacturers in the technical characteristics of their detectors do not give the value of the safety factor.

A list of regulatory and technical documentation, the requirements of which must be taken into account when studying this topic.

1. R78.36.026-2012 Recommendations. The use of technical detection tools based on various physical principles for the protection of fenced areas and open areas.

2. R78.36.028-2012 Recommendations. Technical means of detecting intrusions and threats various kinds. Features of selection, operation and application depending on the degree of importance and danger of objects.

3. R78.36.013-2002 - “Recommendations. False alarms of technical means of protection and methods of dealing with them.

4. R78.36.036-2013 " Toolkit on the selection and use of passive optical-electronic infrared detectors”.

5. R78.36.031-2013 "Survey of objects, apartments and MHIG accepted as a centerlysed security."

6. R78.36.022-2012 "Methodological guide for the use of radio wave and combined detectors in order to increase the detecting ability and noise immunity."

7. GOST R 50658-94 Alarm systems. Part 2. Requirements for burglar alarm systems. Section 4. Ultrasonic Doppler detectors for enclosed spaces.

8. GOST R 50659-2012 Doppler radio wave detectors for indoor and outdoor areas. General technical requirements and test methods.

9. GOST R 54455-2011 (IEC 62599-1:2010) Intrusion alarm system. Test methods for resistance to external influencing factors, modified in relation to the international standard IEC 62599-1:2010 Alarm systems. Part 1: Environmental test methods.

10. GOST R 50777-95 Alarm systems. Part 2. Requirements for burglar alarm systems. Section 6. Passive optical-electronic infrared detectors for enclosed spaces.

11. GOST R 51186-98 Passive burglar alarms for blocking glazed structures in enclosed spaces. General technical requirements.

12. GOST R 54832-2011 Security point detectors magnetic contact. General technical requirements.

13. GOST R 52434-2005 Optoelectronic active security detectors. General technical requirements.

14. GOST 31817.1.1-2012 Alarm systems. Part 1. General requirements. Section 1. General Provisions.

15. GOST 52435-2005 Technical means of security alarms. Classification. General technical requirements and test methods.

16. GOST R 52551-2006 Security and safety systems. Terms and Definitions.

17. GOST R 52650-2006 Combined radio wave and passive infrared security detectors for enclosed spaces. General technical requirements and test methods.

18. GOST R 52651-2006 Linear radio wave security detectors for perimeters. General technical requirements and test methods.

19. GOST R 52933-2008 Surface capacitive security detectors for rooms. General technical requirements.

20. GOST R 53702-2009 Vibrating surface security detectors for blocking building structures of enclosed spaces and safes.

21. GOST 32321-2013 Shock-contact surface security detectors for blocking glazed structures in enclosed spaces.General technical requirements.

22. The list of technical security equipment that satisfies the "Unified technical requirements to centralized surveillance systems intended for use in private security units" and "Unified technical requirements for object security subsystems intended for use in private security units".

23. www.ktso.ru

24. www.guarda.ru

Questions for self-examination.

1. What is a sensitive element in PIR detectors?

2. Why is the detection zone of the PIR detector divided into tiers?

3. What are the main types of detection zones for PIK detectors?

4. What type of detection zone does the active infrared detectors we have reviewed have?

5. Give an example of an active infrared detector.

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