The best infrared thermometers according to customer reviews. Optoelectronic detectors Other protection elements of IR detectors

The most common motion detectors that are used in security- fire alarm, are optical-electronic detectors.

According to the principle of detecting movement, they are divided into two groups: passive catching objects and active ones - they produce their own radiation and determine the presence of a moving object by its change.

In addition, such detectors classify the configuration of the scanned area, they are:

Volumetric;
Surface (curtain);
Linear (beam).

The devices are used to organize security inside the premises, that is, as a second line of defense. However, a device with a linear and surface detection method can also be used to control the crossing of the perimeter.

The main disadvantage of passive surface optical-electronic detectors is that they are triggered when the intruder has already entered the premises. That is, they cannot perform early intrusion detection.

Passive devices, both volumetric and linear, are characterized by a small distance of the controlled zone, depending on the power of the model, 10-25 m. Therefore, they are usually used to protect small and medium-sized premises in a set of several pieces per cable. To organize the protection of buildings with large areas, it is recommended to use active optical-electronic devices.

Sensitivity The sensor of the optical-electronic detector is a pyro-receiver. It is an infrared device. Depending on its intensity, the pyro receiver generates a different number of electrical impulses, which are processed by an electronic logic unit. Most modern models are equipped with two sensitive sensors, which significantly reduced the number of false positives.

Active optical-electronic security detectors

The scope of these devices is quite diverse. They can be used to monitor windows and doorways, storefronts or outside perimeters. Depending on the type of construction, two types of active detectors are distinguished:

Single-position - in the body of one device is placed both the emitter and the receiver of reflected radiation. Operation occurs in the event of a change in the intensity or frequency of the reflected radiation flux.
Two-position - consist of two modules, one of which is an emitter, the second is a radiation receiver. The operation is carried out due to the interruption of the reception of the studied stream.

As a rule, the detection zone has the appearance of a barrier - "curtains", which is formed by one or more beams located in a vertical or horizontal plane. Various models may have different amount children of rays, their sizes and configuration. In this case, the mutual arrangement of the rays may not necessarily be parallel. However, the receiver and emitter of each particular beam must be configured so that they do not intersect.

To ensure highly efficient uninterrupted operation of active optical-electronic detectors, it is necessary to adhere to certain rules during their installation and operation:

Devices, both single-position and two-module, must be installed on non-deformable, durable building structures that exclude the possibility of excessive vibrations;
The receiver of on-off devices must be placed in such a way as to exclude the possibility of the influence of intense artificial and natural lighting on the photocells. Constant exposure to visible spectrum light on the receiver lens can lead to premature burnout of the LEDs or photodiodes and, as a result, the speaker of the device. Partially, this problem can be solved by using special light filters that do not transmit radiation in the visible and ultraviolet spectrum. However, in addition to the high cost of these devices, they somewhat reduce the sensitivity of the device.
When installing both sources and receivers of IR radiation, it is necessary to exclude the possibility of passing various foreign objects less than 0.5 m from the passing beam.

Devices based on passive IR sensing have become more widespread, as they are cheaper devices, and due to wide choice(systems of Fresnel lenses) the user quickly receives various forms scanning zones, which facilitates the creation of reliable security systems in buildings with a complex layout interior spaces. Passive IR motion detectors are used in systems alarm and ACS for protection:

Industrial and public buildings, apartments and private households;
Separate elements of structures most vulnerable to penetration: window openings and external doors, as well as walls, shop windows, ceilings and floors;
Perimeters land plots and fences;
Separate material assets- expensive art objects or unique devices.

A passive optical-electronic detector forms a scanning area consisting of narrow alternating sensitive and inactive zones in the form of a fan, multidirectional in one plane. The mutual arrangement of the rays in space can be different: horizontal, vertical, in several rows or assembled into one narrow beam. The shape of scanning zones is conditionally divided into 5 main types:

A wide-angle surface with one tier of rays emanating from one source - a "fan";
Wide-angle surface with narrow beams oriented in the same plane - "Curtain";
Narrow beam - "beam barrier";
Single-tier surface panorama;
Multi-tiered volume.

When installing passive optical-electronic detectors, the following recommendations must be observed:

Do not install the IR detector above convection heat sources;
Do not point the sensitive area of the device at spotlights, fan heaters, powerful incandescent lamps and other devices that can cause a rapid increase in the local temperature background;
Protect the device from excessive influence solar radiation;
Refrain from being in the critical detection zone of cabinets, curtains and other types of partitions that can create a “dead” controlled zone.

Brief overview of popular models

Detector security surface optical-electronic photon-sh— forms a curtain-type detection zone. It is used to control penetration into the premises through window and door openings. Detection range 5m, curtain width 6.8m, viewing angle 70°.

Detector security optical-electronic pyron 4 B- equipped with a two-sensor pyro receiver. Type of detection zone "curtain", range 10m, viewing angle 70°. It has a fine adjustment of sensitivity, is resistant to radio interference and external illumination.

AX-100TF active dual beam detector- used to control extended sections of the outer perimeter. Usually used in pairs, the fixtures are stacked on top of each other to form a barrier of four restrictive beams. There is a choice of four channels of carrier frequencies of the generated beams.

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-mentioned 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).

Passive IR detectors receive infrared energy flows from objects and are converted by a pyro receiver into an electrical signal, which is fed through an amplifier and a signal processing circuit to the input of an 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 design of the Fresnel lens, passive optical-electronic IR detectors have different geometric dimensions of the controlled space and can be either with a volumetric detection zone, or 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:

low price

Typically, each segment of a Fresnel lens forms its own beam pattern. Usage modern technologies The production of lenses makes it possible to ensure almost constant sensitivity of the detector 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. AT recent times 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. Effects such as heat flows, which are the result of heating the electrical components of the sensor, the ingress of insects on sensitive pyroelectric receivers, 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 very long distance detection.

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 alarms. In the differential circuit, the signal of one pyroelectric element is subtracted from another, which makes it possible to significantly suppress interference associated with a change 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, simple sensors use a pulse counting method 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 25°С…35°С the sensitivity of the pyrodetector decreases due to the decrease in the thermal contrast between the human body and the background; with a further increase in temperature, the sensitivity increases again, but with 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 for better selection him against the background of interference. 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 signal processing methods are used. It should be borne in mind that special signal processing allows ignoring animals only if their total weight does not exceed 7 ... 15 kg, and they can approach the sensor no closer than 2 m. will 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, configure and Maintenance. Detectors of this type can be installed both on a flat surface bearing wall as well as in the corner of the 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 of the device, 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. However, in some cases it is not necessary a large number sensors 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.

General principle the use of IR sensors - the rays of the sensitivity zone must 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 indoor doors open inwards, the possibility of masking the intruder should be taken into account. open doors. 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 their operation is less affected by existing pieces of furniture.

3. Detectors with a surface detection zone (Fig. 4) are used to protect the perimeter, for example, non-permanent walls, door or window openings, and can also be used to limit the approach to any 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. Although modern IR sensors have a high degree protection from these influences, it is still advisable to adhere to the following recommendations:

sun rays

bright light

sodium lamps

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

A special place in the incorrect or incorrect operation of passive optoelectronic IR detectors is occupied by installation errors during the installation of 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.

Right choice passive optical-electronic IR detector and its installation location - 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 burglar alarm systems, detectors that have an optoelectronic principle of operation are widely and willingly used by installers. Let's see how they work, and also consider the advantages, disadvantages and scope of these devices.

The key in the name of such devices is the word "optical" - that is, optical. True, the range in which they work is invisible to the human eye, since it is shifted to the infrared (IR) region. All devices of the considered principle of operation are divided into two groups:

passive,
active.

The former are more common due to the ease of installation and configuration. They consist of a receiver, a special lens and an electronic signal processing unit (that's the second part of the name). Among them there is also a division into:

superficial,
linear.

These names come from the type of detection zone - that is, the configuration of the part of the space in which the optoelectronic detector is able to detect an alarm event. This event is the movement of a body of a certain mass with a certain speed. These parameters are determined by its technical characteristics.

The range of detectable velocities usually starts at 0.3 m/s. As for the mass, a lot depends on the distance to the object, the installation height of the detector. In any case, a person is found without problems, pets, in most cases, too. Therefore, there are volumetric infrared detectors with "protection" from pets, weighing, say, up to 10 or 20 kg (prescribed in the passport).

A common disadvantage of all passive optoelectronic sensors is their sensitivity to convection air currents, whether warm air from a heater or a trivial draft. Therefore, when determining the installation locations of these detectors, such moments are taken into account in without fail. Rigidity is also critical. load-bearing structure(absence of vibrations during operation) and protection from extraneous light.

SCOPE OF SECURITY IR DETECTORS

Infrared sensors are used in security alarm systems. as a rule, for organizing the second line of defense, that is, controlling the internal volume of premises by detecting the movement of a potential intruder in them. However, surface and line devices can be used for perimeter security.

Passive surface detectors are used to detect penetration through doors, windows, all kinds of hatches and ceilings. There is only one drawback of this method of their use - they will work when the intruder is already inside the room. That is, there is no talk of early detection of an intrusion attempt.

All passive devices have a relatively short detection distance of 10-20 meters. Volumetric - smaller, linear more. This property determines their installation inside small spaces. If required to be equipped with a burglar alarm large areas, then you can:

install several passive sensors,
use active infrared detectors.

By the way, the latter are intended, as a rule, to protect extended perimeters. open areas, so they have a linear detection zone. In addition, it is technically impossible to implement other types of zones for active devices. To increase the vertical control area, multibeam detectors are used.

Infrared sensors are critical to the optical density of the environment (rain, snow, fog), so this should be taken into account when installing them outdoors.

In conclusion, we can cite several of the most popular lines of models of optoelectronic detectors. domestic manufacturers. These are detectors of the type:

Aster,
Photon,
Icarus.

All of them are issued various designs both by the installation method and by the parameters of the detection zone. For example, Astra 5A is a volumetric detector, 5B is a surface detector, 5B is a linear detector.

Optoelectronic detectors are devices in which optical devices and sensors of various designs are used to detect an alarm event. Further processing of the received signal is carried out electronic circuit. Such devices are widely used in both security and fire alarm systems.

The main reasons for their popularity are:

high efficiency;
the possibility of forming detection zones of various configurations;
relatively low price.

The optical part of these detectors operates in the infrared (IR) range of radiation. Exist various options versions of infrared sensors, differing in the principle of operation, purpose and application features.

Passive.

Used in security alarm systems. Their main advantages are economic availability and a wide range of applications. The principle of operation is based on the analysis of the difference in IR radiation between the sectors formed by special lenses (Fresnel).

The receiver of the infrared stream is a pyroelectric module that generates electrical impulses processed by electronics.

Modern detectors quite often use microprocessor signal processing, which increases their reliability, efficiency and resistance to interference.

Active.

They evaluate changes in the intensity of the IR beam generated by their transmitter. Structurally, the receiving and transmitting parts can be placed in separate blocks installed opposite each other. In this case, the part of the space between them is controlled.

With a monoblock design, a special reflector is used to return the beam to the device. Such detectors are used in security and fire systems.

The operation of such devices is considered in sufficient detail in the article about linear sensors used in fire alarms.

In addition to the "classic" wired devices that use relays to transmit information about their state, there are addressable opto-electronic detectors. By transmitting a signal to the receiving and control device, they add their own code, unique for each product, to the information.

Due to this, it becomes possible to localize an alarm event with an accuracy up to the location of the sensor installation. Their cost, of course, is higher, but in some cases it is worth it.

Another technology is addressable analog. It implies the transmission of digitized data of the scanned parameter, on the basis of which the decision to generate an alarm is made by the control panel. Such detectors are mainly used in fire protection systems.

The last thing worth noting is the signal transmission methods. There are actually two of them:

wired;
radio channel.

SECURITY OPTO-ELECTRONIC DETECTORS

The principle of operation of security optoelectronic devices is described at the beginning of this article. As for detection zones, passive infrared detectors allow you to use all possible options:

bulk;
surface (curtain);
linear (beam).

Active ones work according to the last (ray) principle.

All of them are inherently motion sensors, that is, they detect the movement of an object in a protected area. For surface and linear, it would be more correct to say - the intersection of the detection zone. You can see more about how it works.

FIRE OPTO-ELECTRONIC DETECTORS

Optoelectronic devices used in fire alarm systems and automatic fire extinguishing installations belong to smoke detectors. According to the type of detection zone, they are divided into:

point;
linear.

Point ones incorporate a smoke chamber. It is a kind of labyrinth at the beginning and end of which an emitter and a photodetector are installed. When smoke gets inside, IR radiation is scattered, which is recorded by the electronic circuit of the device.

The scope of such detectors is very wide, they are installed in offices, shops, hotels and other similar facilities. According to the type of information signal formation, they are divided into:

threshold;
targeted;
addressable analog.

According to the method of communication with fire alarm devices, these detectors are wired and wireless (radio channel).

In general, these are quite versatile sensors that allow solving various issues of providing fire safety. It is somewhat inconvenient, and sometimes economically impractical, to use them for installation in rooms of a large area and (or) a large distance from the ceiling.

In this case, linear optoelectronic detectors are used in fire alarm systems. They do not have a gas chamber and control the optical density of the medium by analyzing the parameters of the infrared beam. For these purposes, a receiver and a transmitter are required, that is, such devices are active.

A general limitation on the use of optoelectronic fire detectors is rooms with a high dust content. In addition, such devices may be affected by electromagnetic interference. But this largely depends on the model of the sensor.

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