Optoelectronic detectors. Security volumetric optical-electronic detector - principle of operation Types and scope

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 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 falls on 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 that 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

long corridors

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. Usage modern technologies The manufacture of lenses makes it possible to ensure an 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 pyrodetector, 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. 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 in their optical characteristics almost indistinguishable from mirror optics.

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 choose the desired shape of the sensitivity zone and makes it possible to adapt the sensor to various configurations of the protected room.

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 what caused it - human body or, for example, space heating, 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 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 alarms, 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 at the same time. At the same time, the geometry of the location of 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 pyroelements, 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 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 short 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, 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 the 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.

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 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, 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 volumetric 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-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. 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:

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 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 Incorrect or incorrect operation of passive optical-electronic IR detectors is caused 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 beams sunlight, as well as the headlights of passing vehicles.
Do not direct the detection zone of the detector at heating elements heating and air conditioning systems, on curtains and curtains that 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 security alarm system.

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

Every mother of a baby knows how difficult it is sometimes for him to measure the temperature. Not only do you need to keep the child, but also for at least 5-8 minutes. Infrared thermometer in such a situation will be an indispensable tool. This is a non-contact thermometer that fixes the temperature using a laser beam on any part of the body. It is convenient to use, just direct the beam or touch any part of the body to get exact value within 2-8 seconds.

For the work of the majority infrared thermometers just insert the batteries. More expensive models have the ability to charge from the network. For ease of choice, we have compiled a rating of the best models based on user reviews and expert recommendations.

Name	price, rub.	Briefly about the main
		The fastest temperature measurement in the frontal, temporal and ear zones - just 2 seconds.
		The most budget in the line of contactless measuring instruments.
		Can be calibrated to mercury thermometer.
		The most accurate temperature measurement.
		Convenient application robust design, and interference protection.
		Takes measurements from a distance of 15 cm, even in complete darkness.
		Multifunctional thermometer - for body, air, food.
		Choice of Celsius or Fahrenheit temperature measurement system.
		The results of the last 32 measurements remain in memory.

Varieties of infrared thermometers

The main difference between all non-contact thermometers is the method of measurement. So, non-contact, ear and forehead ICTs are on sale that measure the temperature in the corresponding zone. This is due to the fact that a certain model is calibrated for a specific zone (by the way, the amount of heat in each zone is different).

ear

The principle of operation is also based on infrared radiation, but this is still a contact device - it is tedious to insert a thermometer into the ear and hold it there for 3-4 seconds. Among the entire arsenal of measuring instruments, this one is the most dangerous, as it can injure the baby's eardrum.

Frontal

Depending on the length of the beam, it is possible to take measurements from a distance of 5-15 cm without touching the body. The functionality of the meter is not limited to this - it can be used to measure the air temperature in the house, food for the child, etc.

Contactless

The most convenient and safe to use. No need to “aim” anywhere to hit exactly on the forehead and even more so to put it in the ear. Pointed at the body and got the value on the display. If used only to measure human body temperature, calibration can be done once and for all. If you have to do other measurements - calibrate each time.

Direct the pyrometer to the forehead or ear for measurement. Other parts of the body, even healthy person may have a temperature significantly different from the usual 36.6 ° C.

The IR thermometer is a device designed for remote temperature measurement - fast, simple and absolutely safe. Below are the top 3 ratings of infrared thermometers for kids.

B.Well WF-1000

The temperature measurement speed is only 2 seconds. The streamlined shape and special sensor allow you to measure the temperature in the ear or on the forehead.

It is very easy to transfer the pyrometer from one mode to another: if a special nozzle is put on the sensor, the thermometer is automatically set to measure in the frontal region, if the nozzle is removed, the bi-well thermometer is ready to measure the temperature in the auricle.

measurement speed;
functional;
screen tips.

not calibrated;
accurately measures only at certain points.

The second model in the line - B.Well WF-2000, is designed only for forehead measurement, it is also convenient to use. Power supply type CR2032.

Appearance - the form of a pistol. The handle has three-finger grooves for a more comfortable grip, and the button to start measurements is made in the form of a trigger. Powered by two AA batteries.

There are two measurement modes: medical is designated as Body (that is, “body”), the accuracy in it is increased, but the measurement range lies between 35 and 43 ° C, lower or higher temperatures are simply not displayed, only the letters Lo (Low) are displayed on the screen , low) or Hi (High, high).

To attract attention in case of elevated temperature, the color of the screen backlight also changes: up to 37.5 ° C it is green (there is no particular cause for concern), between 37.5 and 37.9 it is already orange (dangerous, but not very), and above - red, and beeps five times (serious danger!).

In the second mode - Surface (surface), the range is wider: from 0 to 100 ° C (Hi or Lo will also be displayed above and below), but the error is larger. There is no color differentiation - the backlight is always green.

backlight;
design in the form of a pistol;
auto shutdown.

error, especially noticeable when the batteries are discharged.

Another pistol-shaped model, which is very convenient for non-contact measurements. It has two measurement modes: body temperature and object surface temperature. Inner memory on the last 32 measurements allows you to track the dynamics of temperature changes. The voice announcement function reproduces the measurement results in speech form.

The body temperature measurement range is 32°С-42.5°C, with an increase, the backlight of the LCD screen changes (it is convenient to use even in complete darkness). Measurement range of surrounding objects: from 0°C to +60°C - in this case, the backlight remains invariably blue.

Pros of Sensitek:

minimum error;
light weight - only 15 gr.

although it is indicated that it is designed for 10,000 measurements, after 6 months the batteries need to be changed.

In the same category, it is worth mentioning the IR Thermometer non contact pyrometer - it is the most inexpensive in the line, it will cost only 550 rubles. It is also convenient to use, but it “sins” with incorrect measurements. It is advisable at the very beginning to determine the error using a mercury thermometer and try to change the batteries more often.

The principle of operation of all pyrometers is the same. Only functions and design change. Almost all devices measure not only body temperature (Body, medical), but also the surface of objects. Calibration, depending on the model, is carried out manually or automatically.

Medisana FTN

German pyrometer, one of the best in its class. It is used for forehead, rectal, axillary measurements. Readings are ready in 2 seconds from a distance of up to 15 cm, so no hygienic caps are required. It gives very accurate data (when compared with a mercury thermometer, the error was 0.02 ° C), which, in general, is rare for contactless devices.

The form is convenient, the LCD screen makes it possible to use the pyrometer even in complete darkness. It is convenient to measure the temperature of indoor air, baby bath water, etc.

Body measurement range up to 43.5°C, surface - up to 100°C. The memory stores data on the last 30 readings, which is convenient for health dynamics. Alarm by changing the color of the display from green to bright red at > 37.5°C. Stored in a handy case. Weighs 48 g, powered by 2 AAA batteries, LR03 1.5 V.

convenience;
measurement accuracy.

price.

There are two measurement modes: medical is designated as Body temp (that is, “body”), the accuracy in it is increased, but the measurement range lies between 32 and 42.9 ° C, lower or higher temperatures are simply not displayed. To measure the pyrometer, direct the pyrometer to the forehead or ear. Theoretically, it is possible to measure in the armpits, but the indications will not change from this.

The second mode ms 302 Object temp - to obtain data about the environment. In this case, the range is from 0°C to 118°C.

There is a choice of temperature measurement system in Celsius or Fahrenheit.

Stores information about 64 recent changes in body temp mode. The error is minimal. But it increases as the battery drains.

high measurement accuracy;
the ability to work in Fahrenheit.

DT-8836

It is made in a convenient form of a pistol, it receives information from a distance of 15 cm. The LCD displays data - the backlight is blue in the "healthy" range - up to 37.5 °, above - it lights up in red. The backlight is dim, the numbers are large, which makes it possible to use in the dark. For convenience, you can switch measurements from Celsius to Fahrenheit and vice versa.

The measurement time is 2 sec., after 8 sec. Inactivity, the device turns off. Range for the body: +32°-42.5°С, for objects and air - from +10°С to 99°С. Recommended measuring distance: from 5 to 15 cm. Power supply: 9V, 6F22 (Krona type). Weight 172 grams.

measurement accuracy;
low price;
convenient form;
flashlight.

you can't turn off the sound.

Pyrometers is simple and convenient to use home appliance, designed to measure body temperature in the range from 35 to 43 ° C and surfaces various items within a noticeably wider range, from 0 to 100°C.

AND DT-635

Designed to instantly measure the temperature of a person's body in the ear or on the forehead and the environment. It also combines the functions of a clock and a room thermometer. Can be used on the human body in the ear and forehead, any object within the temperature range of the device (up to 50°C), alcohol before serving, indoor air, food storage in the refrigerator, etc.

Only the last reading is stored in the device memory. Convenient case-stand and case for storage and transportation included. Serves sound signals at the end of the measurement and at temperatures above 38°C. Power supply: 1 lithium battery type CR2032.

clock and room thermometer functions;
2 measuring methods.

an error that increases as the batteries are discharged.

A new model with similar specifications, but with a different body shape, powered by AAA batteries, not AA like the IT-1, so it's slightly lighter. Designed to measure the temperature of the body, surfaces and air. This device has a wide measurement range and high accuracy, easy to use. Does not require skin contact, so there is no need to change hygienic caps.

Displays the saved data of the last measurement. The high-speed sensor ensures fast and accurate measurement. Information is displayed on the liquid crystal display Automatically turns off after 8 seconds of inactivity. Power type: 2 x LR03.

quality assembly;
ease of use;
minimal deviations;
very convenient and practical.

Chinese pyrometer for remote measurement of body temperature, air, objects. Information is displayed on a large LCD display with backlight. The memory stores the results of the last 32 measurements. Sound signalization of the end of the measurement. Laica sa5900 Automatically turns off after 10 seconds of inactivity.

Power is supplied by 2 AA 1.5V batteries. It is recommended to change the batteries after 6 months of use. Remove the batteries for extended periods of inactivity.

convenient form;
fast information.

after a long period of inactivity measurement errors.

All manufacturers are trying to make devices as convenient and accurate as possible, although, admittedly, not everyone succeeds.

When operating, follow certain rules:

Monitor the condition of the batteries - as soon as information about the discharge appears, you should replace it.
The IR sensor lens must always be kept clean.
A wet forehead gives large errors.
Measurement in the ear in 9 cases out of 10 will be inaccurate - it is difficult to direct the beam into the opening of the ear canal. It is best to measure the temperature on the forehead.
Take 2-3 measurements at once with an interval of a minute and a half.
In children, heat exchange is more intense than in adults, so it is best to use contact thermometers.

VIDEO: How to choose a non-contact thermometer - Komarovsky's advice

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 large quantity 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.

By configuration controlled zone 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. It is located on a 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 installed on hard surfaces without strong vibration. In permanent structures, the sensor is mounted on a wall or ceiling. In rooms made of light metal structures, they are mounted on the load-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 checking window openings, joint application with 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 has been operating on the Russian market 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 detector volumetric optical-electronic street "Piron-8"

These instruments are devices that use optical instruments and sensors to detect an unauthorized event. The final analysis of the signal takes place in the electronic circuit. Optoelectronic detectors are often used in security and fire alarm systems.

The main reasons why they are so popular are:

high efficiency;
different areas of location;
small cost.

The optical part of these devices operates in the infrared region of radiation. There are many ways to install infrared devices.

Passive

Applied in security systems. The main advantages are low price and a wide range of applications. Passive devices analyze changes in IR radiation.

Active

The principle of operation consists of estimating the difference in the intensity of the IR beam, which is produced by the emitter. The emitter and receiver can be in different blocks and in one. In the first case, only that part of the territory that is between them is protected.

If both devices are in the same module, then a special reflector is used.

There are also addressable optoelectronic devices that transmit the control panel signal and indicate a unique code for any device. Thanks to this, you can accurately find out the place where the sensor worked. However, the price of such devices is higher, but if you want a reliable system, then this option is the most suitable.

There is another type of detectors - addressable analog. This option transmits the digitized information to the control panel, where it is decided whether to apply the alarm signal.

There are several options for transferring data: wired and radio channel.

Security detectors

The location zones of these devices can be volumetric, surface, and linear. Any of these types is a motion sensor, it turns out that it detects movement in a protected area.

The use of surface devices is constrained by the blocking of structures indoors. Linear are usually used for outdoor areas.

Optoelectronic devices are negative to the presence of air currents and to extraneous light sources.

Active linear devices are smaller than others, dependent on the influence of external factors. But they are difficult to set up, especially when using devices with a large radius of action.

Fire detectors

This type of device is divided into turned and linear detectors. In the first case, the device has a smoke block and is a labyrinth with a transmitter and receiver at the ends. If smoke penetrates inside, then the IR radiation is scattered and this is noted by the receiver.

Such devices are used in many facilities, mainly service, that is, offices, shops, and so on. According to the type of data signal sending, optoelectronic detectors are divided into threshold, and addressable analog. And according to the method of connection with the devices of the fire system, they are divided into wired and radio channel.

Such devices are quite versatile and help in ensuring fire safety. But for large rooms, this type of detector should not be used better.

In such cases, linear optoelectronic devices are better suited. They control the air density by processing the IR parameters. Line detectors include a transmitter and a receiver and are active devices.

Popular Models

Arton-IPD 3.1M

Optical spot fire smoke detector SPD-3.1 (IPD-3.1M). The device is designed to detect fires in enclosed spaces of buildings and structures, accompanied by the appearance of smoke. When triggered, it transmits a signal to the control panel.

Designed for continuous round-the-clock operation on a direct current or alternating two-wire loop fire alarm. The rated supply voltage of the loop is 12 or 24 V. To operate the detectors with the control panel according to the four-wire scheme for connecting the detectors, the MUSH-2 loop matching module is used.

Astra-7B (IO409-15B)

The announcer is security volumetric optical-electronic. Designed to detect penetration into the protected area and generate an alarm notification by opening the output contacts of the alarm relay.

It is installed on the ceiling, the detection zone is circular and volumetric, the maximum installation height is up to 5 meters. Microprocessor-based signal analysis, temperature compensation, resistance to external illumination, case opening control, optoelectronic relay. It can work at temperatures from -30 to +50 C and humidity up to 95%.

AMBER

Designed to detect intrusion into the protected area of a closed room. Generates an alarm by opening the relay contacts. Widely used in security alarm systems.

It detects movement in a zone with a range of 12m and a width of 20m, a viewing angle of 90 degrees. The recommended installation height is 2.4m. Supply voltage 12V, operates at temperatures from -30 to +55C. Detects movement at speeds of 0.3..3 m/s.

Useful video

The video explains in detail the device and the principle of operation of devices using the example of a smoke autonomous detector DIP-34AVT from the company.

Conclusion

Optoelectronic emitters are a common and effective component for fire and security alarm systems. Their main advantages include relatively low price, versatility, and reliability.

The main limitation on the use of such devices is problems when working in an environment with a high content of dust, that is, in industrial premises. Optoelectronic detectors are also subject to electromagnetic interference.

The most common motion detectors used in fire and security alarms are optoelectronic 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 optoelectronic 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 one loop. 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. Different models may have a different number of beam children, their sizes and configurations. 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, strong building construction eliminating the possibility of excessive vibrations;
The receiver of two-position devices must be placed so as to exclude the possibility of the influence of intense artificial and natural light to 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 because they are cheaper devices, and due to the wide choice (Fresnel lens systems), 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 alarm systems 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 of 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 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 of 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.