Sound or acoustic detectors used in systems burglar alarm designed to detect broken glass in windows, shop windows, decorative doors. They have a surface detection zone and use addressable, wired or wireless data transmission methods.
Sometimes security detectors are called sensors. This is not entirely correct, but it is quite acceptable if you do not find fault with the severity of the wording.
Any acoustic detector includes:
- microphone;
- signal processing unit;
- actuator.
The principle of its operation is to convert an acoustic signal (the sound of breaking glass) into an electrical one. Wired sensors are included in the security loop. Radio channels are used in wireless alarm systems. The difference between these versions is in the design of the actuator.
Wired ones generate a notification about their status by switching relay contacts. There are two options here: on or off, respectively, the information content is minimal. However, there are targeted executions. They can also use wires, but the signal is digital.
More information about the status can be conveyed:
- taken;
- removed;
- anxiety;
- malfunction.
As a rule, this is enough to organize reliable security.
Wireless sound detectors use a radio channel in a specially allocated frequency spectrum to transmit data. They are addressable with all the advantages of such data transmission technology.
Wireless versions are powered from a built-in autonomous source (battery, accumulator). Wired ones are connected to the power supply through a separate input, while addressable ones receive voltage via a loop.
TECHNICAL CHARACTERISTICS OF ACOUSTIC DETECTORS
Since we are dealing with superficial principle detection, then one of the main parameters is the area of the controlled surface. As a rule, the passport data indicates its minimum value, below which the reliability of detection of glass breakage is not guaranteed.
The upper limit is determined indirectly based on two values:
- acoustic range;
- viewing angle.
As a rule, their values are 6 meters and 120 o, but there may be exceptions.
The sound of broken glass (spectrum and frequency) depends on its brand, thickness, presence of reinforcement, etc. The device passport must contain information about the types of glass sheets for which a specific detector model is suitable for blocking.
To reduce the level of false alarms, manufacturers implement the principle of analyzing two components of the audio spectrum:
- low-frequency component corresponding to the impact on the canvas;
- high-frequency, accompanying the stage of destruction and shedding of fragments.
On the one hand, this is good, on the other hand, you can cover the window with a film that will prevent glass residues from falling out and muffle the high-frequency component of acoustic vibrations. An alarm signal may not be generated. The effectiveness of security can be increased by using a combined detector, combining sound and surface infrared detectors.
Acoustic security detectors may have additional features sensitivity adjustment, microphone position (two-position versions).
Next are the parameters that determine electrical characteristics and operating modes of the product: voltage and switching current of relay contacts (for wired), operating frequency (for wireless), supply voltage, temperature range, climatic version.
INSTALLATION AND CONNECTION OF GLASS BREAK SENSORS
Most often, sound detectors are used to block windows. The location of their installation should be chosen so that all points of the protected surface are located at a distance not exceeding the rated range. The direction of the acoustic axis of the device must ensure that the glazing is located in the viewing area declared by the manufacturer.
Possible installation locations:
- ceiling;
- walls;
- window slopes.
Each has pros and cons. For example, mounting on the ceiling makes it possible to block several windows with one sensor (if the range allows). In addition, when suspended ceilings"Armstrong" type, it is convenient to hide the cable wires behind them - the design does not suffer. On the other hand, if there are blinds (curtains) installed on the windows, they can reduce the sound of breaking glass so much that the detector will not go off.
This is prevented by installing the device on a slope. But at the same time:
- there may not be enough space for convenient installation and maintenance;
- the sensor may interfere with the free opening of frames;
- part of the surface may be in the “blind spot” outside the viewing angle.
In most cases, the last point is not critical. Concerning wall installation, then this option is similar to the ceiling one. The only problem that arises is with the wiring and connection.
At one time, private security used acoustic detectors in loops alarm system for prompt transmission of a signal about a robbery attack. For example, breaking a jewelry store window. This was called an alarm system that was triggered independently of personnel actions.
Since the system was activated during working hours, alarms occurred in response to telephone calls and the ringing of dropped keys, despite the stated microprocessor processing of the signal. Thus, the acoustic background of the room affects the stability and reliability of the detector.
Choosing a location for installing a wireless sound detector is no different. The only thing is that you need to take into account the presence of interior items, building structures, contributing to the weakening of the signal, and also provide ease of access for replacing batteries.
Protection against sabotage.
There are several ways of sabotage (depriving the detector of the ability to perform its functions):
- changing the electrical part of the loop (more often - installing jumpers);
- sealing the hole under the microphone with soundproof material.
The first option is prevented by concealed routing of the loop, making connections inside the detector body, and connecting the tamper (tamper sensor) of the detector (if available, of course) into a separate, dedicated 24-hour loop. This is a reliable solution, but in practice few people do this - it complicates installation.
In addition, there remains a second method, which can only be combated by limiting unauthorized access to the detector. This automatically solves the first problem. To be honest, there are many ways to sabotage a security alarm. There are also enough ways to combat this, so with proper design and installation of the system, reliability can be brought closer to 100%.
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© 2014-2020 All rights reserved.
The materials on the site are for informational purposes only and cannot be used as guidelines or normative documents.
The main requirements for all systems are to inform people inside buildings and structures as quickly as possible about gas contamination/smoke, and detection of signs of open burning.
Types
By technical device, principles of operation, as well as the time of invention, appearance on the market of equipment, components of security systems, sound detectors fire alarm divided into 3 types:
- Electromechanical. They form low-frequency sound vibrations that are clearly distinguishable from background noise, and therefore immediately attract the attention of others. As a rule, taking into account the characteristics and experience of use, they are installed in large areas/building volumes or on open technological sites, territories industrial facilities, warehouse complexes, motor transport enterprises, parking.
- Electrodynamic. Such devices produce a powerful low-frequency signal with an unpleasant sound up to 110 dB with a wide sound pressure diagram.
- Piezoelectric. Produces sound vibrations using a piezoceramic crystal. Today, these are the most common products in the production of such devices; they are widely used in design, installation, and replacement of equipment for alarm and alarm systems.
According to the design, design of the body/shell, location, and method of installation/assembly of the product, fire sound detectors are:
- Wall, ceiling, incl. mortise, installed in suspended systems.
- Internal/external, as well as universal with a high degree of protection from dust/moisture.
- Normal/explosion-proof version.
- Combined, combined with light fire alarms - various displays, direction indicators.
- Both wired and radio channel devices.
By external dimensions The housings are the most compact/miniature piezoelectric sound PIs.
For example here specifications several popular/common products on the market of fire-fighting equipment from domestic companies:
- Sound fire alarms "Ton-1S-12" and "Ton-1S-24" produced by the IRSET-Center plant from St. Petersburg, differing only in the power supply voltage - 12 and 24 V. Otherwise, all technical characteristics are the same - dimensions, body diameter 105, height 67 mm, sound pressure level not less than 85 dB, signal frequency range 2500–3500 Hz, operating range – from – 40 to + 55℃.
- "Mayak-12/24 ZM/M1" manufactured by the company "Electrical Engineering and Automation" from Omsk with a sound pressure level of 105 dB, dimensions 80x80x55/100x80x30, power supply 12 and 24 V, degree of protection IP56/IP 55, operating temperature range from - 50 up to +55℃.
- "Pipe-2". It is a security and fire sound siren from the Bolid company, the most famous security system equipment on the Russian market. Various modifications of this product are available, operating from a low-current network of 12 or 24 V, with one or two piezo-crystal sound emitters, with an additional light annunciator, and a volume level at a distance of 1 m - 100/105 dB. Made in a metal case in a waterproof design, intended for indoor/outdoor installation at temperatures from – 30 to + 50℃. Dimensions – 66x92x118 mm with a product weight of no more than 0.6 kg.
- “Flute-12” produced by Arsenal Security Group from Omsk is also intended for use as a sound annunciator in alarm systems. Case material – plastic. Power supply – 9–13.8 V. Signal volume level – 105 dB. The carrier frequency range is 200–5000 Hz. Dimensions – 134x134x50 mm, weight only 70 g. Protection against dust/moisture in indoor air – IP Operating temperature range – from – 30 to + 55℃. This group of companies also produces the Grom-12M sound PI with similar technical characteristics.
In total, there are several dozen models of sound, light and sound PIs from various manufacturing companies with similar parameters, but with different protection of products from external environment, with versions ranging from normal to explosion-proof, in metal/plastic housings.
Design and principle of operation
As already mentioned, audible fire detectors are three main types of devices, in the housing of which incentive elements are mounted that create sound vibrations/signals.
They differ in design and operating principle:
- In an electromechanical fire alarm sounder, it is an electromagnet with a movable core, whose oscillatory movements, when an electrical signal is supplied from the APS control and reception equipment to the coil winding, lead to impacts on the bells installed in the product body. The result is a sound wave with a frequency depending on the size/shape of the bell. There is no need to talk about particularly compact dimensions with such a product design.
- The electrodynamic type sound fire detector is equipped with a moving coil with a magnet. This type of device for converting an electrical signal into sound vibrations is used in most speaker systems, incl. sound/voice warning of a fire.
- The sound that a piezoelectric sound detector makes is produced by vibrations metal plate, rigidly connected to a piezoceramic crystal, when an alternating current is applied to it electric current. Such products are compact to the point of miniature, and therefore are in demand for installation in rooms with high requirements for interior design.
These features are taken into account by experts design organizations when choosing the type/type of sound PIs.
Application area
The mandatory use of audible fire detectors when constructing diagrams of any alarm fire alarm installations, the possibility of their use in individual rooms/areas in warning systems/control of evacuation flows of types 3–5 is dictated by the requirements for the design of these security systems.
According to the standards, only sound notification is allowed to be used:
- In kindergartens/nurseries with the number of floors/seats - in one-story/up to 100, in two-story/up to 150 children.
- In the buildings of hotels/hotels, sanatoriums/rest homes - up to three floors/up to 50 residents.
- In cinema halls, concert halls, libraries - up to 100 visitors.
- In museum/exhibition buildings – up to three floors high/up to 500 visitors.
- In one/two-story buildings of trade organizations with an area of up to 3500 sq. m.
- School buildings are 1 or 2 floors high with the number of students in them - up to 350 people.
In many ways, the use of such alarms is due to the fact that their sharp/unpleasant loud sounds - sirens, tinted signals - easily and quickly attract attention even in the premises of educational, administrative, entertainment institutions/institutions, where the level of everyday background noise is high.
In addition, the security and fire sound detector is used as universal device in installations/systems of OPS, SOUE types 1, 2, according to the standards, it is mandatory for installation in the following industrial, warehouse buildings, parking lots for vehicles, depending on the number of storeys of buildings/structures and:
- One-story - from A to D.
- From 2 to 8 floors – V.
- From 2 to 10 floors – G, D.
During installation/installation, sound PIs must:
- Provide pressure level sound signal not less than 75 dBA when located 3 m from the product, but not more than 120 dBA at any point in the protected space/premises. It’s interesting, but manufacturers stubbornly indicate information about sound pressure of their products, tested for some reason at a distance of 1 m.
- Placed at a height of at least 2.3 m from the floor level to the top of the product body, but with a minimum distance of 0.15 m from the ceiling to it.
- The required number of both audio and speech PIs, their correct placement/arrangement should provide the required level of warning signal in premises with permanent workplaces/temporary stay of workers/employees, visitors/customers, clients/patients in them.
When selecting specific products for the scheme/specification of the APS/SOUE project important parameters are:
- Sound pressure level.
- Power supply voltage.
- Current consumption value.
- Climate options.
There are quite a lot of questions, starting from the stage of inspection of objects to be equipped with APS and SOUE installations; therefore, specialists from design institutes/bureaus and enterprises providing installation and maintenance services for such security systems should be involved in creating warning schemes, carrying out acoustic calculations, and installing sound PIs.
Designation
The fire alarm sounder sign is located at the location of the sounder or together with the sign “Button for turning on fire automatics installations (systems”).
Shape: square Background: red Symbol: white
Advantages and disadvantages
The advantages of using sound fire detectors at sites are obvious:
- These are reliable, vibration- and electromagnetic-resistant products.
- They are compatible with all other APS/SOUE equipment - monitoring/control devices, uninterruptible/redundant power supplies with 12–24 V power supply, .
- Their price is low, so even use in each protected room, near emergency exits, slightly increases the total cost of the APS/SOUE system.
There are no obvious shortcomings during their installation, operation, or service. It’s unlikely that loud should be included among them unpleasant sound, the generation of which in the event of a fire is their direct purpose.
Development of microelectronics, use/implementation of inventions in production different types components of fire automatics systems leads to the fact that sound PIs become an integral part of not only light and sound devices, but also multisensory sensors.
The most vulnerable area in the room is the window openings. There is nothing easier for an intruder than to break glass and get inside a building. To protect them, roller shutters are installed, but they are not very difficult to open.
Therefore, surface sound detectors are increasingly used as protection against unauthorized entry. security type. It can be installed on any type of glass and is triggered when it breaks.
What is a sound sensor?
In such a detector, the role of a sensitive element is played by a condenser microphone, inside of which a preamplifier is built. The process of operation of the device is to transmit a signal from a microphone to an amplifier, converting it from electrical, and from it to a microcontroller. The latter checks the supply voltage and generates warning signals.
Devices of this type appeared on the security systems market back in the early 90s, but still remain relevant. Over time, they have become more advanced, the number of false alarms has decreased and the accuracy of recording the destruction of the glass surface has increased.
A surface sound security sensor is triggered by a specific signal, for example, breaking glass. The operating principle of such a device is not very complicated, it is as follows. Looking at the structure of the device, you can see that it contains a microphone. All the main work is done by this part. It converts sound into an electrical signal. Also included in the sensor mechanism are other electronic devices, responsible for dividing the signal into components with their subsequent analysis.
What is an acoustic sensor:
If the sound produced coincides with the standards characteristic of breaking glass, a signal is generated that is sent to the control panel. This principle of operation very often leads to false positives, so it was slightly modified.
Now the resulting signal is divided into low and high frequency components, which are analyzed separately. This made it possible to somewhat reduce the number of false signals, but it has not yet been possible to completely avoid them.
Depending on what glass different types may produce different sounds during the breaking process, sound sensors have several types of markings corresponding to the type of glass in terms of thickness, density and surface type. In addition, most modern sensors have fine tuning sensitivity, which makes their work effective.
Types of sound detectors
The classification of this type of security equipment depends on the operating principle of the devices. They are divided into:
- electro-contact – working to fix the mechanical integrity of the glass
- impact-contact - triggered when vibrations occur that characterize mechanical destruction of the surface
- acoustic – defining sound vibrations that arise during the breaking process
Sensors of the first type are currently practically not used, since the installation of such devices has its own difficulties and is quite labor-intensive. Another disadvantage is the fact that such detectors are too clearly visible to intruders and consist of a strip of foil or wire located around the perimeter of the glass.
Let's look at the shock-contact sensor:
Impact-contact models react to impact by any object. They generate a signal when the inertial properties of the elements are triggered. Installation of such devices is carried out on inner surface glass, which limits their use, especially for large buildings.
Acoustic devices are among the most effective. They successfully combine ease of installation and operation. One such device is installed for several window openings at the same time, which allows reducing the cost of the security system. The detector reacts to the sound of breaking glass, not only picking it up, but also conducting full analysis situations.
Choosing the best brand of sensor – Flute or Harp?
Surface security detectors are produced by manufacturers from both domestic and foreign companies.
Among them, the most popular products are the following companies:
- Argus-Spectrum (St. Petersburg)
- STC Teko (Kazan)
- Pyronix (UK)
- DSC (Canada)
- Crow (Israel)
It is impossible to review the products of each manufacturer in one article, so we will focus on a review of only two models produced by domestic companies - the Arfa and Svirel detectors.
The Arfa brand security surface sound detector is a miniature sensor that is used to detect glass breaking in windows or door leaf. In this case, a signal is generated by opening the relay contacts of the device.
The sensor can be installed on any vertical design, dividing space or window opening. Depending on the location, you can change the sensitivity of the device.
Its main advantage is the ability to detect damage for 6 types of glass: from the most ordinary to reinforced or coated with a special film.
Moreover, having a high detecting ability, the device is capable of detecting even the smallest destruction of glazed fragments.
The Svirel detector belongs to the security and fire equipment. It is most often used to provide a siren-type signal when unauthorized entry into an object is detected. Devices of this brand are available in 4 modifications with one or two piezoelectric emitters for 12 or 24 V.
Watch a video about Crow products:
Application of surface security detectors sound type The pipe is allowed both indoors and outdoors, thanks to the waterproof design of the case. They are capable of ensuring effective collaboration with various control panels that have an output used to supply voltage direct current when the sensor is triggered.
What should you not forget when choosing?
Big variety modern models addressable surface sound security detectors S2000 ST provides for the possibility of purchasing equipment taking into account the acoustics of the controlled object, which allows you to practically avoid false alarms.
However, when choosing, the most important parameters include the following:
- type, thickness and area of the surface to be served
- range of the device
- presence of anti-masking
- power supply type
Taking these indicators into account, you will be able to equip your security system with equipment that will ensure high efficiency her work and, therefore, will help preserve the property. It is very difficult to choose one sensor model and evaluate it as the best, because each of them has its own characteristics. Here everything depends on the parameters of the protected object and the desired result that the user expects.
Acoustic burglar alarm detectors are designed to detect glass breakage. By the nature of the detection zone, they are superficial. Structural scheme acoustic detector contains:
- microphone;
- signal processing board;
- output relay (actuator).
It’s worth noting right away that all this applies to the classic wired version of the detector.
For addressable and wireless sensors, a relay is not used. In the first case, a matching device with the alarm loop is used instead, generating a code corresponding to the state of the sound detector. For wireless execution, a radio transmitting module is added.
However, these differences are not fundamental for understanding the operating principle of the described devices. Below we will discuss how security alarm detectors of this type work.
PRINCIPLE OF OPERATION
The operating algorithm of modern security acoustic detectors is as follows:
- the sound of broken glass is converted into an acoustic signal by a microphone;
- electronic circuit carries out its processing and analysis;
- Based on the results, the actuator generates the required notification.
With the first point, everything is quite obvious; the most interesting thing begins at the stage of processing the acoustic signal. Electronics must take into account the following factors accompanying the sound of breaking glass:
Audio signal level.
First of all, this is necessary in order to cut off possible interference, thereby eliminating false positives. Since the acoustic situation at each specific facility is quite individual, manufacturers provide the ability to adjust the sensitivity of the security sensor.
Spectrum analysis.
Additional and more effective way protection against false positives. The fact is that without this option, an acoustic detector can be triggered by the sound of a car passing by, a telephone ringing, etc. Analysis of various frequency components allows you to more accurately identify the nature of the sound impact.
In this case, there is one parameter that should be taken into account when choosing a detector - the thickness of the glass of the controlled surface. Yes - glass of different thicknesses when broken gives different sound. Moreover, the spectrum of the signal when split, for example, ordinary and tempered glass is also different. Please note that this characteristic must be indicated in the passport and characteristics of the detector.
The presence of a low-frequency component.
Another way to get rid of unnecessary triggers. When glass breaks, there is first a blow, producing a low-frequency sound, and then a characteristic ringing sound. So, security detectors with microprocessor signal processing take this moment into account and monitor the desired sequence of sounds.
This triad allows us to provide high level reliability and quality of protection of glass surfaces. We’ll talk about the differences in the operating principles of different types of sound sensors (wireless and addressable) below.
SECURITY SURFACE SOUND DETECTORS
We have looked at the principles of signal processing by acoustic security sensors, now let's move on to methods of transmitting notifications. Essentially there are two of them:
- wired;
- and wireless.
In the first case, a physical connecting line is required for the detectors to operate as part of the security alarm system. You can connect sensors with a relay output and addressable devices. The former have minimal information content, since the relay has two positions - closed and open.
Thus, we obtain the “normal” state, corresponding to the security mode and, as I would call it, “everything else”. This could include disarming, a malfunction of the device, or an alarm mode. It is impossible to identify the reason for the relay operation on the sensor side. In addition, if there are several surface sensors in the alarm loop, we are also not able to quickly determine which one was triggered.
Free from these disadvantages addressable sound detectors surface type.
The principle of their operation is inherent in the name itself - each device has its own individual address, by which it is identified in the alarm system. All information is transmitted in digital code, so it becomes possible to generate more than two notifications, for example:
- norm;
- malfunction;
- anxiety.
An additional advantage is the ability to use one line for a significant number of detectors.
If you want to get rid of wires for one reason or another, you should use wireless acoustic detectors. By the way, all wireless devices, by definition, are addressable, and you can read about their advantages and disadvantages.
Now let's see what specific models of surface sound sensors can offer us modern market security systems. We will limit ourselves to the most popular models, which today are:
- Astra-s - manufacturer CJSC Scientific and Technical Center "TECO", Kazan;
- Glass-3 - manufactured by JSC "Rielta", St. Petersburg;
- Harp - manufacturer "Argus Spectrum" St. Petersburg.
All of them are wired, generating an alarm signal by opening the relay contacts.
Astra-S.
One of the most popular acoustic surface detectors. With a range of up to 6 meters, it allows you to control Various types glazed surfaces (regular and protected with polymer film, reinforced, multilayer and hardened).
The performance is wired, so to speak, a “classic of the genre”. The price is average compared to other models. It has been produced for quite a long time, so it is well-known among many installers. However, it does not differ in any extraordinary parameters. There are cheaper models from the same manufacturer with similar characteristics, for example: Astra 531AK, Astra-612.
Glass-3.
More expensive than Astra, let's see why. Firstly, the range is 9 meters versus 6. Secondly, it has more advanced declared signal processing algorithms and somewhat wider functionality, which is not always critical.
By the way, this trademark has also been known for quite a long time and has a number of modifications: Steklo-2 (powered by an alarm loop), Steklo-3M.
Harp.
The price is also more expensive than Astra, the main technical characteristics (range, temperature regime, energy consumption) are similar. It has more “sophisticated” functionality (in my opinion, Argus Spectrum generally likes to be clever), which not everyone needs. It has also been on the market for a long time, and is also well-known.
It seems to me that the Astra line of models is still optimal for a home or cottage, since it is more budget-friendly, but, I emphasize, this is my personal opinion, albeit based on sufficient experience.
INSTALLATION, MOUNTING AND CONNECTION
Acoustic detectors are installed on walls, ceilings or window slopes. This placement is possible for all models, you just need to take into account the following points:
- the distance to the farthest point of the controlled structure should not exceed the rated range of the detector;
- there should be no foreign objects such as curtains and blinds between the sensor and the monitored surface;
- access to the detector should be convenient, the indicators should be clearly visible - it still needs to be serviced.
A little advice - if the detector cover is fixed with a latch, then provide for the possibility of subsequent convenient access to the latch. This is not a trifle, since, for example, installing a sensor on the wall with a latch close to the ceiling will cause quite serious problems for yourself or those who will subsequently service the alarm system.
When connecting a wired sensor to the alarm loop, provide a small supply of wires - if you connect them “tightly” then:
- firstly, it will be inconvenient to do this when disconnecting/connecting the sensor;
- secondly, if the wire breaks off during installation or operation, then building it up will take a lot of your time and nerves.
Of course, everything can be done, but at what cost.
What else you should pay attention to when installing wired detectors is their type. When connecting addressable sensors, as well as devices receiving power via the alarm loop, the polarity of the loop must be observed.
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© 2014 - 2020 All rights reserved.
The site materials are for informational purposes only and cannot be used as guidelines or official documents.
