Sensor
Modern security sensors are conditionally divided into three main groups:
Temperature sensors are a special case: they can belong to any of these three groups.
Note that there are many combined models that combine several types of sensors at once. And here is a detailed description of each individual variety:
- Intersection sensor (barrier). Sensors reacting to the crossing of the guarded perimeter. Such a sensor generates a beam (or several beams) in the infrared range, and when such a beam is crossed by a foreign object, the device gives a signal. Most often, the IR barrier consists of a separately made receiver and transmitter, however, there are also one-sided devices in which the emitter itself “monitors” the reflection of the beam from a certain object. Recall that IR rays are invisible to the naked eye; this makes it possible to effectively disguise such a system. And the range of modern IR barriers can reach several hundred meters.
- Motion Sensor. Sensors that respond to moving objects in the field of view. They can use different principles of operation: infrared, microwave, etc. Motion sensors in the original sense of the term are used mainly as security; in such models, the functions of a break, vibration and / or temperature sensor may be additionally provided. However, there is another variety - household models designed for use as lighting sensors (see below). They are designed to switch the 230 V voltage intended for lighting fixtures (rather than the 12/24 V used in alarm systems), and most often use the same voltage for their own power supply; and other types of detection (except for movement) are not provided in such models. As for the types of work, infrared ones are based on the change in the thermal radiation of objects and can give false alarms due to unforeseen heat flows, and also depend on weather conditions. Combined, which, in addition to the infrared sensor, are equipped with a microwave (microwave), reacts not only to thermal changes. Accordingly, they are less prone to false positives, but much more expensive.
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Infrared (PIR) motion sensor.... The principle of the PIR infrared sensor (from the English passive infrared sensor) is based on fixing changes in thermal radiation from surrounding objects. Such sensors accurately register movement, but are not immune from false alarms due to unforeseen heat flows and depend on weather conditions. There are models that combine several PIR sensors, so they can analyze more changes and more accurately register movement.
— Microwave (SHF) motion sensor. These sensors operate in the microwave radio range similar to a radar: the device periodically emits a pulse and, by analyzing the reflected signal, determines the presence of foreign objects in the controlled space. Such devices are somewhat more complicated and more expensive than infrared ones, but their capabilities are noticeably wider. For example, an IR sensor usually has a limited field of view, while a microwave device is able to "see" the entire 360° around. The "radar" coverage area is not limited to line of sight, it can detect foreign objects behind small obstacles - like window glass or partitions between workstations in an office. In addition, the microwave sensor is equally effective over the entire temperature range. Among the disadvantages, in addition to cost, it can be noted that it is undesirable to use them when people are constantly in the area of microwave action. However, most alarms still turn on only when there are no people in the room.
- Combined (PIR + microwave) motion sensor. Such models consist of two types of sensors, infrared (PIR) and microwave (microwave). Combined solutions combine two dissimilar technologies, which minimizes the number of false positives. In addition to thermal analysis, these devices emit electromagnetic waves at a high frequency, typically 5.8 GHz (may differ depending on the manufacturer). These waves are bounced off the surrounding objects, so that the sensor can register even slight changes.
- Break sensor. Security sensors that react to glass breaking. Nowadays, such sensors are most often made contactless and do not require placement on the glass itself, although there are exceptions. And the most popular principle of their work is acoustic: with the help of a microphone, the sensor “listens” to the environment and reacts to the sound of breaking glass (this sound is quite unique, it is easy to separate it from extraneous noise). There are other principles of operation, for example, infrared (reaction to a sharp change in the visible "picture") or vibration (tracking shocks and vibrations using a contact sensor). Some models also have the functionality of a motion sensor, and sometimes a full-fledged vibration sensor.
- Opening sensor. Security sensors that respond to the opening of windows, doors, hatches, etc. As a rule, the sensor itself is placed in a door or window opening, and a special mark is placed on the door / window. When closed, this label is in close proximity to the main device, and when opened, it moves away and the sensor is triggered. Such sensors may also have vibration and/or temperature detection.
- Vibration sensor. Security sensors that respond to various shocks and vibrations. They can be used for different purposes. For example, such a sensor can warn of an attempt to open a door or window, climb over a fence, crack a safe or an entire wall of a building; It can be mounted on a cabinet door or desk drawer as an opening alarm. And some of these devices are so sensitive that they can even be placed near individual valuable items - so that the sensor reacts to any attempt to move such an object from its place. On sale there are both specialized vibration sensors and models with combined functionality that also respond to movement, breaking, opening and / or temperature.
- Smoke detector. Fire-fighting sensors that react to the appearance of smoke in the air. This is one of the simplest and most reliable methods for detecting a fire: smoke during fires is almost guaranteed, and even with a low intensity of the flame, smoke is often quite significant. For additional reliability, such detectors can be combined with gas and/or temperature sensors.
- Gas sensor. Fire detectors that react to the presence of a certain gas in the air. The specific format of operation of such devices may be different. So, some models react to carbon monoxide (CO) - not only is it a product of combustion and a sign of fire, but it is also dangerous in itself, so such a sensor also provides protection against carbon monoxide poisoning. A number of devices are triggered when a significant amount of domestic gas appears in the air (for example, from an open burner or a damaged pipeline), methane, propane-butane, etc. - in such cases, timely notification avoids an explosion. Finally, sensors that are able to detect sleeping gases are marked in a separate line. Note that gas sensors may also have smoke and/or temperature response functions.
— Leak sensor (flooding). Household sensors that react to the appearance of moisture on the floor or other surfaces. Such a sensor is installed right in the place of possible flooding, and a pair (or several pairs) of special contacts are used for detection: even a small amount of water between the terminals closes them and leads to operation. Contacts can be placed both on the sensor body itself and on a remote unit connected to it with a wire. Some of these devices also have a temperature sensor function.
- Temperature sensor. By itself, temperature detection is very versatile, it is used in all major formats of sensors - security, fire, domestic. At the same time, there are very few temperature sensors in their pure form - these are separate fire models that respond to a significant increase in temperature. In the security format, this type of detection is most often combined with motion or opening detection; Specifically, a thermal sensor in security systems can provide, for example, tracking heat from living objects or responding to a change in temperature in a room when a door / window is opened. As for domestic use, here we are talking about monitoring and controlling the microclimate in the room; To this end, sensors of this type are often supplemented with humidity sensors.
- Humidity sensor. Household sensors that monitor indoor air humidity. Humidity is one of the key characteristics of the microclimate, maintaining a certain level is necessary both for the normal well-being of people and for more specific tasks - ensuring optimal conditions in a warehouse, workshop, laboratory, etc. Note that pure humidity sensors are found rare, usually this function is combined with temperature detection.
— Lighting. Sensors designed to automatically turn on and off lighting. Almost all such models are a special kind of motion sensors described above. And the main difference from traditional (security) motion sensors is that this type of sensors is used to switch the voltage of 230 V (and not 12/24 V); the same voltage is often used for its own power supply, although there are also models with batteries / accumulators. In addition, most of these devices have brightness control (see "Functions and Capabilities"). The light sensor can also be used for security purposes - to illuminate a moving object that has entered the protected area. However, most often such sensors provide convenience in purely everyday situations - for example, to turn on the light in a dark entrance when a person enters it.Communication protocol
Communication protocol (standard) used by the wireless format sensor (see “Connection”).
This parameter directly affects compatibility - the equipment with which the sensor is used must support the same protocol, otherwise normal operation will not be possible. As for specific options, modern sensors can use both common standards
Wi-Fi and
Bluetooth, as well as specialized protocols - most often
Z-Wave,
Zigbee,
Jeweler or
Fibra. Sensors can also operate at
their own frequency. Here is a more detailed description of each of these standards:
- Wi-Fi. A technology used primarily for building wireless computer networks, and more recently also for direct communication between individual devices. For communications, the 2.4 GHz or 5 GHz band is most often used. In the case of wireless sensors, one of the advantages of Wi-Fi is that it is a widely accepted standard; thanks to this, many sensors with this type of communication can work without special equipment - they are able to connect to ordinary wireless routers or even individual devices such as laptops and tablets (some models even allow sending notifications via the Internet, through the same router). However, this versatility also has a downside: Wi-Fi does not have ad
...ditional optimization for working with wireless sensors. As a result, such communication is inferior to specialized protocols in terms of overall reliability, special functionality and energy efficiency. So this type of communication is typical mainly for devices designed for simple conditions of use - such as climate temperature/humidity sensors for smart home systems.
— Bluetooth. Another commonly used wireless communication standard. Operates in the 2.4 GHz band; Unlike Wi-Fi, it is used only for direct communication between devices. It is also poorly suited for professional use (in particular, the response delay can reach 2–3 seconds), and therefore is found mainly in household sensors designed for communication to smartphones/tablets or smart home systems. The most commonly used protocol for communication is Bluetooth LE, supported by Bluetooth modules version 4.0 and higher: it is specially designed for miniature devices with small built-in batteries, allows data transfer with very low energy costs and at the same time provides a range of up to 100 m.
- Z-Wave. Communication protocol developed specifically for automation and remote control systems. Provides for the transmission of the simplest and shortest control commands with minimal delays; Communication uses a range of up to 1 GHz, making such communication virtually immune to interference from Wi-Fi and Bluetooth devices located nearby. Another interesting feature of Z-Wave is the use of a MESH type topology. The signal from a sensor in such a network can be transmitted to the control device either directly or through any number of intermediate nodes, and the optimal route is determined taking into account the current situation: for example, if one of the nodes on the shortest signal path fails, the information will go “to bypass", through other repeaters within range. However, it is worth noting that MESH relay significantly increases energy consumption, so Z-Wave nodes powered by batteries/accumulators do not perform it.
- Zigbee. Another communication protocol created for automation systems (including smart home), alarms, industrial control, etc. Optimized for secure data transfer at low speeds and with minimal power consumption acceptable for miniature battery-powered devices. Just like the Z-Wave described above, it uses a MESH network topology, with the ability to transmit a signal through several nodes and automatically select the optimal route taking into account the current situation in the network. It is distinguished by good protection and noise immunity, as well as a high response speed (recovery from sleep mode takes about 15 milliseconds), due to which it is quite widely used in modern wireless sensors.
— Jeweler. Ajax Systems' own development, a communication protocol created specifically for protection systems - this is its fundamental difference from the standards described above. The creators declared such advantages as long range (up to 2000 m), high response speed (0.15 ms), low power consumption (up to 7 years of continuous operation in some sensor models), support for several frequencies (with automatic switching when the level of interference or jamming attempt), an advanced system of protection against failures and interference (with high-quality encryption, precise detection of the type of attack and the sensor being hacked, as well as notification of jamming), as well as the ability to operate up to 150 devices on one hub. Among the obvious disadvantages, one can note only its limited use: Jeweler is supported only by devices from Ajax Systems (at least for now). However, special integration modules are produced that allow connecting such sensors to wired and wireless control panels from other manufacturers.
— Fibra. The Fibra wired communication protocol was created by Ajax System specifically for protection systems. The technology inherits the wireless capabilities of the related Jeweler protocol (see above), but all devices are connected using a traditional four-wire cable. One Fibra line up to 2000 m long can connect one sensor or several dozen (together with sirens and keyboards in any combination). The digital architecture when using the Fibra communication protocol is built in the proprietary Ajax PRO application. The transmitted data is protected using floating key encryption, and Fibra communication is organized according to the TDMA principle: each device is allocated a short period of time to exchange data with the hub. The rest of the time, communication modules remain inactive, which significantly reduces power consumption and helps avoid conflicts even when several sensors are triggered simultaneously. Fibra is supported in hardware only by devices from Ajax Systems, however, there are special integration modules that allow you to connect such sensors to wired control panels from other manufacturers.
— Natural frequency. In the context of protection sensors, this parameter refers to the natural frequency at which wireless data exchange is ensured between parts of the protection system. Its specific value is determined by the device manufacturer, but the most common options are 433 - 434 MHz and 868 MHz. Using a natural frequency improves the reliability and protection of the protection system because it reduces the likelihood of interference from other wireless devices operating at similar frequencies. When choosing based on this parameter, it is important to consider equipment compatibility, standards and licensing requirements (in order to avoid potential violations of the law).Features
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Sensitivity adjustment. The ability to change the threshold of the sensor, adjusting it to the specifics of the situation. Such adjustment is mainly used to prevent false positives: for example, so that the outdoor light sensor does not turn on the light, reacting to tree branches swaying in the wind. There are other nuances associated with adjusting the sensitivity; more details about them can be found in special sources.
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Adjustment of illumination. A function mainly used in light sensors. Usually, such devices are equipped with photocells that evaluate the level of ambient light; if it is too light around and there is no need to turn on the lighting, the sensor simply will not respond to “external stimuli”. And adjusting the illumination allows you to adjust the response threshold of the photocell — that is, the level of illumination below which the sensor begins to work for its main purpose.
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Adjustment of the response time. Ability to change the timer on the light sensor. Usually, such sensors, having ceased to detect movement in the field of view, do not turn off the light immediately, but with some delay — this format of operation is considered optimal for a number of reasons. And the adjustment of the response time allows you to set the shutdown time at the request of the user (within certain limits, of course); this can be useful for adjus
...ting the sensor to the particular situation. For example, when installing a lamp over the porch of a private house, the front door to this house may be in the dead zone of the sensor; setting the timer allows you to select the shutdown time so that the owner can easily open this door before the light goes out, and the lamp does not waste extra energy.
— Immunity to animals. A function found mainly in motion sensors, including separate models for lighting. The general idea is already clear from the name: this feature allows you to avoid triggering the sensor on cats, dogs and other animals. Such immunity can be useful not only in the presence of domestic “living creatures”, but also in other situations: for example, if neighboring cats can enter the yard served by the sensor. Note that the threshold for this function can be either fixed (for example, “from 20 kg”) or configurable; this point should be clarified separately. And in IR barriers with this function, a different principle is usually used — determining the height of an object. To do this, the device generates two (or more) parallel beams at different heights, and the short-term shading of the lower beam, which is typical for small animals, is not perceived as a trigger.
— Alarm signal. This feature means that the sensor is capable of sounding its own alarm, usually by means of a built-in siren. Such a signal can be very useful in some situations. For example, a siren from a security motion or breakage sensor can attract the attention of witnesses or even the police, significantly complicating the task of an attacker; and the sound from a smoke or gas sensor alerts all people nearby, allowing you to take action to counter an emergency as quickly as possible. Another useful feature of this function is that many sensors with a siren are able to at least partially perform their task even if communication with the control panel is completely lost.
— Protection against opening/separation. Additional protection against attempts to disable the sensor or interfere with its operation: when such attempts are detected, the sensor gives an alarm. Note that the specific features of such protection may be different, depending on the type and specific model of the sensor. Some devices react to a violation of the integrity of the case, others — to the loss of contact with the supporting surface, others — to characteristic shocks, shocks or vibrations that occur when trying to open or tear off the sensor, etc. Such nuances should be clarified separately. However, anyway, this type of protection provides additional security; it does not give an absolute guarantee against interference in the alarm system, however, it greatly complicates such a task.
— Communication jamming notification. A function found in wireless sensors (see "Connection"). When it detects attempts to jam the wireless connection, such a sensor sends a warning to the control panel, and if the connection is completely lost due to jamming, it turns on its own alarm. This makes it much more difficult to interfere with the wireless alarm system.Response time
The response time of the sensor is, relatively speaking, the “speed of reaction” to the monitored event. Indicated by the time that elapses between the event being recorded and sending a signal to the control panel and/or turning on its own siren.
Theoretically, the shorter the response time of the sensor, the higher the overall reliability of the system, the faster it is able to respond to an event. At the same time, it is worth noting that in most models this time is measured in hundredths of a second — on average, from 0.03 to 0.15 s. Such a difference is fundamental only in very specific situations, when the count really goes to fractions of a second — for example, if a sensor is used to stop an industrial mechanism when a person appears in a dangerous area. In simpler cases, this parameter can be ignored.
Threshold
The ambient temperature at which the temperature sensor is triggered. This parameter is relevant primarily for fire-fighting sensors (see "Sensor"); household and security temperature sensors operate in a slightly different format — they constantly record the temperature, and do not work when a predetermined level is exceeded.
Most often, the response threshold is in the range of 54 ... 59 °C — for most rooms this is clearly above the norm and at the same time this temperature is relatively low, which makes it possible to detect a fire at the earliest stages. At the same time, for some conditions — for example, industrial workshops with equipment that generates a lot of heat — higher values \u200b\u200bmay be required (so that the sensor does not respond to high, but acceptable temperatures). Thus, some fire temperature sensors have the ability to adjust this parameter — namely, an increase in the response temperature. For such models, this paragraph indicates the minimum value of the response threshold, and the adjustment range is specified in the notes.
Communication range
The communication range provided by the wireless sensor (see “Connection”) is the maximum distance to a neighboring device at which the sensor is able to maintain uninterrupted communication.
Note that some communication technologies allow operation through repeaters (for more details, see "Communication Protocol"); in such cases, the actual connection range may be noticeably greater than the sensor's own communication range. However, anyway, note that this parameter is usually given for perfect conditions — within the line of sight, without obstacles in the signal path and interference in the used range. In fact, the range of the sensor may be noticeably lower — especially when working through walls; therefore, it is worth choosing according to this indicator with a certain margin. At the same time, the rule “the more the better” is quite valid here: a long range contributes to the overall reliability and stability of the connection.
Working hours
Operating time of the self-powered sensor on one set of batteries or battery charge (see "Power"). Note that this indicator is quite approximate — it is usually indicated either for an perfect or for a certain “average” mode of operation. The real battery life also depends on a number of practical nuances: the frequency of operations, the communication range, the level of interference, etc., up to the air temperature. So in fact, the operating time may differ from the claimed one, and in the other direction. Nevertheless, according to this characteristic, it is quite possible to both evaluate the overall battery life of the sensor and compare different models with each other: the difference in the indicated operating time usually fully corresponds to the difference in real battery life.
Note that modern sensors have very low power consumption, so their operating time is calculated in months.
Operating temperature
Ambient temperature range in which the sensor is guaranteed to remain operational.
All modern sensors are able to transfer the temperatures typical for residential and office premises without consequences. Therefore, it makes sense to pay attention to this parameter mainly in those cases when the sensor is planned to be used in more unfavorable conditions — for example, on the street, in an unheated room, in a “hot” industrial workshop, etc. At the same time, we emphasize that even for the most "Heat-resistant" models are undesirable exposure to direct sunlight — they can heat the case to temperatures that are much higher than permissible.
Maximum humidity
The highest relative air humidity at which the sensor can be used.
Many models can easily tolerate short-term (up to several hours) stay in a more humid atmosphere; however, for a complete guarantee, it is still better not to exceed the permissible humidity. As for specific numbers, in residential/office spaces (and similar environments) the relative humidity rarely exceeds 70%. But for outdoor use and rooms with high humidity (swimming pools, laundries, etc.), it is advisable to use sensors designed for a humidity of at least 90%.
