How to reduce the false alarm rate and false alarm rate of anti-theft alarm system?

False alarms often bring unnecessary trouble to the person in charge of safety and users, affecting their normal work and life. Especially for the police / security personnel, when the siren sounds, generally a large number of police forces will be mobilized to attack, resulting in a waste of a lot of time and human and material resources. The bigger price is that, over time, the false positives have made them lose their sense of urgency for the danger and eventually cause a disaster. The consequences of underreporting are even more unimaginable. The so-called military training is used for a long time. If the invasion actually occurs, the alarm will fail. Not only does it cause personal injury or property damage, the user's confidence in the system will be greatly reduced.

The causes of false alarms are very complicated, such as damage to components and poor production processes; it is related to the selected equipment, installation method, angle, and location. For example, choose a vibration detector or bat near the source (airside, railway) False alarms of ultrasonic detectors are often used in places that are frequent; affected by the environment, such as air flow, pet actions, etc .; there are also human factors, mainly user improper operation, accidentally triggering the alarm, accidental intrusion, and accidental entry. Defense zone, etc. But according to industry sources, more than 95% of false positives are caused by humans.

Therefore, to reduce false alarms, it is indispensable to start from the aspect of civil air defense. The establishment of an alarm information confirmation mechanism can reduce the number of alarms. After the alarm center receives the alarm information, it should first send a confirmation signal to the alarm host, indicating that the center has received it, and the alarm host should resend it when it has not received the confirmation signal. In terms of technology, at present, various methods can be used to confirm the alarm signal, such as installing multiple detectors (usually using dual infrared + infrared plus microwave), when multiple detection heads detect intrusion signals at the same time, only send to the host Alarm signal, thereby reducing the false alarm rate.

In addition, the state can also formulate some regulations on false alarms. For example, some local government agencies abroad take measures such as inspection, fines, and punishment for alarm users or security companies. If the number of alarms exceeds the specified number within a certain period, a fine will be imposed. This can play a role in restricting human false alarms.

Of course, the establishment of an alarm confirmation mechanism and regulations is only a measure against human false alarms. How to reduce the false alarm rate of anti-theft alarms, including false alarms, involves many problems.

Improve the performance of infrared detectors in many ways

At present, there are mainly the following reasons for false / misreported alarm systems: wireless detectors have poor anti-interference ability, which is manifested as the same frequency interference is easy to cause false / misreported reports; infrared detectors are not accurate enough to rebel against intrusion, False / missing reports; infrared detectors are susceptible to temperature, light and other environmental factors and cause false alarms; wireless detector power supply systems do not effectively transmit information when power is low or low, making the detection distance of the detector shorter or It is caused by failure to work, resulting in false negatives.

Therefore, to reduce the false / misreport rate of the anti-theft alarm system, the most important thing is to improve the performance of the infrared detector from various aspects, including the selection of the detection head, the design of the Fresnel lens, the microprocessor program, the multi-discrimination technology, etc. Comprehensive factors determine the performance of the detector, otherwise it is easy to produce "short board effect".

For the anti-interference ability, the host can have a priority queuing process for the signal sent by the controller. Because it is impossible for each detector to transmit at the same time, the host sends two different signals that have been identified as two different times from the initial time to the detector, and queues up and temporarily stores the signals according to priority. This can greatly reduce co-channel interference and reduce its false alarm rate.

For the problem that the infrared detector has poor ability to judge the intrusion behavior and is susceptible to environmental factors such as temperature and light, the following measures can be taken: 1. Second delay judgment confirmation, that is, when the detector detects an intrusion signal, The behavior is determined for the first time without immediately sending a signal to the host. After the second confirmation of the existence of the intrusion behavior, an alarm signal is sent to the host. If the second confirmation of the intrusion behavior does not exist, the initial judgment result is cancelled and the detection state is returned, thereby reducing the false alarm rate. 2. Multi-probe head composite detection technology.


Equipped with multiple detection heads (dual infrared or infrared plus microwave), when multiple detection heads detect intrusion signals at the same time, the alarm signal is sent to the host, thereby reducing the false alarm rate. 3. Microprocessor program judgment. Analyze the signal collected by the probe through the program to further confirm whether someone has invaded. 4. Add a filter to the infrared detection head to filter out most of the non-human body's infrared wavelength spectrum, especially visible light.

The problem of power supply can allow the wireless detector to increase the undervoltage report function to remind the user to replace the battery in time; using the detector inspection technology, the detector is required to send a working status report signal to the host every few hours to let the host know the detection Whether the device can work normally, if the host computer does not receive the inspection signal within a period of time, it means that the detector cannot work normally. At this time, the host computer can remind the user to repair in a certain way in a timely manner.

In addition to the above points, when purchasing alarm system products, users should select products produced by regular manufacturers, and understand their specific functions, performance indicators and after-sales services in detail. When installing, please ask a professional person to install it, such as a manufacturer's engineering staff or someone with professional work experience, so as to avoid false / misreported due to improper installation. The detector should be installed to avoid the place where the wind, rain and electromagnetic interference are high and high temperature, and select an appropriate detection angle, and report to the manufacturer in time if problems are encountered.

The key to reducing the false alarm rate is to reduce the complexity of user use

According to the maintenance of the networked alarm centers and the experience with the alarm center, the cause of the false alarm is the first operation, such as the user does not disarm in time after going to work in the morning; the cause of the false alarm is the installation of the first, such as the installation of the mobile detector, which leads to too large a blind spot .

First, the key to reducing the false alarm rate is to reduce the complexity of user use. Specifically, developed countries have become accustomed to using alarm systems, and such systems in China are still in the early stages of promotion, and anti-theft systems have not yet become a habitual life behavior of people. In addition, there is still a contradiction between the convenience of use and the safety of the system of the alarm system products. Some products have good safety, but the operation is not convenient, or the product is easy to operate but the safety is not enough.

In fact, this is a market segmentation problem. Many excellent products such as C & K, ADEMCO, etc., are not developed for domestic household use. Whether they are suitable or functional, they only partially meet the needs of domestic users. Therefore, the market response is not good, especially in terms of use. According to our statistics, the usage rate of the alarm system installed in the home is far below 30%.

In this way, there is only one way out, which is to produce corresponding products for China's various needs. For example, the simple alarm kits on the market now have many loopholes in this type of product from a professional point of view, so they cannot be used as anti-theft systems at all. But this product is simple and easy to use. It can also solve the practical problems that many customers need, and it is of course accepted in the market. Therefore, I believe that the key to reducing the false alarm rate of the system is to redevelop the adapted products according to the needs of the Chinese market and eliminate the false alarms that account for the largest proportion from the source.

Secondly, the false alarms caused by product technical problems are mainly generated by mobile detectors and alarm control hosts. For the alarm control host, the main reason for the false alarms of the wireless alarm host is that the wireless coding methods matching the host and the detector are repeated. The detectors outside the fortified area and the detector's heavy codes in the area cause false alarms. Therefore, attention should be paid to the installation and debugging or the use of automatic coding code rolling rolling technology (but the cost is higher, currently only used for high-end wireless devices).

The main reason for the false alarm of the wired alarm control host lies in the design defects, which mainly depends on detecting the current change of the alarm defense loop to determine whether the defense area is triggered. For example, on some construction sites, it is found that the interference in the loop of the defense zone is very strong, which requires the host to filter well enough, otherwise the false alarms are continuous and the cause is generally not detectable; some wired alarm control hosts use open circuit alarms to avoid clutter interference And reduce costs, personally think that this is very undesirable. Even if no man-made damage is considered, once the wiring of the defense zone circuit with open alarm is short-circuited, the defense zone will fail, and the fault is extremely hidden, the host itself cannot be detected, and the fault found in actual use is often irrelevant.

Finally, the behavior of the state should be limited to the promulgation of regulations and enforcement of regulations, such as the introduction of regulations on the construction of networked alarm centers, deepening and increasing the intensity of the 3C certification work being carried out, the implementation of industry engineering inspection and acceptance, and the examination of the companies involved.

The technical lag of the detector is the weak link that causes the error and omission of the entire system

In recent years, advanced and reliable digital processing technology has been fully used in the control host of the alarm system and the receiving equipment of the center, and the technology has gradually matured. However, the most front-end equipment of the alarm system, like the detector, has not been a breakthrough in technology, but only through signal post-processing technology or through the combination of several detection technologies or the accumulation of a single technology to improve the stability of the system. It can be seen that the technical lag of the source of the alarm system (such as the detector) is the weak link that causes the error and omission of the entire system. Therefore, I think that it is the root of reducing the false / misreport rate of the entire anti-theft alarm system to solve the false / misreport phenomenon of the detector.

At present, among the wide range of detector products, passive infrared detectors are the most widely used. Below are some personal opinions on how to reduce the errors and omissions caused by infrared detection.

Before the breakthrough of traditional infrared detection technology, it is impossible to talk about solving the problems of false positives and false negatives. First of all, we should seek the source, which is a breakthrough from passive infrared sensors. By transforming the infrared source, the constant current source detection is changed to constant voltage source detection, thereby enhancing the strength of the signal and greatly improving the signal-to-noise ratio.

For example, Qing Rong Technology has recently developed PYROFLEX sensor technology. Through experiments and comparisons, the detector is tested for general walking. The signal detected is 10 times that of the general detection source, and the signal detected by running is 100 times the general detection source. ; The signal-to-noise ratio is high, the signal amplitude detected by the signal source is large, and there is no need to go through the operational amplifier circuit in the circuit design, so that the false alarm caused by the self-excitation of the arithmetic circuit is eliminated.

Secondly, like the SURESPOT signal processing technology, only the peak-to-peak signal processing is performed to effectively reduce the false negatives caused by the "zero drift" of the circuit. Because the general infrared source is not sensitive to rapid movement, PYROFLEX sensor technology can increase the detection of running signals by 100 times, which solves the problem of underreporting caused by the rapid pass of the general infrared source. For another example, the DFIR mobile infrared frequency division technology only reacts to the moving infrared heating element, so that it can avoid false alarms caused by environmental problems, such as heating, hot and cold air outlets, etc.

At the same time, the application of HIVIEW lens technology enables the detector to detect human bodies under high temperature conditions (above 28 ℃). When the temperature difference between the human body and the surrounding environment is not obvious, the temperature sensor in the lens starts to recognize the human body moving at 37 ° C within the height range of 1.6-1.8 meters, and the head of the human body is separately detected and processed, thereby greatly reducing leakage Newspaper.

Of course, in addition to solving the technical problems of the product itself, users should also consider the company's technical background, product production process, after-sales service and technical support when purchasing. At the same time, attention should also be paid to the installation environment and the technical level of the construction personnel.

Only by choosing good quality products, providing a good application environment, and cooperating with good construction technology can we truly reduce the false alarm and false alarm rate of the entire anti-theft alarm system.