Causes of false alarms in the anti-theft alarm system

In the security information, there are many technical articles of security products. This article mainly discusses the problem of the false alarm caused by the anti-theft alarm system in the security products to the user. In order to develop low-false positive products, scientific and technological personnel have made great efforts, and their effects have been remarkable. But false alarms still exist. Where is the problem? And how to solve them? The article on the above problems analyzes the reasons and solutions of false alarms produced by the current anti-theft alarm system more comprehensively for the reference of the industry.

There is currently no authoritative definition of false alarm. In our country, it is generally believed that: "the alarm signal is issued by the anti-theft alarm system without a dangerous situation. It is a false alarm." According to this definition, the false alarm rate of the alarm system (within a certain period of time) , The ratio of the number of system false alarms to the total number of alarms) is generally above 95%. In some western countries, the definition of false alarm is: "false alarm refers to the alarm signal that the police does not need the police to actually dispatch the police, which does not include those caused by the harsh natural climate and other special environments that cannot be manipulated by the alarm company and the user. Alarm signal. "According to this definition, the US UL standard stipulates:" Each alarm system can only have up to four false alarms per year. "

The above two definitions are from different perspectives, and each makes sense. Due to the limitation of the text, only the former definition is used to analyze the causes of false alarms of the anti-theft alarm system, so as to formulate practical and feasible measures to reduce false alarms.

  1 False alarm caused by malfunction of anti-theft alarm device

The failure of a product to perform a specified function under specified conditions and within a specified time is called a failure. The types of failures are destructive failures and drifting failures. Destructive failures include total failure and sudden failure of performance. Such failures are usually caused by component damage or poor production processes (such as virtual soldering, etc.).

Drift faults refer to faults caused by the drift of component parameters and power supply voltage. For example: too high temperature will cause the resistance value to change, at this time the device behaves from good to bad. In fact, factors such as ambient temperature, component manufacturing process, equipment manufacturing process, use time, storage time, and power load may cause changes in component parameters, resulting in drift failures. Whether it is a destructive fault or a drift fault, the system will falsely alarm. To reduce the resulting false alarms, efforts should be made from the following aspects.

(1) The manufacturer of anti-theft alarm equipment must improve the product design level and process level. At the same time as the system design, it also needs to make reliability design, such as redundancy design, electromagnetic compatibility design, three-proof design (moisture-proof, anti-proof) Salt spray, anti-mold), drift reliability design, etc. On this basis, improve the reliability of the product manufacturing process, such as strict screening of component quality; strict quality supervision and management of the production process, etc., to ensure that product quality meets the requirements of relevant standards.

Units or individuals that sell anti-theft alarm equipment should conduct strict purchase inspections, which include: product quality inspection qualification certificates; industrial production licenses or safety certifications or production registration approvals of manufacturing enterprises.

(2) The management department should regularly or irregularly organize inspections and spot checks on the security market, and discover violations in the production and sale of security products should be dealt with in strict accordance with the provisions of the "Administrative Measures on Security Technology and Preventive Products".

(3) The construction unit (user) of the anti-theft alarm system should clearly require the construction unit to select the products qualified by the authorized testing agency in the corresponding engineering documents; the foreign equipment should use the products imported from regular channels and qualified according to international advanced standards.

(4) In order to ensure the good working condition of the anti-theft alarm system, a regular inspection and maintenance system must be established. By the way, at present, the maintenance method of the alarm system in China needs to be resolved. It is better to change the maintenance of the engineering contractor to a professional maintenance company. This is not only conducive to the use of maintenance resources (maintenance personnel, maintenance equipment, maintenance spare parts, etc.) and The improvement of the maintenance level is more important to improve the reliability of the security system.

2 False alarms caused by improper alarm system design and construction

2.1 False alarm caused by improper system design

Equipment selection is the key to system design, and there are many types of alarm equipment, each with its own characteristics, scope of application and limitations. Improper selection will cause false alarms. For example, the use of vibration detectors close to the source of the earthquake (airfield, railway) can easily cause false alarms of the system; the use of ultrasonic detectors in places where bats often appear also makes the system false alarms, because the bats emit ultrasonic waves; High-frequency sounds such as ringtones, metal impact sounds, etc. can cause false alarms of single-tech glass break detectors ... Therefore, to reduce false alarms caused by improper selection of equipment, system designers must be very familiar with the principles and characteristics of various anti-theft alarm equipment , Scope and limitations. At the same time, we must also grasp the on-site environmental conditions, climatic conditions, electromagnetic field strength and illuminance changes, etc., so as to choose the alarm equipment according to local conditions.

In addition to the selection of equipment and equipment, improper system design is also reflected in the installation location, installation angle, protective measures and system wiring of equipment and equipment. For example: when the passive infrared intrusion detector is installed against the air conditioner or the ventilator, it will cause false alarms of the system; if the outdoor active infrared detector is not provided with proper sun protection (the best protection is also provided with a sunshade), it is bound to be False alarm caused by the system; when the distance between the alarm line and the power line, lighting line and other strong current lines is less than 1.5m, without the measures to prevent electromagnetic interference, the system will also generate a false alarm ...

2.2 False alarm caused by improper construction This part of the problem mainly manifests in the following aspects:
(1) The construction is not strictly in accordance with the design requirements.
(2) The equipment is not installed firmly or the inclination angle is inappropriate.
(3) The solder joint has virtual soldering, burrs, or shielding measures are not appropriate.
(4) The sensitivity of the equipment is poorly adjusted (5) The construction testing equipment does not meet the measurement requirements.

The solution to the above problems is to strengthen the supervision and management of the construction process and implement the security engineering supervision system as soon as possible, which is very conducive to improving the quality of the project and reducing false alarms caused by the construction link.

3 False alarms caused by improper use by users

Improper use by users often causes false alarms in the alarm system. For example: the window with door magnetic switch is not inserted, and it is blown open by the wind at night; the staff enters the warning area by mistake; the emergency alarm device is accidentally triggered; the system check-in staff misuses it; The cause of the system false alarm. Analyzing the user's improper use, clarifying the error, and improving the user's level can greatly reduce the number of false alarms of the alarm system.

4 False alarms caused by environmental noise

The false alarm caused by environmental noise refers to the alarm system generated under normal working conditions, which is unavoidable in principle, but the fact is not needed, and belongs to false alarm. For example: hot air currents cause false alarms for passive infrared intrusion detectors; high-frequency sounds cause false alarms for single-technology glass break detectors; ultrasonic sources cause false alarms for ultrasonic detectors, etc. The more effective measure to reduce such false alarms is to use dual-detector detectors (the detectors with two different principles detect the "target" at the same time, and the alarm will send out an alarm signal). The current products are: microwave-passive infrared double discriminator, voice-controlled vibration glass breaking double discriminator, ultrasonic wave-passive infrared double discriminator, etc. However, some environmental noise double-detector detectors are powerless, for example: rats are infested in the prevention zone; pets are walking around in the living room. To this end, scientists and technicians have introduced micro-processing technology into the alarm system, so that they have a certain identification and thinking ability, to a certain extent can judge whether it is an intruder or an alarm caused by environmental noise.

With the development of sensor technology and computer technology, the popularization and application of large-scale integrated circuits, the alarm system will continue to be more intelligent, and the false alarm phenomenon caused by environmental noise will be reduced.