How to avoid false alarms of anti-theft alarm system!

A few days ago we learned about the working principles and common connection methods of the wired security alarm system, and learned about the host and connection methods in the alarm system.

Today we mainly study some of the summary of the application of the system program, a set of overall alarm system, in the practical application will always encounter this or that problem. Especially based on false alarms. How do you define this false alarm? What does this have to do with our actual installation process? Today we come one by one.

Definition of false alarm

With regard to false alarms, there is currently no authoritative definition. In our country, it is generally considered that: "No dangerous situation alarm system sends an alarm signal is false alarm."

According to this definition, the false alarm rate of the alarm system (in a certain period of time, the ratio of the number of false alarms to the total number of alarms) is generally above 95%.

The definition of false alarms in some western countries is: “False alarms are alarm signals that do not require the police to actually send police to the actual situation, but do not include those caused by adverse natural climate and other special environments that cannot be manipulated by alarm companies and users. Alarm signal."

According to this definition, the U.S. UL standard states: "Each alarm system can only have four false alarms per year."

The reason of false alarm

Alarm caused by malfunction of alarm equipment

Under the specified conditions, the product can't complete the specified function within a specified time, which is called failure. The types of failures are damaging and drifting.

Damaged failures include all failures of performance and abrupt failures. Such failures are usually caused by the damage of components or poor production processes (such as welding).

Drift fault refers to the fault caused by the drift of the parameters of the components and the supply voltage. For example, too high a temperature will cause a change in the resistance value of the resistor. At this time, the device will perform better or worse. In fact, factors such as ambient temperature, component manufacturing process, equipment manufacturing process, usage time, storage time, and power supply load may cause changes in the component parameters and cause drift faults.

Whether it is a damaging fault or a drift fault, it will make the system false alarms. To reduce the false alarms that result from this, efforts should be made from the following aspects.

(1) The production enterprise of alarm equipment must improve the design level and technological level of the product. At the same time as the system design, it must also be designed for reliability, such as redundant design, electromagnetic compatibility design, and three-proof design (moisture protection, salt protection) Fog, anti-fungal, drift reliability design, etc. On this basis, improve the reliability of product manufacturing processes, such as the strict screening of component quality; strict quality supervision and management of the production process, to ensure that product quality meets the requirements of the relevant standards.

Units or individuals that sell alarm equipment shall carry out strict incoming inspections. The contents of the inspection shall be: certification of product quality inspection; production license of industrial production enterprise or safety certification certificate or production registration approval letter.

(2) The management department shall regularly or irregularly organize inspections and random inspections of the security market, and discover that illegal activities in the production and sale of security product activities shall be handled in strict accordance with the provisions of the “Administrative Measures for the Prevention of Security Technology Products”.

(3) The construction unit (user) of the alarm system shall clearly require the construction unit to use the products that have been inspected by the authorized testing agencies in the corresponding project documents; the foreign equipment shall use the products that are imported from the regular channels and inspected according to international advanced standards.

(4) In order to ensure the good working condition of the alarm system, a regular inspection and maintenance system must be established. By the way, at present, the maintenance methods of China's alarm system need to be resolved, and it is best to repair the variable-construction unit as the maintenance of a professional maintenance company. This is not only beneficial to the use of maintenance resources (maintenance personnel, maintenance equipment, maintenance spare parts, etc.) The improvement of the maintenance level, more importantly, can improve the reliability of the security system.

Incorrect alarm caused by improper design and construction of alarm system

Incorrect alarm due to improper system design

Equipment selection is the key to the system design. There are a wide variety of alarm equipments. Each has its own characteristics, application scope and limitations. Improper selection can cause false alarms. For example, the use of seismic detectors close to the source (airfield, railroad) can easily cause false alarms; the use of ultrasonic detectors in places where bats are frequent causes false alarms. This is because bats emit ultrasonic waves; High-frequency sounds, such as ring tones and metal impact sounds, can cause false alarms for single-technology glass break detectors. Therefore, to reduce false alarms caused by improper equipment selection, system designers must be familiar with the principles, characteristics, and scope of application of various alarm devices. And limitations. At the same time, we must also grasp the on-site environmental conditions, climate conditions, electromagnetic field strength, and changes in illuminance in order to select alarm equipment according to local conditions.

In addition to the selection of equipment and equipment, the improper design of the system also manifests itself in the equipment installation location, installation angle, protective measures and system wiring. For example, when a passive infrared intrusion detector is installed facing an air conditioner or ventilation fan, it will cause a false alarm of the system; if an active outdoor infrared detector is not used for proper sun protection (the sun shield is also best for protection), it is bound to Caused by the system of false alarms; alarm lines and power lines, lighting lines and other strong electric circuit spacing is less than 1.5m, and without adding anti-electromagnetic interference measures, the system will also generate false alarms.

Misuse caused by improper construction

This part of the problem is mainly manifested in the following aspects:

(1) No strict construction according to design requirements.

(2) Improperly installed equipment or improper inclination.

(3) Solder joints have vacant welds, burrs, or shielding measures.

(4) The sensitivity of the device is poorly adjusted.

(5) Inspection equipment for construction 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 safety supervision system as soon as possible. This will help improve the quality of the project and reduce the number of false alarms due to construction.

Environmental alarm caused by false alarm

The false alarm caused by the environmental nuisance refers to the alarm system being generated under normal working conditions. It is unavoidable from the principle, but the facts are not needed and it belongs to false alarm. For example, thermal airflow causes false alarms from passive infrared intrusion detectors; high-frequency sounds cause false alarms from single-technology glass break detectors; and ultrasonic sources cause false alarms from ultrasonic detectors. The most effective measure to reduce such false alarms is to use dual detectors (two different detectors detect the “target” at the same time, and the alarm only sends an alarm signal). The current products include: microwave-passive infrared double detector, voice-activated glass broken double detector, ultrasonic-passive infrared double detector and so on. However, some environmental noise detectors have been used as a force, for example: rats are in the protection zone; pets are walking indoors and so on. To this end, scientists and technicians have introduced micro-processing technology into the alarm system to enable them to have a certain ability to discriminate and think, and to judge to some extent whether it is an intruder or an alarm caused by environmental noise.