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What you should know about security alarm detectors
May 31, 2018

What you should know about security alarm detectors



Ⅰ. Classification of front-end security alarm detectors:


According to the installation of the detector can be divided into: wall, ceiling, mounting;


According to the detection range of the detector, it can be divided into: point-controlled alarm detector, wire-controlled alarm detector, surface-controlled alarm detector and space-prevention alarm detector.


In accordance with the working principle of detection can be divided into: infrared, microwave, composite, vibration, smoke, gas, glass broken, ultrasonic and so on.


According to the detection work methods can be divided into: active alarm detectors and passive alarm detectors.


Our common alarm detectors are: infrared alarm detectors, microwave alarm detectors, passive infrared / microwave alarm detectors, glass broken alarm detectors, vibration alarm detectors, ultrasonic alarm detectors, laser alarm detectors, magnetic switches Alarm detectors, switch alarm detectors, video motion detection alarms, sound detectors, and more. As shown below:


In practical applications, different types of alarm detectors can be reasonably selected to meet different security requirements according to different usage conditions.


As the most advanced detection part, the alarm detector has its sensitivity and reliability related to the stability of the entire anti-theft system. We need to combine various alarm detector working principles and applications to meet the needs of different customer groups based on the actual purpose of safety precautions and requirements.


The sensitivity and reliability of the alarm detectors influence each other. Reasonably configuring the detection sensitivity and using different anti-interference measures can improve the performance of the alarm detector. Therefore, to understand the performance and characteristics of various alarm detectors, according to different use environments, reasonable allocation of different alarm detectors is the key link of the anti-theft alarm system.


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Ⅱ. The principle and application of common alarm detectors:


1. Active infrared detector: It consists of an infrared transmitter and an infrared receiver. The infrared emitter emits a beam or most of the modulated infrared light toward the infrared receiver. When the emitter and receiver are obstructed, the receiver output signal changes and the detector alarms.

(It is widely used in surface perimeter protection systems)


2. Passive infrared detectors: There are two key components, one is Fresnel lens and the other is pyroelectric sensor. Any object above the absolute temperature (-273 degrees Celsius) in nature will produce infrared radiation, and the wavelengths of the infrared energy released by objects at different temperatures will also be different. The human body has a constant body temperature and differs from the ambient temperature. When the human body moves, this change in the difference is detected by the pyroelectric sensor through the Fresnel lens, thereby outputting an alarm signal.


(It's mainly used for indoor intrusion by outsiders.) It reminds me of the thermal imaging camera that became popular in the United States when it hit Iraq.


3, microwave detector: Its application is the principle of Doppler effect. In the microwave section, when transmitting at a frequency, when the emitted microwave encounters a fixed object, the frequency of the reflected microwave is not changed, ie, the signal is emitted and the detector does not send an alarm signal. When the microwave that is launched meets a moving object, the reflected microwave frequency will change, that is, the microwave detector will send an alarm signal.

Didn't bats come to night on this one?


4. Vibration detector: As the name implies, it detects the vibration signal generated by the intruder during various sabotage activities as an alarm basis. For example, when a wall is broken, a hole is drilled, an ATM is destroyed, a safe is damaged, etc., the vibration of these objects can be caused.


5. Dual-element infrared detectors and four-element infrared detectors: Two detectors with two detectors whose performance is the same and whose polarities are reversed are integrated into a dual detector. The four-probe detector is a four-probe detector that integrates four pyroelectric sensors with the same performance and opposite polarities.


6. Dual tech detector: In order to overcome the defects of the single technology alarm detection technology, two kinds of detectors with different technical principles are usually integrated together, and only when the sensors of the two detection technologies detect the movement of the human body Known as double detector.

The common dual tech detector on the market is microwave + passive infrared.


7. Tri Tech detectors and multi-detectors: Many manufacturers use microprocessors to perform technical analysis of alarm collection information and then integrate them into a detection method. Ever since then, there have been three Jian detectors and multiple detectors. Its main core is technical analysis.


However, the true Tri Tech detector must possess three detection technologies, such as passive infrared + microwave + ultrasonic detectors. Taking out pets, analysis of intrusion directions, etc. are all means of technical analysis.



To sum up:


According to the actual environment and the user's security requirements, a reasonable selection and installation of various alarm detectors can better achieve the purpose of security.


Therefore, during the actual installation process, the detector must not only have tamper-proof and anti-destroy functions, but also prevent humans from short-circuiting or disconnecting the transmission line (see: Working Principles of Wired Security Alarm System and Common Connection Modes).



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