Burglar alarm detector application common sense


Depending on the place and area to be guarded against, different alarm probes are selected. Generally speaking, doors and windows can be installed with door magnetic switches, bedrooms and living rooms with infrared microwave probes and panic buttons, windows with glass break sensors, and kitchens with smoke alarms.

Infrared detector: Any object will radiate infrared rays of varying strengths due to the different degrees of surface heat. Due to the different objects, the wavelength of the infrared radiation is also different. Infrared detection is mainly used to detect the human body and some other invasive mobile objects, when the human body into the detection area, the stability of the unchanged thermal radiation is destroyed, resulting in a change of thermal radiation, infrared sensors to receive the amplification, processing, sending alarm signals.

Microwave object movement detector: the use of high-frequency radio waves Doppler shift as a means of detection, suitable for open spaces or squares. Microwave is a very high-frequency radio waves, the wavelength is very short, easy to be reflected by the object, according to the frequency drift of the incident and reflected waves, you can detect the intrusion of objects.

Infrared microwave detector: It is one of the commonly used equipment in alarm system, and its price is usually between 200~1600 RMB. It works by combining infrared and microwave in one. When the infrared and microwave detectors have alarm signals at the same time, the probe will only have alarm output, reducing the possibility of false alarms. Infrared microwave probes have a variety of models, corresponding to different detection distances, some detecting a fan-shaped area, some detecting a narrow lot (such as corridors), and some are 360-degree detection, be sure to choose the right model according to the specific needs of the results. The sensitivity of the detector is generally adjustable.

Door Magnetic Detector: It is a widely used, low-cost, easy-to-install, and does not require adjustment and maintenance. Door magnetic switches are divided into moveable parts and output parts. The movable part is installed on the movable door or window; the output part is installed on the corresponding door or window, and the installation distance between the two is not more than 10mm. There are two lines on the output part, the normal state is normally closed output, the door and window open more than 10 mm, the output is converted to normally open.

Glass breakage detector: it uses piezoelectric micro-sounders, installed in the position facing the glass, because only the high-frequency sound of glass breakage is effectively detected, so it will not be subjected to the vibration of the glass itself to cause a reaction.

Ultrasonic object movement detector: Ultrasonic object movement sensors require a transducer capable of transmitting ultrasonic waves and another transducer responsible for receiving them, or the receiving and transmitting transducers are coexisting in one body. Normally the transmitting transducer sends out ultrasonic waves at a fixed frequency and spreads them out in the detected space. If an object reflects back the ultrasonic waves, its frequency will be shifted, thus detecting whether there is any object movement. The detector is susceptible to vibration and airflow.

Infrared convection detector: the use of beam blocking detector when someone crosses the monitoring of the protective zone, blocking the invisible infrared beams and triggering the alarm. Commonly used in outdoor fence alarms, it is always used in pairs: one transmitter, one receiver. The transmitter sends out one or more beams of infrared light that cannot be seen by the human eye, forming a cordon, an object passes through, the light is blocked, the receiver signal changes, amplification and processing of the alarm. The infrared countermeasure probe to choose the appropriate response time: too short to easily cause unnecessary interference, such as small birds flying over, small animals through, etc.; too long will occur underreporting. Usually 10 m / s to determine the shortest shade time. If the width of the person is 20 cm, then the shortest blackout time is 20 milliseconds. Greater than 20 milliseconds alarm, less than 20 milliseconds no alarm.

Smoke alarm detector: there are two types of photoelectric and ionic, the former use smoke to block the light path to send an alarm, the latter use their own sensors, sensing the concentration of ions in the air, different sensors sense different gases (such as gas), commonly used in order to fire prevention and set up to detect the concentration of carbon ions in the smoke sensor probes.

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