How to choose the right detector?

Home security system setting, operation troubleshooting. Help installing wireless wired home security system.
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vedard
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Joined: Wed Dec 05, 2018 12:27 am

How to choose the right detector?

Post by vedard » Thu Feb 21, 2019 11:47 am

How to choose the right detector?
According to the place and area to be guarded against, different alarm probes are selected. Generally speaking, doors and windows can be installed with magnetic switches, bedrooms and living rooms with infrared microwave probes and emergency buttons, windows with glass breakage sensors, kitchens with smoke alarms.
Infrared Detector: Any object will emit different intensity of infrared radiation due to different surface heat. The wavelength of infrared radiation varies from object to object. Infrared detection is mainly used to detect human body and other intrusive moving objects. When human body enters the detection area, stable and constant thermal radiation is destroyed, resulting in a change of thermal radiation. After receiving, infrared sensors amplify, process and send out alarm signals.
Microwave Object Moving Detector: Using Doppler shift of high frequency radio wave as detection means, it is suitable for open space or square. Microwave is a kind of radio wave with very high frequency. Its wavelength is very short and it is easy to be reflected by objects. According to the frequency drift of incident and reflected waves, intrusive objects can be detected. Infrared microwave detector: It is one of the commonly used equipment in the alarm system. Its price is generally between 200 and 1600 yuan. Its working principle combines infrared and microwave. When infrared and microwave detectors have alarm signals at the same time, the probe will have alarm output, which reduces the possibility of false alarm. There are many types of infrared microwave probes, corresponding to different detection distances, some detect a sector area, some detect a narrow area (such as corridor), some are 360 degree detection, we must select the appropriate model according to specific needs, in order to achieve the effect. The sensitivity of the detector is generally adjustable.
Gate magnetic detector: It is a kind of detector which is widely used, low cost, easy to install, and does not need adjustment and maintenance. The gate magnetic switch is divided into movable parts and output parts. The movable parts are installed on the movable doors and windows, and the output parts are installed on the corresponding doors and windows. The installation distance between the two parts 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 into normal open.
Glass Breaking Detector: It uses piezoelectric microphone, which is installed in the position facing the glass. Because it only detects the high frequency glass breaking sound effectively, it will not be affected by the vibration of the glass itself.
Ultrasound Object Movement Detector: Ultrasound Object Movement Sensor needs a transducer capable of transmitting ultrasound and another transducer responsible for receiving. There is also a receiving and transmitting transducer on the body. Usually the transducer transmits a fixed frequency of ultrasonic wave, which is scattered in the detection space. If an object reflects the ultrasonic wave, its frequency will be offset, so as to detect whether there is an object moving. The detector is susceptible to vibration and airflow.
Infrared Counter-fire Detector: Detector using beam-blocking mode causes alarm when an invisible infrared beam is blocked when someone crosses the monitoring protection area. Usually used for outdoor wall alarm, it is always used in pairs: one transmitter, one receiver. The transmitter emits one or more beams of infrared light which can not be seen by human eyes, forming a warning line. When an object passes through, the light is blocked, the signal of the receiver changes, and the alarm is given after amplification. Infrared counter-fire probe should choose the appropriate response time: too short can easily cause unnecessary interference, such as birds flying through, small animals passing through, etc. too long will miss the report. The minimum shading time is usually determined at a speed of 10 meters per second. If the width of a person is 20 centimeters, the shortest interruption time is 20 milliseconds. More than 20 milliseconds alarm, less than 20 milliseconds no alarm.
Smoke Alarm Detector: There are photoelectric and ionic detectors. The former uses smoke to block the light path to send out alarms. The latter uses its own sensors to sense the concentration of ions in the air. Different sensors sense different gases (such as gas). The commonly used smoke sensor is designed to detect the concentration of carbon ions for fire prevention.
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