The main function of a wireless motion sensor alarm is to detect motion in a specific area around it. The motion sensor detects rapid motion through infra red rays which are incident on it. Whenever you are thinking of installing a motion sensor in your home for security, it is best that you have a thorough understanding of the functioning of a motion detector so that you can use it without problem and avoid mishaps. The infrared rays which are used to detect motion are focused through a Fresnel lens. A Fresnel lens is made out of a material which is totally transparent to radiation and has a thickness ranging from eight to fifteen micrometers. If we go more in to the detail of the Fresnel lens, it is a plano-convex lens in which the convex part is made thinner.
The function of the convex part is to focus infra red radiation on a crystal which is extremely sensitive to changes in infrared radiation. The range of the thickness of the lens mentioned above is used specifically in order to detect any human movements. If this is not the case, the sensor might not be able to differentiate between a human and a fly which can result in false alarms. False alarms can be really annoying and they have an adverse impact on the effectiveness of the wireless alarm. The crystal is the main sensor as it can respond to slightest movements as there will be change in the infrared radiation incident on it.
Movement also produces a change in heat which is measure in order to know the speed of the movement taking place. The change in heat produces electrical signals which are then directed into a proper electrical circuit. By inculcating the heat change into the electrical circuit, the pulse width and the rapidity of change are measured. However, you might be wondering how the sensor makes sure that the heat from surroundings like temperature changes or changes in the environmental heat are not mistaken for heat due to movement. In order to avoid the wireless alarm system being triggered by heat changes other than those produced by human motion, special sensors are installed which monitor more ambient temperature and heat changes.
The differentiating factor between human movements and environmental heat changes is the rapidness with which the change in radiation takes place. The electrical circuit within the detector is designed in such a manner that it only rapid changes in motion are detected which result in rapid changes in electrical signal output. After the change in motion is detected through this mechanism, there are device in the wireless motion sensor alarm which relay radio signals and activate the alarm or any other programmed response.
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