Description: Passive infrared sensors detect electromagnetic radiated energy generated by external sources, particularly the thermal energy emitted by people in the far infrared range.
Active infrared sensors generate a multiple beam pattern of modulated infrared energy and react to a change in the modulation of the frequency, or an interruption in the received energy.
Classification: Active / Passive - Overt - Line of Sight
Application: Can be used to provide secondary levels of protection or to cover gateways & openings etc., isolated local alarm cover to vulnerable areas, triggers for CCTV Cameras etc. Passive infrared sensors are often wired in a multi beam configuration for more reliable operation.
Advantages: Low cost, easy to deploy & maintain.
Possible Causes of Nuisance Alarms: Overgrown vegetation, fog, heavy rain, snow, sand storms, moving objects, animals, birds and debris, movement of mounting posts, severe temperature changes.
Methods of Defeat: Blind Spots, tunnelling or bridging.