Ceiling-mounted PIR sensors are common in offices and commercial spaces. However, they often have a dead zone directly below the sensor \u2013 you can stand right under it and not be detected.<\/p>\n
The Fresnel lens creates detection zones that project outward at an angle. Directly below the sensor, there are no zones. The size of the dead zone depends on mounting height and lens design.<\/p>\n
For a sensor with vertical field of view \u03b8_v, mounted at height H, the radius of the dead zone is approximately:<\/p>\n
R_dead = H \u00d7 tan(90\u00b0 – \u03b8_v\/2)<\/strong><\/p>\n Example: H=3m, \u03b8_v=90\u00b0, R_dead = 3 \u00d7 tan(45\u00b0) = 3m. So a 3m diameter circle directly below is blind.<\/p>\n Ceiling-mount sensors designed for the purpose often have lenses that create zones directly below.<\/p>\n Some ceiling-mount sensors can be tilted slightly to cover the area below.<\/p>\n Overlapping coverage from multiple sensors can eliminate dead zones.<\/p>\n A small, downward-facing PIR can cover the area directly below the main sensor.<\/p>\n Lower mounting height reduces the dead zone radius.<\/p>\n Dead zones under ceiling-mounted sensors are normal but manageable with proper lens selection and supplemental coverage.<\/p>\n","protected":false},"excerpt":{"rendered":" Introduction Ceiling-mounted PIR sensors are common in offices and commercial spaces. However, they often have a dead zone directly below the sensor \u2013 you can stand right under it and not be detected. Why the Dead Zone Exists The Fresnel lens creates detection zones that project outward at an angle. Directly below the sensor, there […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-4520","post","type-post","status-publish","format-standard","hentry","category-troubleshooting"],"blocksy_meta":[],"yoast_head":"\r\nSymptoms<\/h2>\n
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Solutions<\/h2>\n
Use a Sensor with 360\u00b0 Coverage and Proper Lens<\/h3>\n
Tilt the Sensor (If Possible)<\/h3>\n
Use Multiple Sensors<\/h3>\n
Add a Secondary Sensor<\/h3>\n
Lower the Mounting Height<\/h3>\n
Conclusion<\/h2>\n