PIR motion sensors are most effective when mounted in what orientation relative to the expected intruder path?

PIR motion sensors are most effective when mounted in what orientation relative to the expected intruder path?

• A. facing the intruder directly
• B. mounted on the ceiling above an entry
• C. so the intruder walks across the unit
• D. placed near a heat source

Answer: (C)

PIR sensors detect motion by measuring changes in infrared energy across two sensing elements. They work best when a warm body moves across the sensor’s field of view, so the heat signature crosses the two elements in sequence. As the intruder walks across the unit, one element senses the rise in infrared before the other, creating a clear differential signal that reliably triggers. If the intruder moves directly toward or away from the sensor, both elements change almost in sync, producing a weaker differential and a greater chance of missing motion. So orienting the sensor so the expected path crosses the sensing plane yields the strongest, most reliable detection. Avoid placements that place the sensor near heat sources, which can cause false alarms or desensitization.

PIR sensors detect motion by measuring changes in infrared energy across two sensing elements. They work best when a warm body moves across the sensor’s field of view, so the heat signature crosses the two elements in sequence. As the intruder walks across the unit, one element senses the rise in infrared before the other, creating a clear differential signal that reliably triggers. If the intruder moves directly toward or away from the sensor, both elements change almost in sync, producing a weaker differential and a greater chance of missing motion. So orienting the sensor so the expected path crosses the sensing plane yields the strongest, most reliable detection. Avoid placements that place the sensor near heat sources, which can cause false alarms or desensitization.