Motion Sensor

A PIR motion sensor does not emit any signal to detect movement. It passively reads infrared energy, the heat given off by anything warmer than the surrounding room, across its field of view. When a warm body moves through that field, the sensor registers a change in infrared pattern and sends a signal to the command panel.

Pet-immune models solve the biggest complaint about older motion sensors: false alarms from cats and dogs. They use a weight and height calibration that filters out infrared patterns consistent with a pet moving near the floor, typically up to 40 to 80 pounds depending on the model, while still catching a person walking through the same space.

The strongest placements are choke points a person has to cross to reach valuables: the main hallway, the stairs, and the room connecting an attached garage to the house. A single well-placed sensor in a central hallway often covers more real intrusion paths than several sensors scattered in individual rooms.

Avoid aiming a sensor at a window, a heating vent, or a radiator. Direct sunlight and blowing warm air both mimic the infrared signature the sensor is watching for, which causes nuisance alarms. A professional installer tests each sensor's actual coverage angle during installation rather than relying on the manufacturer's stated range alone.