Your motion sensor has a dial, called either "Sensitivity" or "Range," that allows you to calibrate how readily movement triggers it. To really tame a motion-detecting security light that's coming on whenever a cat strolls through its range or a warm car engine happens by, you also need to point the sensor optimally. Movements of animate objects coming straight toward the sensor are less likely to trigger the sensor than movements going across the detection zone, so install the sensor at a 90-degree angle to the zone.
Setting the Sensitivity Control
This dial may be on the bottom or the back of your motion sensor. If it's on the back of a decorative lantern, you'll need to lift it off its junction box to adjust it.
During your initial setup, set the dial halfway between the "Min" and "Max" positions, at 12 o'clock.
Test the sensor by walking across the detection zone -- the area you want the sensor to monitor. Adjustments to the sensitivity setting -- in effect, a "range" setting -- tell the unit how far away to check for movement.
Adjust your results by mounting a ladder to repoint the sensor lower or away from warm objects such as heat vents to minimize the detection zone.
Repeat your tests, walking in front of the sensor and setting the dial back as needed by twisting it counterclockwise toward the "Min" mark, until you are satisfied with the responsiveness of the unit.
You may encounter false triggers from heat sources including the outdoor condenser unit of a central air conditioner, heat vents, swimming pools or large sunny expanses of driveway. If so, reset the sensitivity dial closer to "Min."