G. Sheppard, Browndeer, WI Congratulations on your company's decision to save energy. You'd be surprised at how few companies invest in efficiency improvements. Occupancy sensors can produce significant savings where facilities are infrequently used, and that appears to be your company's case. Two popular types of occupancy sensor technology exist. One relies on infrared detection and the other is based on ultrasonic waves.
Infrared sensors detect body heat and movement.
A clothed body emits heat primarily from the person's head and hands. Infrared sensors monitor a wedge-shaped room envelope for changes in thermal energy at a specific height. A special lens divides the wedge into sensor zones. As a person moves across a room, the sensor detects the change in each zone's heat pattern, causing an internal relay to switch the room's lights on. If no changes in pattern occur in the monitored area for a preset span of time, somewhere between 5 seconds and 15 minutes, the sensor responds by switching the lights off.