|Occupancy sensors will automatically turn
lights on when they sense that someone is
coming into an area and then turn them off
when they sense that the space is empty.
They are most effective when they are used
in rooms that are not in constant use, such
as attics, basements, garages, closets, bathrooms
and storage areas. These sensors can substantially
reduce energy costs because they make sure
that lights are not left on unnecessarily
for long periods. Occupancy sensors can usually
pay for themselves within two to three years.
They are installed on either the wall or
ceiling of the room.
There are three basic types of sensors: ultrasonic
motion detectors, infrared heat sensors,
and audio sensors. If you are thinking of
buying an occupancy sensor, consider the
- Ultrasonic sensors use quartz crystals that
radiate high frequency sound waves, which
cannot be heard by the human ear. The waves
are emitted into the monitored area, where
they bounce off the objects and people in
the space. The sensor measures the frequency
of the waves, and small changes in frequency
caused by motion activate the sensor.
- Infrared heat sensing sensors detect changes
in the infrared heat radiated in the monitored
area. The sensor is controlled by low voltage
wiring. They work best in small areas where
no obstructions block the sensing field.
Sudden changes in temperature (such as the
entrance of a warm body into the sensing
field) triggers the sensor, so look for models
with a daylight filter to prevent sun rays
from triggering the sensor.
- Audio sensors work by monitoring the sound
levels in the area with a microphone. A noise
activates the sensor
No matter which type sensor you buy, you
will get the best results if you look for
models that can be adjusted for both time
delay and occupancy sensitivity.