Passive infrared (PIR)
PIR technology senses occupancy by detecting the difference between heat emitted from the human body in motion and the background space. PIR sensors require an unobstructed line-of-sight for accurate detection. These sensors utilize a segmented lens which divides the coverage area into zones. Movement between these zones is interpreted as occupancy. Generally, PIR sensors are good at detecting major motion (e.g. walking) and work best in small, enclosed spaces with high levels of occupant movement.
considerations:- Ensure a clear line-of-sight between the lens and the location of the activity
- Ensure that there is a discernable temperature difference between occupant and ambient temperature
|
 | best for use in areas with:
- an unobstructed view
- high air flow
- ceiling fans
|
Ultrasonic (US)
Ultrasonic technology senses occupancy by bouncing ultrasonic sound waves (32kHz – 45kHz) off objects in a space and detecting a frequency shift between the emitted and reflected sound waves. Movement by a person or object within the space causes a shift in the wave frequency, which is interpreted as occupancy. Ultrasonic occupancy sensors are good at detecting minor motion (e.g. typing, reading) and do not require an unobstructed line-of-sight, thus making them suitable for applications such as an office with cubicles or a restroom with stalls.
considerations:- Do not place within 6ft. of HVAC as this may cause false triggering
- Avoid placement facing doors or exits as coverage may spill into adjacent areas
|
 | best for use in areas with:
- low air flow
- partitions and dividers
- a high level of minor motion
|
Dual technology (DT)
Dual-technology occupancy sensors use both passive infrared and ultrasonic technologies for maximum reliability. These sensors also minimize the risk of false triggering (lights coming on when the space is unoccupied). Both US and PIR technologies must detect occupancy to turn lighting on, while continued detection by only one technology will keep lighting on.
|
 | best performing sensor |