c) Dual-Technology Sensors - Combines infrared and ultrasonic technologies into
a single housing. Dual-technology sensors are good for areas where a single technology
O.S. has difficulty of detecting human movement and where one or the other technology is
prone to false activation.
d) New Technology - Although ultrasonic and PIR technologies remain
predominant for occupant sensing, a new passive dual technology sensor has recently
entered the market. This device combines PIR with an active listening system. After the
PIR detects someone entering the area, the microphonics take over. This sensor's
applications include office spaces with cubicles and large restrooms. Microwave motion
sensors exist for security system applications. Do not use microwave sensors for occupant
detection since microwaves pass through most building materials and will detect
movement beyond the desired coverage area.
1.02 Mounting Methods - Sensors are designed for two principal mounting methods: wall
switch replacement and ceiling mount.
a) Light Switch Replacement - Direct replacement of a wall switch with a PIR
O.S. will likely only be acceptable in smaller rooms where no partitions obstruct the
sensor's view of the movement of the room's occupants. These wall switch replacement
units can control only the lighting fixtures connected to the switch. To avoid false
activation, manual turn-on, automatic turn-off is recommended. In private offices, this
would also preclude activation by someone just dropping off mail, plans, etc. Manual
turn-on is also beneficial where available daylight allows electrical lighting system to
remain off for several hours at a time.
b) Ceiling Mount - Available in infrared, ultrasonic, and dual-technology. Use for
large area coverage and rooms with partitions and other obstructions. Ceiling mounted
O.S. connect to lighting system through transformers and relays to operate a large number
of lighting fixtures.
1.03 Proper O.S. Location - Improper location is the most significant factor in O.S.
misapplication. Locate sensor so that it will not detect movement outside the desired
coverage area through an open doorway. In many cases, wall switch replacement O.S. are
ineffective because the existing wall switch location is behind a partition or on the wrong
side of a wall, limiting motion detection to a very small part of the desired coverage area.
1.04 Compatibility - Be sure O.S. is designed to control the type of lighting system you
have chosen for new projects or for the existing lighting system in a renovation project.
Not all sensors will work with fluorescent loads having standard or electronic ballasts or
with compact fluorescent lamps. Use O.S. with rapid start fluorescent ballasts,
particularly with short "off" times (five minutes). Do not use O.S. with instant start
fluorescent ballasts, unless "off" time is very long (30 minutes, minimum), since lamp life
will be shortened. Before specifying O.S. with High Intensity Discharge (HID) lighting,
check with O.S. manufacturer and HID lamp and ballast manufacturer for application data.