Occupancy Sensors 101

About Sensing Technologies

Passive Infrared (PIR)
Infrared occupancy sensors are passive devices designed to detect the movement of heat-emitting bodies. They are installed to monitor areas where there are no physical obstructions to block the sensor's field of view.

HOW IT WORKS: People naturally emit a small amount of infrared heat. As a person passes through the field of view, the sensor detects the motion as a change in the infrared background and responds by switching on area lights. After the field of view is unoccupied for a user-defined delayed-off time, the sensor will automatically turn off the lights.

Ultrasonic (US)
Ultrasonic sensing technology provides highly accurate small-motion detection. Leviton sensors employing ultrasonic technology are well suited to monitoring areas, especially smaller or narrow ones, with inanimate objects (such as furniture) that block the line of site and hence are likely to block the field of view of PIR sensors. They are also ideal where more sensitive detection is required.

HOW IT WORKS: Ultrasonic occupancy sensors generate high frequency sound waves beyond the capability of human hearing, due to the Doppler Effect. These controls are active: continually emitting sound waves and monitoring changes in the return time of the reflected sound waves. Movement in the sound wave field causes a change in wave frequency and the sensor responds by switching on area lights. When the change in frequency is no longer detected after a delayed-off time, the sensor turns off the lights. Leviton ultrasonic sensors operate at a frequency outside the range of most hearing aid products and will not interfere with their ability to operate properly.

Multi-Technology
Multi-Technology occupancy sensors ultrasonic sensing for maximum sensitivity with PIR technology to prevent false triggers from air conditioning and corridor activity. These sensors are ideal for large, open areas including office areas with cubicles, general workspaces, warehouse and storage facilities, cafeterias, and public areas in commercial facilities.

HOW IT WORKS: Leviton multi-technology sensors utilize both sensor technologies to determine when to turn the lights off.

Adaptive Definition
A dedicated internal microprocessor continually analyzes the room environment and adjusts itself automatically. The internal timer, detection sensitivity and thresholds are automatically adjusted. Once installed, a sensor incorporating adaptive technology should never require manual adjustment or calibration.

Selection & Placement

Sensors can be mounted in the middle of walls, in corners, or on ceilings. Occupancy sensors must be intelligently placed in order to ensure that motion is detected throughout an entire space. With a variety of models from which to choose, care should be taken to select the proper combination of sensors to cover an entire area with motion detection.

Factors to consider before selecting and placing an occupancy sensor include:

• Size and shape of area needing coverage compared to ranges of occupancy sensors
• Obstacles that may block the sensor's line of sight
• How much activity there is in a space
• Ceiling height
• Airflow that can falsely register as motion
• Location of HVAC ducts

Select a Centura-compatible occupancy sensor when installing an occupancy sensor within a Centura Energy Management System. In this case, the CN100 Power Pack provides power to the occupancy sensor (no OSPXX is required). Please note that Centura's Dimming Power Pack also has its own built-in HVAC relay.

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