Occupancy sensors turn on lights automatically when a room is occupied or when motion is detected. These motion sensors are ideal for offices, classrooms, bathrooms, warehouses, bathrooms, and other industrial and commercial applications. Occupancy sensors detect when a person comes inside a room or space and automatically activates the light. When no motion is detected, it turns off the light automatically as well until the next motion is detected.

Occupancy sensors provide huge energy and cost savings by limiting the time the lights are on to only when they are needed. Different technologies are used to detect motion to maximize the accuracy and effectivity of the sensor.


Passive Infrared (PIR) Technology

Passive infrared technology uses human body temperature to sense occupancy or movement in a room. As a person moves across its switching zones, a change in temperature is detected that triggers the sensor to activate the lights. It's an advantage for an occupancy sensor to have more switching zones so it is more sensitive to smaller movements. PIR sensors are not susceptible to false activation or tripping.


For PIR sensors to work best, they need to be installed in open areas with a direct line of sight, such as offices with no partitions, classrooms, factory floors, and meeting rooms. For spaces where the line of sight is obstructed like partitioned offices or irregularly shaped areas, PIR sensors are used in combination with other sensor technologies to make them dual technology occupancy sensors.


Microphonics Technology

Microphonics is a patented advanced detection technology by Sensor Switch, Inc. Microphonics sensors have a microphone inside to hear sounds that indicate occupancy. This is useful in spaces where there are obstructions like offices with cubicles or bathrooms with stalls. Microphonics technology is able to distinguish and isolate human activity sounds from ambient noise and background sounds made by the building or the environment. As such, sounds from cars driving by, air currents, HVAC systems, televisions, and clocks are filtered out to prevent false triggers or keeping the lights on longer. Microphonics sensors also use less power and does not transmit sound waves into a space to eliminate potential interference.


PIR/Microphonics Dual Technology

Combination PIR/microphonics occupancy sensors form a Passive Dual Technology (PDT) for maximum reliability and accuracy. Using PDT, the PIR sensor initially detects motion and activates the light, while the microphonics technology keeps listening for sound to keep the light on as needed. The passive nature of this detection method results in significant energy and cost savings.


Ultrasonic Technology

Ultrasonic sensors detect movement by transmitting high frequency sound waves that are reflected back. The sound waves flood the area of coverage and any moving object that disturbs the pattern will cause the sensor to activate the light, similar to a Doppler Effect. Ultrasonic occupancy sensors produce sound waves that can penetrate partitions, solid walls, and other obstructions. This makes it ideal for busy offices, but also offers a disadvantage by sensing occupancy outside the intended area.


Ultrasonic sensors are also prone to false activations because they cannot distinguish between human and non-human motion. Vibrations, air currents, HVAC systems, and hanging objects might trigger the sensor even if no one is present in the room. The constant high intensity sound waves may also cause interference with office devices.



Sources:

Acuity Brands Lighting

Microphonics vs. Ultrasonic Occupancy Sensors

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