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What is the difference between a presence and motion sensor?

group of workers in laid-back office environment

The little but important differences…Also, what is actually an occupancy sensor?

Not only system integrators but also home owners are often wondering – What is the difference between a detector for presence, movement and occupancy? Unfortunately, both terms are often used in the non-correct manner, which is why this article would like to explain you the major differences between sensors for “Motion” and “Presence”.

Both sensors come from the same family of devices. However, due to (or rather thanks to) the technical evolution, both kinds of sensors started to develop in separate ways, creating two new ways of creating telegrams and sending them on the bus. Therefore, it is of most importance to understand the difference:

Motion Sensors: Detecting walking movements

The motion detectors perceive walking movements in the selected detection zone and respond to them accordingly: The Light is switched ‘ON’ when a movement is detected once ambient light levels fall below a preselected threshold. After a set period, the light switches ‘OFF’ again.

The recommended uses of motion sensors include the detecting of moving objects outdoors or in busy indoor areas, such as hallways or corridors.

Due to their lower price, resulting from the lower sensitivity, motion sensors are used more often, compared to other detectors, thereby being more likely to be found in new and existing installations.

Presence Sensors: Detecting tiniest movements

Compared to a motion sensor, which would detect the movement of an arm, the presence sensor would detect the movement of a finger. Using extremely high resolution, precision and sensor technology, they respond to the tiniest movements.

The high fidelity is especially required in sedentary areas, such as offices and classroom, at which the no big movements can take place for a longer period of time, but lighting is still required. Also, presence sensors have the possibility to overcome longer distances, meaning that they can easily be placed at high ceilings, such as in sports halls and warehouses, and still be able to detect movement on the ground. Due to the fact that they detect the smallest movements, presence sensors are also referred to as occupancy sensors.

Basalte Auro and Theben the Piccola sensors next to each otherImage: www.ivoryegg.com

Both sensors have a very important feature in common: Energy Efficiency

Depending on your need and your requirements, the choice between a motion sensor and a presence sensor can now be made easier with this information. What is however totally not influenced by your choice is the fact that both kind of sensors realise a higher energy efficiency for lighting, but also other applications.

As the switching does not have to be done by human interaction, the light will only be switched on, when the room is occupied, respectively, when moving is going on. By not having to worry about forgotten lights, energy is automatically used more efficiently.

office space with chairs and desks featuring knx sensors

Check out some of the projects in which both sensors have had a huge impact at http://projects.knx.org

This article originally featured on the KNX blog.


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