Editorial Feature

How Does an Occupancy Sensor Work?

AZoSensors defines the working principle of occupancy sensors, their applications to industry and the current commercial landscape.

A Guide to Occupancy Sensors

Image Credit: Andrii Yalanskyi/Shutterstock.com

What are Occupancy Sensors?

Unlike motion sensors, occupancy sensors can detect the presence of a person even when they are not in motion. They can control lights, such that they can switch on the light when detecting a person walking in the room and keep the light on until they leave. Furthermore, occupancy sensors have also been integrated to exhaust fans in public restrooms, which turn the fan on when the bathroom is occupied and automatically switch it off when the occupant leaves.

Occupancy sensors have been largely used in commercial buildings and residential complexes. Here, these sensors enable automated lighting and ventilation systems like fans and Heating, Ventilation, and Air Conditioning (HAVC) to significantly reduce energy wastage. 

A complete building occupancy monitoring solution provides data on every important space in a building, i.e., desks, rooms, and open areas of buildings. These real-time occupancy data helps an individual know whether a space is occupied and how it is being used. Occupancy sensors can also help detect underutilized spaces, i.e., whether a meeting room will accommodate all people scheduled to attend the meeting. 

Different Types of Occupancy Sensors

Typically, occupancy sensors detect motion or any changes in the environment using various sensing technologies. For instance, it uses passive infrared (PIR) technology to detect motion or any other changes in its field of view. A PIR occupancy sensor can provide data on space occupancy.

PIR occupancy sensors use two pyroelectric sensors that are sensitive to IR signals to detect IR radiation in the environment. In the case of no motion, the sensor detect the same amount of IR in both pyroelectric sensors. However, in the presence of a warm body, such as a human or pet walking within the range of the detecting space, the PIR occupancy sensors first intercept one slot and then the other.

Subsequently, it generates a positive differential change between the two slots, which indicates motion. Similarly, when a person leaves the room, a signal change determines whether the room is unoccupied. PIR occupancy sensors are more sensitive to lateral motion but less to axial motion.

High-frequency sound waves are emitted by ultrasonic occupancy sensors beyond the human hearing range. It uses the Doppler effect of returning sound waves to recognize human presence. Infrared (IR) occupancy sensors are similar to ultrasonic-based devices. However, instead of sound, they use IR light.

Ultrasonic occupancy sensors have in-built transducers consisting of a transmitter and a receiver. When a soundwave is sent from the transmitter, it bounces off objects in the area and reflects back to the receiver. The change in the frequency of the reflected sound waves is interpreted as a motion.

The sensor can determine the distance between the sensor and the target based on the time between sending and receiving the sound wave. These ultrasonic sensors are ideal for places with obstacles in the path, for example, public restrooms with many stalls. 

In the case of microwave occupancy sensors, low-power electromagnetic radiation is transmitted and received, and the change in the radiation indicates motion. Since microwaves can penetrate walls and holes, they have more extensive coverage. Hence, microwave occupancy sensors are extremely adaptable and can be applied in any environment.

Dual-technology occupancy sensors are a combination of PIR and ultrasonic sensors for motion detection. This combination has significantly enhanced the sensitivity and overall performance of the sensor. This type of sensor also uses the Internet of Things (IoT) to share data over the internet.

Application of Occupancy Sensors

Occupancy sensors are strategically placed such that they can easily detect motions in high-traffic and isolated areas. Notably, these sensors are designed to be discreet, i.e., they can be installed in the ceiling to monitor individuals or groups entering or leaving a zone, floor, buildings, or rooms. For instance, the most commonly used PIR occupancy sensor is a desk sensor, which is placed on the underside of the desk and informs about desk occupancy.

The data collected by this electronic device is transferred to a cloud-based platform where AI algorithms estimate real-time space utilization and occupancy levels. These data can also be integrated with other systems, such as HVAC, lighting, and booking systems, as soon as predetermined levels are reached.

The type of occupancy sensors implemented depends on the need of the user. For instance, a user’s requirement could be to assess space utilization, improve energy efficiency, or manage meeting room sizes. For instance, PIR occupancy sensors can indicate whether a zone is occupied or not. However, this sensor cannot tell the number of occupancies and is aligned for facilitating desk hoteling.

Bathroom occupancy sensors provide an anonymous insight into washroom usage. The facilities management team can use this sensor to deploy cleaning staff after a predetermined amount of usage by visitors is reached. This occupancy sensor provides automatic notifications, such that these facilities get properly attended and the user’s health and hygiene are properly taken care of. Furthermore, effective management of washrooms decreases maintenance costs substantially. 

Commercial Landscape of Occupancy Sensors

The available occupancy sensors come with different data and integration capabilities, efficiency, and accuracy levels. Therefore, it is imperative to choose the correct sensor according to the need. 

The global occupancy sensors market is highly competitive and some of the key players include Schneider Electric, Eaton Corporation, Acuity Brands, Honeywell International, Legrand, General Electric, Pammvi Group, and Leviton. 

Continue reading: Zone Ventilation Control in Buildings

References and Future Reading

Bell, T. (2023) The Guide to Occupancy Sensors. [Online] Irisys (InfraRed Integrated Systems Ltd). Available at: https://www.irisys.net/resources/guide-to-occupancy-sensors

He, H. (2022) Occupancy Sensors: The Definitive Guide. [Online] Rayzeek. Available at: https://www.rayzeek.com/blog/everything-about-occupancy-and-vacancy-sensors

Dubey, N. (2022) Top 6 Motion Sensor Manufacturers in the World. [Online] BISinfotech. Available at: https://www.bisinfotech.com/top-6-motion-sensor-manufacturers-in-the-world/

Technavio Announces Top Nine Prominent Vendors in the Global Occupancy Sensor Market from 2016 to 2020. [Online] Businesswire. Available at: https://www.businesswire.com/news/home/20160518005037/en/Technavio-Announces-Top-Nine-Prominent-Vendors-in-the-Global-Occupancy-Sensor-Market-from-2016-to-2020

Guo, X. et al. (2010) The performance of occupancy-based lighting control systems: A review. Lighting Research and Technology. 42(1). https://journals.sagepub.com/doi/10.1177/1477153510376225

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Dr. Priyom Bose

Written by

Dr. Priyom Bose

Priyom holds a Ph.D. in Plant Biology and Biotechnology from the University of Madras, India. She is an active researcher and an experienced science writer. Priyom has also co-authored several original research articles that have been published in reputed peer-reviewed journals. She is also an avid reader and an amateur photographer.

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