Both businesses and employees alike are keen on coming back to the office in some form or another, but doing so requires strategic planning. Most companies are still learning about what role their office will play in the daily lives of their employees, so many are looking for data that can help them do just that. Many of this data is coming from occupancy sensors. Granted, occupancy sensors existed way before the pandemic, but now they top the minds of building managers and occupants who want to do everything they can to understand the new, changing work landscape.
Historically, buildings relied on their access control systems to help them understand how many people were in the building. This might indicate how many people are in an office, but does not help connect the dots for how people are actually using the space once inside. Occupancy monitoring sensors are becoming an increasingly important tool to understand how (and how much) a space is being used. Using them effectively can enable a building manager to identify which spaces are under-used so that they’re not wasting energy on lighting, heating, or air conditioning in empty rooms. But each type of sensor has its limitations and none of it, of course, works without robust analysis of the data that they create.
Let’s take a closer look at the types of occupancy sensors:
Ultrasonic sensors emit high-frequency sound waves into a space in order to detect a reflected pattern. The sound waves are broadcast at a frequency of around 40kHz, which is beyond the capacity of human hearing (humans can only identify sounds between 20 Hz or 20kHz). Ultrasonic sensors recognize the room’s constant condition, so it detects movement when there is a change in that frequency.
Ultrasonic sensors are great for offices as they do not rely on line-of-sight sensing, so they can operate in the dark, and are more successful in sensing motion around corners and in cubicles. They’re especially well-suited to situations where there’s only a tiny amount of movement.
They do have their downsides, though, which includes a limited sensing distance and sensitivity to temperature changes. Plus, the accuracy of these sensors fluctuate depending on the temperature of the room. The speed of an ultrasonic sensor’s waves is affected by changes as little as 5 degrees Fahrenheit.
A Bluetooth beacon is a device that transmits a continuous radio signal that smart devices, like smartphones or bluetooth tags, can detect once that other beacon is in range. The devices swap their unique ID numbers to alert each other exactly which beacon (i.e. which person) is nearby.
The entire beacon ecosystem relies on Bluetooth for its infrastructure. Bluetooth beacons can be placed around a space and used to triangulate where each connected device moved within the network. However, the downsides are that this usually has to be done via an app on each occupant’s mobile phone, which can be difficult if not impossible in many large offices.
Thermal sensors and more specifically, Passive Infrared (PIR) sensors detect the heat emitted from the human body. These sensors pick up thermal signals from their surroundings and can detect when they are disrupted by the presence of a human. PIR sensors exist in a variety of shapes and sizes, with some mounted on walls or ceilings and others hidden behind desks. They’re usually unobtrusive, simple to install, and low-maintenance.
However, if the employee or tenant sits relatively still, PIRs may not be able to detect movement. PIRs typically time out as a result of this, forcing the tenant to wave a hand or make another type of dynamic movement to re-activate the lighting system.
Acoustic sensors detect human-made noise as well as mechanical noise associated with human activities, such as typing, moving papers, photocopying, and so on. However, few occupancy sensors solely rely on acoustic detection.
Acoustic sensors can also respond to sounds unrelated to the space’s occupants, such as slammed doors and traffic noise, making them an imprecise tool for occupant detection on their own. They also require high sound levels to activate, higher than those found in a typical quiet office. That’s why many acoustic sensors are combined with PIR technology in order to be a more reliable option for building owners.
These work in a similar way to ultrasonic sensors, in that they send high-frequency microwaves into an area and look for a reflected pattern. When a moving object enters the detecting field, the reflections alter. Microwave sensors are more sensitive than other sensors– for instance, microwaves can actually penetrate most building materials– and have a wider detection range. Plus, microwave sensors aren’t nearly as temperature sensitive as ultrasonic sensors.
However, like PIR sensors, microwave sensors often result in false readings. If a building manager opts for a microwave sensor, it’s critical that their levels are set correctly when they’re installed.
People recognition cameras
People recognition cameras can recognize the shapes of people’s faces or bodies to estimate the number of individuals in a room, providing a more precise picture of the utilization of a room or a specific region than PIR sensors. Some companies prefer using these cameras to count occupancy. But, these cameras can be costly, not to mention controversial when it comes to privacy concerns. The growing surveillance of people has privacy advocates pushing firms to limit using people recognition cameras.
“The question becomes whether the tech remains after the public health problem goes away, and that is the real privacy fear,” said Al Gidari, a privacy expert at Stanford Law School. “Video in the store today to ensure social distancing remains to identify shoplifters tomorrow.” Furthermore, cameras may cause apprehension in many people, whether at home, on the street, or at work. Regardless of their declared purpose, lenses tend to indicate a lack of trust, and trust is one of the most critical parts of any organizational setting, according to workplace culture experts.
Infrared motion sensors
Not to be confused with thermal PIR sensors, infrared beam motion sensors are another type of sensor that uses infrared technology. They emit a laser beam that can detect when someone or something moves in front of it. You may not be able to see the light as you pass it since it becomes fainter as you get further away from it.
These sensors measure the temperature radiated by a person as they move closer or further away from the sensor, allowing you to measure static or moving persons. The field of view expands as the distance from the sensor rises, but the angular size appears smaller. The sensor can detect accurate temperature and shape when the distance between the sensor and the object narrows. Because no photos or personal information are saved or transferred, these sensors are GDPR and privacy-compliant.