7 presence sensors that buildings use to track return to work

Both companies and employees want to get back to the office in some form, but doing so requires strategic planning. Most companies are still learning the role their office will play in their employees’ daily lives. Hence, many are looking for data that can help them do this. Much of this data comes from presence detectors. Granted, occupancy sensors were around long before the pandemic, but now they’re ruling the minds of building managers and residents who want to do whatever it takes to understand the new, changing work landscape.

In the past, buildings relied on their access control systems to understand how many people were in the building. This can indicate how many people are in an office but does not help connect the dots for actual use of the space inside. Presence monitoring sensors are becoming an increasingly important tool for understanding how (and how much) a room is being used. By using them effectively, a facility manager can identify which rooms are underutilized so that he does not waste energy on lighting, heating or air conditioning in empty rooms. But every type of sensor has its limitations and of course none works without a robust analysis of the data they generate.

Let’s take a closer look at the types of presence detectors:

Ultrasonic sensors

Ultrasonic sensors send high-frequency sound waves into a room to detect a reflected pattern. The sound waves are emitted at a frequency of around 40 kHz, which is beyond the human ear (humans can only recognize sounds between 20 Hz or 20 kHz). Ultrasonic sensors recognize the constant state of the room and detect movements when this frequency changes.

Ultrasonic sensors are great for offices because they don’t rely on line-of-sight detection, so they can work in the dark and better detect movement around corners and in cubicles. They are especially good for situations where there is little movement.

However, they have their drawbacks, including limited range and sensitivity to temperature changes. In addition, the accuracy of these sensors varies depending on the room temperature. The speed of the waves from an ultrasonic sensor is affected by changes of only 5 degrees Fahrenheit.

Bluetooth beacons

A Bluetooth beacon is a device that sends a continuous radio signal that smart devices such as smartphones or Bluetooth tags can detect as soon as another beacon is within range. The devices exchange their unique ID numbers to notify each other of exactly which beacon (i.e., which person) is nearby.

The entire beacon ecosystem depends on Bluetooth for its infrastructure. Bluetooth beacons can be placed around a room and used to triangulate where each connected device is moving within the network. The downside, however, is that this usually has to be done via an app on each resident’s cell phone, which can be difficult if not impossible in many large offices.

Thermal sensors

Heat sensors and especially passive infrared sensors (PIR) recognize the heat given off by the human body. These sensors pick up thermal signals from their surroundings and can detect when they are disturbed by the presence of a person. PIR sensors come in a variety of shapes and sizes, with some mounted on walls or ceilings and others hidden behind desks. They are usually inconspicuous, easy to install and require little maintenance.

However, if the employee or tenant is sitting relatively still, PIRs may not be able to detect movement. This usually results in PIRs timing out, forcing the renter to wave a hand or make some other type of dynamic movement to reactivate the lighting system.

Acoustic sensors

Acoustic sensors detect both man-made sounds and mechanical sounds associated with human activities such as typing, moving paper, photocopying, etc. However, only a few presence detectors rely exclusively on acoustic detection.

Acoustic sensors can also respond to noises unrelated to room occupants, such as doors slammed and traffic noise, making them an inaccurate tool for occupant detection. They also require high noise levels to activate, higher than in a typical quiet office. For this reason, many acoustic sensors are being combined with PIR technology to be a more reliable option for building owners.

Microwave sensors

These work similarly 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 detection field, the reflections change. Microwave sensors are more sensitive than other sensors – for example, microwaves can penetrate most building materials – and have a larger detection area. In addition, microwave sensors are nowhere near as sensitive to temperature as ultrasonic sensors.

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However, like PIR sensors, microwave sensors often produce incorrect readings. If a building manager chooses a microwave sensor, it is important that their levels are set correctly when they are installed.

Person recognition cameras

People detection cameras can detect the shapes of people’s faces or bodies to estimate the number of people in a room, and provide a more accurate picture of the use of a room or a specific region than PIR sensors. Some companies prefer to use these cameras to count occupancy. However, these cameras can be expensive, not to mention controversial when it comes to privacy concerns. The increasing surveillance of people has resulted in data protection officers pushing companies to restrict the use of cameras for person identification.

“The question is will the technology last after the public health problem goes away, and that is the real fear of privacy,” said Al Gidari, privacy expert at Stanford Law School. “A video in the store today to ensure social distancing is maintained to help identify shoplifters tomorrow.” Additionally, cameras can be a concern for many people, be it at home, on the street, or at work. Regardless of their stated purpose, lenses tend to indicate a lack of trust, and trust is one of the most critical components of any business environment, according to workplace culture experts.

Infrared motion sensors

Not to be confused with thermal PIR sensors, infrared motion sensors are another type of sensor that use infrared technology. They send out a laser beam that can detect when someone or something in front of them is moving. You may not be able to see the light as you walk past it as it weakens the further you go from it.

These sensors measure the temperature emitted by a person as they approach or move away from the sensor, so you can measure people who are still or moving. The field of view widens as the distance from the sensor increases, but the angular size appears smaller. The sensor can know the exact temperature and shape when the distance between the sensor and the object becomes smaller. Since no photos or personal information are stored or transmitted, these sensors are GDPR and data protection compliant.

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