What is motion detection?

Motion detection is a feature in security systems that uses sensors to detect movement or activity in a specific area. These sensors, typically placed in strategic locations throughout a home or business, pick up on changes in the environment such as a fluctuation in temperature or a shift in the position of objects can be used to trigger an alarm, send a notification to the user, or both. 

Motion detection can be used as a standalone security feature, or used in conjunction with other measures such as cameras and alarms.

How does it work?

There are several types of motion detectors, including passive infrared (PIR) sensors, microwave sensors, and ultrasonic sensors. 

PIR sensors are the most common type, and work by emitting a field of infrared radiation that detects changes in the ambient temperature within that field. When an object passes through the sensor’s field of view, it causes a change in the ambient temperature, which sends a signal to the security system.

The sensor itself is made up of two parts: a pyroelectric crystal and a pair of infrared detectors. The pyroelectric crystal is responsible for emitting the infrared radiation, while the infrared detectors are responsible for detecting any changes in the ambient temperature.

Microwave sensors, meanwhile, work by emitting a field of microwaves and detecting any changes in the field caused by movement within the sensor’s range. Any disturbance in the microwave field, caused by object movement, is considered a sensor detection. 

Microwave sensors are active, meaning they emit energy themselves in order to function. They’re so highly sensitive and can detect even small movements, however can be disrupted by certain materials such as metal or water, so care must be taken in their placement to ensure optimal performance.

Finally, ultrasonic sensors use high-frequency sound waves to identify movement and are often used in indoor security systems. For these sensors, it’s the shift in sound waves that are considered triggers.

The sensor is made up of an ultrasonic transmitter and an ultrasonic receiver. The transmitter sends out a pulse of ultrasonic sound waves, while the receiver listens for any reflections of the sound waves. When a reflection is detected, the sensor calculates the distance to the reflecting object based on the time it took for the sound wave to return. If the distance changes significantly over a short period of time, it indicates relevant movement. These sensors share the downsides of microwave sensors, in that they can be easily disrupted by particular materials.

What are the downsides to motion detection?

While motion detection is an easily accessible security measure, it has various downsides. These include:

False alarms. Since all sensors can be disturbed by a number of materials, as well as triggered by non-threatening factors including pets, shadows, trees, and changes in temperature, the potential for false alarms is significant. 

Irrelevant alarms can be frustrating and lead to mistrust in the security system, leaving homeowners vulnerable to a genuine threat if they tend to ignore frequent system alerts. They can also be costly if the authorities are repeatedly called to the property needlessly.

Limited range. Motion detectors don’t have an expansive field of view and are only effective at detecting movement within a specific area. This means that they may not be able to detect intruders who enter from other areas, or who cleverly approach the property are outside the view of sensors.

Blind spots. Motion detection sensors may have blind spots where movement is not detected, such as corners, areas with low contrast, bushy areas of the property perimeter and more. This can create significant vulnerabilities in the security system.

Limited capabilities. Perhaps most importantly, motion detection sensors are only able to detect movement and cannot provide other types of useful information, such as what caused the movement and how long the person or object has been on the property. 

Security systems that use more advanced technology offer home and business owners far superior details that can help them prevent intruders before they strike.

While motion detection has historically been used in home and business security, more advanced technologies are coming to the forefront every day, eliminating the many downsides of this almost-outdated security measure.

To ensure the best protection for your property, it’s important to consider all security system options available to you, particularly those that utilise emerging technologies such as artificial intelligence and machine learning.