Electronic devices that use sensors to detect moving objects or people are called motion sensors or motion detectors. A security system would be incomplete without motion sensors. So, how does a motion sensor work? Sensors are designed to trigger an alert when motion is detected, and some systems will send an alert directly to your mobile device. Motion sensors can even be configured to notify your monitoring team if you subscribe to an alarm monitoring service.
Among the most common uses of motion sensors are:
- Detect if an intruder is near or inside your house or business.
- Send you an alert if someone enters a restricted area. An example would be your garage or basement.
- Save energy by turning lights on only when they are needed.
Types Of Motion Sensors
To answer the question how does a motion sensor work, you will need to understand the different types of motion sensors. Active ultrasonic motion sensors and passive infrared motion sensors are the most widely used types of motion sensors. Activated ultrasonic sensors and passive infrared sensors are two of the most common motion sensors, both of which have an excellent reputation for accuracy and reliability.
Active Ultrasonic Motion Sensors
An active ultrasonic sensor emits ultrasonic sound waves that exceed the human hearing range. Motion sensors detect these waves when they bounce off objects in nearby proximity. Sensors contain transducers that act as a waypoint for the signal. They send the pulse and receive the echo. When a sensor sends and receives a signal, it calculates the distance between itself and the target. You can customize the sensitivity for most motion sensors, so they won’t trigger if they’re too far away. Signals received within specified parameters will trigger the motion sensor, alerting you to the presence of someone or something nearby.
Alarms can be configured to activate when motion sensors are installed at entry points such as windows and doors. The sensors on your doors and windows are specifically designed to alert you when an intruder approaches, so you shouldn’t receive a lot of false alarms.
Color, surface, and material type (i.e., metallic versus non-metallic) are not factors that affect the sensitivity of ultrasonic sensors. Often, these sensors are reserved for industrial applications. They can detect translucent objects, as well.
Passive Infrared Motion Sensors
A PIR sensor works the same way as an ultrasonic sensor, but it is more complex. A passive infrared sensor measures fluctuations in infrared energy emitted by humans, animals, and objects.
Everything radiates heat, including walls, floors, stairs, windows, cars, dogs, trees, and people. An infrared camera can detect the temperature of a body. A motion sensor detects a change in temperature of an area when a person or object approaches it.
To demonstrate how this works, let’s look at a motion detection camera, even though it works the same with any PIR motion sensor. A PIR camera has two sensors: one internal and one external. An infrared camera detects ambient IR from doors and walls when no one is present. The first sensor detects the heat signature of a person (or animal, object, etc.) moving past the camera, triggering the camera to turn on, triggering your alarm, and alerting you. The second sensor will detect the sudden drop in temperature when the object leaves the camera’s view.
PIR motion sensors use these temperature changes to determine whether a person or object is present. In the same way that active ultrasonic sensors can ignore small changes in IR, PIR sensors can be set to ignore IR changes during the day or night, making it easier to walk around your home or business without setting off alarms.
Other Motion Sensor Technologies
The following are other less commonly used motion sensor technologies.
Tomographic Motion Sensors
A tomographic motion sensor consists of several nodes. Each node is connected to the others as a mesh network. If a link between two nodes is broken, the sensors detect the presence of people or objects.
Vibration Motion Sensors
Vibration motion sensors detect small vibrations caused by the footsteps of people and objects.
Microwave Motion Sensors
These sensors emit microwave pulses to detect motion. A microwave sensor works similarly to an ultrasonic sensor in that it bounces off objects and returns to the sensor. The sensor’s coverage is greater than that of PIR sensors, but these are more susceptible to interference from electronic sources.
Dual Technology Motion Sensors
Several motion sensors combine two types of sensors in one system, known as dual technology. The goal is to improve detection accuracy by combining active ultrasonic and passive PIR sensors. You can consult your alarm installer for a list of motion sensors that would be most appropriate for your home or business.
Determining How To Maximize Your Sensor Coverage
Sensors can only detect motion in a certain range. Motion sensors typically have a range of approximately 80 feet, so a single sensor may not cover a long hallway or a large open space. Getting your security system installed by a professional and determining where motion sensors should be placed can help you achieve your goals. With fire alarms, burglar alarms, and security cameras, security professionals ensure your home or business is as safe as possible, installing devices and components in the most strategic areas.
Your burglar alarm system will be integrated with the sensors after installing it by a security agent. Your entire security system will be accessible directly from your phone through an app. Make sure you follow the instructions provided with the sensor if you decide to do DIY security.
Tips For Installing Motion Sensors
Here are a few tips for installing motion sensors at your home or business:
- Sensors should be installed near entry points. Specialized motion detectors are available for windows and doors.
- Ensure that they are situated in high-traffic areas. If you place the sensor in a hallway, stairwell, or somewhere people pass through, you’ll likely catch an intruder. Sensors are also a good idea near rooms containing valuable items where burglars may most likely break-in.
- A PIR sensor should not be installed near a heat source. PIR sensors can trigger false alarms if installed too close to vents, furnaces, or fireplaces, which analyze the temperature fluctuations in a given area.
- Make sure the sensor isn’t blocked. Obstruction will prevent the sensors from working. It is not always obvious when an obstruction exists. If, for example, you install a motion sensor light on your home above your driveway, your parked car could block the sensor from detecting motion on the sidewalk. Ensure the sensor is installed in an area free of obstructions.
- To ensure a clear lens, wipe the sensor clean after installation and clean it regularly after that.
Configuring The Sensors Sensitivity Settings
You do not want to get flooded with motion notifications on your phone only to discover that it was just the family pet across the room. Your security professional can adjust the detector’s settings, so it notifies you when something is detected.
If you’re doing a DIY installation, you’ll need to adjust the settings. Please refer to the instructions provided with your motion sensor. A mobile app is most likely included. You can adjust the sensitivity of the app after you download it.
Have you yet to purchase your motion detectors? Take the time to research the settings and features offered by different sensors. Others are full of features that may require hours of configuration, while others are more of a “set-it-and-forget-it” type. Choose the one that fits your needs best.Are you interested in learning about different security solutions you can employ for your safety? Check out the rest of Be-Safe’s resources today!
Daisy is the engine behind Be-Safe.org — from content production to product reviews and more. What drives her is the passion to make home security information easily available.