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How Do Motion Sensors Work?

March 30, 2023

What Are Commercial Motion Sensors?

Commercial motion sensors are electronic devices that detect movement. They come in a variety of forms and are central to most building management automations and security installations. Motion detection technology designed for camera systems improves video storage efficiency, while motion sensors designed for burglar alarms trigger alerts and deterrence tools when unauthorized movement is detected.

Commercial motion detectors are also used for building automations like automated lighting and HVAC management to improve convenience and energy efficiency.

How Motion Sensors Work

Most motion detectors work by detecting changes in infrared radiation, sound waves, microwaves, magnetic fields, or other patterns within their monitoring range. As soon as motion is detected, the sensor sends an electronic signal to a connected device or system, which then activates a desired function, such as turning on a light or initiating an alarm.

Types of Motion Sensors

Passive Infrared (PIR) Sensors

Passive infrared sensors detect changes in infrared radiation emitted by living beings. They're the most commonly used motion sensor type, called "passive," because they don't emit frequencies into the atmosphere.

Ultrasonic Sensors

Ultrasonic sensors emit high-frequency ultrasonic waves that bounce off objects. They detect objects' movement when the wave patterns they create are disrupted.

Microwave Sensors

Microwave sensors emit low-power microwave pulses and detect intruders by recognizing changes in microwave patterns.

Tomographic Sensors

Tomographic sensors use multiple sensors to emit radiation and create 3D images. These sensors are most commonly used in airport security to scan luggage and penetrate clothing to identify concealed threats.

Vibration Motion Sensors

Vibration motion sensors, also known as seismic sensors, use highly sensitive components, such as piezoelectric crystals and accelerometers, to detect the small vibrations that occur when objects move.

In security applications, vibration sensors help to detect attempts to break into buildings or tamper with security equipment. They can also be used to detect earthquakes and monitor machinery for signs of failure or wear.

Area Reflective Sensors

Area reflective sensors emit beams of light that are reflected back by nearby objects. These sensors are often used in automatic doors, as well as in warehouse and factory environments, to protect high-value inventory.

Dual Technology Motion Sensors

Dual technology sensors combine two different sensing technologies, such as passive infrared sensors and active ultrasonic sensors, to reduce the likelihood of false alarms.

Where to Put Motion Sensors

Motion detector

Commercial motion-sensing devices are commonly installed on ceilings, walls, around entrances, and within light fixtures.

Security Systems

Motion sensors are crucial to most security systems, especially for intrusion detection. Once installed, they can be set to monitor areas when they should be free of movement, such as office spaces after the last authorized employee locks up.


Instead of continuously recording all footage from live feeds (and rapidly filling up storage space), many cameras contain motion sensors so that footage isn't stored unless movement occurs in the camera's field of view.

Doors and Windows

Motion sensors are installed in doors and windows to detect attempted entries and break-ins. These motion detectors are installed across from magnets in window frames. When the window is opened, the magnetic field breaks, and the alarm initiates.

Burglar alarm window sensor.

Motion sensors for doors similarly use sensors and magnets to recognize unauthorized openings.


Motion sensors can be embedded inside light fixtures to detect movement. These embedded sensors can be used either to recognize unauthorized movement or to improve a building's energy efficiency and convenience. For example, motion-sensing lights can turn on or off depending on movement and can adjust their brightness depending on the availability of natural light.

Advantages of Motion Sensors

Security and Intrusion Prevention

Motion sensors in intrusion alarms detect unauthorized movement. They can be programmed to provide alerts to relevant users, remote monitoring services, or law enforcement. They work most effectively when connected to commercial security cameras and deterrence tools like sirens and strobe lights.

Deterrence tools usually work, but when they aren't enough, alarm systems integrated with security cameras are able to present relevant footage alongside alarm notifications. Such integrations make it easy to disable false alarms quickly, but most importantly, they enable eyewitness accounts of genuine intrusions that usually result in speedy, priority police dispatches.

Surveillance Efficiency

Not only do smart motion sensors in cameras preserve high-value video storage space, but they also make investigations easier by avoiding hours of unnecessary footage.

Improved Energy Efficiency

Motion sensors are used for more than just security. When integrated with building management systems, they can automatically turn lights on or off and adjust temperature settings to save energy and lower utility bills.

Enhanced Operations

Some commercial motion sensors, known as occupancy sensors, collect data about building usage and occupancy patterns. This information is used to make better use of site resources and automate actions for optimized workflows. For example, motion sensors in a warehouse can be programmed to automatically open necessary doors when approaching forklifts are detected.

Dynamic Product Lighting

Motion sensors can improve retail sales by lighting up particular items as people approach. Not only does dynamic lighting improve energy efficiency, but it also draws attention to specific items much more effectively than standard lighting systems.

Automatic Customer Doors

Automatic customer door sensors work by using ultrasonic sound waves or microwaves to detect approaching customers.

Motion sensor at electronic customer door.

These sensors are especially helpful for people with disabilities, those carrying heavy items, and the prevention of injuries caused by caught fingers and people on the wrong side of manual doors.

Disadvantages of Motion Sensors

Limited Range

One disadvantage of motion sensors is a limited detection range that may leave blind spots for intruders to exploit. Product spec sheets should be reviewed to select the right sensor to monitor a given area. A sensor used outside of its optimal range can have serious consequences for critical security systems.

False Alarms

Pets, swaying trees, and other environmental factors can trigger some sensors to cause false alarms that frustrate managers, reduce the likelihood of an adequate response during a real emergency (the "boy who cried wolf" effect), and sometimes result in punitive fines from local authorities.

One common cause of false alarms occurs during installation when sensors are placed too close to heating vents, furnaces, fireplaces, and other heat sources. When too close to heat or improperly angled, motion detectors can mistake the movement of hot air for actual motion.

That said, there are times when it is necessary to place motion sensors near heat sources. Experienced installation experts, such as our team at Mammoth Security, are familiar with tools and methods to reduce the likelihood of false alarms in such situations.

For example, some motion detectors feature built-in temperature sensors to differentiate between heat and actual motion. A heat shield or other insulation around a sensor is also a viable option for certain motion sensor types.

Blocked Sensor Signals

Some motion sensors are unable to detect motion when blocked by furniture, decorations, and other objects. Blocked sensors result in security gaps that can be exploited by intruders.

Radiation Concerns

Microwave sensors emit safe levels of electromagnetic radiation, levels similar to those emitted by cell phones and Wi-Fi routers.

Tomographic sensors, on the other hand, emit high-energy forms of radiation that can potentially damage living tissue. Fortunately, these sensors are rarely used outside of airport security gates and medical rooms.

If you have concerns about potential health effects from radiation emitted by motion detectors, consult with the friendly security experts on our team here at Mammoth Security. Our crew can help you select security devices that use radiation-free motion sensor technology.

What You Should Know When Choosing Motion Detectors

Security System Integration

Make sure the motion detectors you use are compatible with the rest of your security installation. By consulting with installation experts on our team at Mammoth Security, you can make sure that your sensors will integrate with your other security components, such as control panels, cameras, and, of course, alarms.

Sensors work best when integrated with other sensors and security devices like video surveillance cameras.

By selecting ONVIF-compliant cameras, open-source software systems, and modular motion detectors, you can have a security installation that is effective, reliable, and easy to customize and scale now and into the future.

Level of Sensitivity

Most motion sensors allow users to fine-tune sensitivity levels for their specific needs to ensure that sensors will trigger when needed or to prevent false alarms. For example, a pet-friendly security system will include sensors that can be programmed to ignore movement by small animals.

Sensor Type

Different types of motion sensors are designed to meet specific security conditions and building management needs. Depending on your requirements, one or more alarm system sensor types may be used in combination for maximum protection with the fewest false alarms.

Protect Your Business With Motion Sensors Installed by Mammoth Security

Mammoth Security knows how cameras, access control devices, and burglar alarms work.

There are many different types of motion sensors, all with unique functionalities to consider when developing your security system. What's more, limited ranges, false alarms, and blockages caused by small oversights can all degrade their effectiveness.

There's a lot to sort through, but our crew at Mammoth Security knows how to place, calibrate, and combine sensors for maximum effectiveness with the fewest false alarms.

To learn more about the right sensors and security components to protect your property, schedule a free, zero-obligation consultation with a friendly expert on our team. Just fill out the simple form below, and we'll quickly reach out to schedule your free site survey and security assessment.




The most common type of motion detector for businesses are passive infrared (PIR) motion detectors. They detect infrared radiation emitted by moving objects and are popular tools both for security enhancement and energy efficiency.

Motion sensors and Wi-Fi usually coexist without conflict because they operate on different frequency bands. That said, some motion sensors use Wi-Fi or Bluetooth signals to communicate with other devices in an integrated security installation, which can potentially result in interference.

Most motion sensors work without Wi-Fi or any Internet connection at all. Instead, they use technologies like infrared, ultrasonic, or microwave signals to detect motion.

Some motion sensors do use Wi-Fi to communicate wirelessly with other security devices, but commercial-grade security should be hardwired whenever possible to avoid the unreliability inherent to Wi-Fi.

Occupancy sensors are often installed in high-traffic areas, such as retail stores or transportation hubs, to count the number of people passing through. This information can be used to optimize staffing levels, improve workflows, and enhance the overall customer experience.

A PIR motion sensor can be tripped by any object that emits heat. Infrared sensors detect changes in infrared radiation, which is emitted by all objects that have a temperature above absolute zero. As a result, anything that emits heat can potentially trip a PIR sensor, including people, animals, cars, and even moving air currents.

That said, professional installers, like those on our team at Mammoth Security, know how to install and configure PIR sensors to ignore small objects, heat movement, and other common causes of false alarms.



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