Movement Sensors: How do they work?

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PIR vs Microwave Movement Sensors… What’s the difference?

Passive Infrared (PIR) and Microwave movement sensors differ in the way that they detect movement, and are better suited to different environments. Both are fantastic technologies, but there are a few things you should consider when choosing one over the other.

Passive Infrared (PIR) Movement Sensors

PIR movement sensors use an infrared light sensor to detect the movement of people or objects. They pick up on the heat signature of warm bodies, such as humans or animals that are warmer than their surroundings.

PIR sensors are good at detecting ‘big’ movements of heat such as a person or vehicle moving through their field of view. They are less likely to pick up on changes in the heat signature caused by small movements such as moving trees or warm wind, so they are less prone to nuisance triggering. This makes them a great choice for outdoor use.

PIR sensors are the most commonly used type of sensor, and they are used in a variety of environments:

Clipsal PIR Movement Sensor
Movement sensors installed alongside security lighting to detect intruders
HUNTER III LED 2 Light Floodlight with Sensor
Movement Sensor integrated with external security lighting
  • Installed with internal lights in pantries, hallways or bathrooms to activate lighting and fans
Clipsal Indoor Movement Sensor
Indoor movement sensors work well in pantries or walk-in robes
  • ‘Pet-friendly’ versions that don’t detect smaller heat signatures can be installed in homes to allow security alarms to be activated even when your pet is inside

Proper positioning is vital for PIR sensors to function correctly. They are very effective when installed overlooking pathways, driveways or other defined areas that people or vehicles will move through. It's also helpful to know that PIR sensors do not detect movement through walls or windows.

If a PIR sensor is installed near a hot air vent or in direct sunlight, the warm air can prevent the sensor from properly detecting movement. So it’s important that movement sensors are positioned in locations that allow them to operate effectively.

 

Microwave Movement Sensors

Microwave movement sensors emit microwaves at consistent intervals, and when movement occurs in its field of view, the distortions in the microwaves returning to the sensor cause the sensor to trigger.

This means that microwave sensors are a lot better at detecting very small movements which makes them ideal for indoor use as ‘occupancy sensors’, when you need to detect smaller movements by humans.

Microwave sensors are the best option to use in the following scenarios;

  • Installed in public bathrooms to detect small movements of people in stalls (avoid that awkward waving to re-activate the lights)
  • Installed in offices and boardrooms where people sit relatively still for long periods of time
  • Installed in areas that may be affected by direct sunlight or hot air vents (where PIR sensors are not effective)
  • Installed in wide open indoor spaces that need 360 degree coverage
EYE 360 Microwave Security Sensor
360 degree microwave sensor for wide indoor spaces

This type of sensor can detect movement through non-metallic materials, such as wood, glass and even brick! Because it can ‘see’ through solid objects, microwave sensors can be integrated into light fittings to detect when someone enters a room (so the sensor is hidden)!

 

ACCORD LED Flush Ceiling Light with Microwave Sensor
Microwave sensor integrated into a light fitting

Interested in getting movement sensors installed at your home or business?

Kenner Electrics recommends and installs high quality Clipsal Infrascan movement sensors, which are reliable and long-range and great as a general purpose movement sensor. We also have other products which we will recommend depending on your unique situation. Our expert electricians will make sure your lights and sensors are positioned correctly to provide maximum coverage.

Visit our website to see how we can help.