Sep 20, 2026Sensor & Safety Notes
Microwave vs Infrared Motion Sensors for Automatic Doors: Which Do You Need?
Microwave and infrared door sensors solve different problems. Here is how each technology works, where each one wins, and why busy entrances often end up using both together.
Buyers often ask whether a microwave sensor or an infrared sensor is "better" for an automatic door. The honest answer: they do different jobs. Most well-designed entrances end up using microwave for activation, infrared for presence, or a single dual-technology sensor that does both. Understanding the difference makes the choice obvious.
How microwave detection works
A microwave sensor emits a low-power radar signal, commonly at 24.125 GHz, and listens for the Doppler shift reflected from moving objects. When a person walks towards the door, the reflected frequency changes and the sensor switches its relay output to open the door.
Two properties follow from the physics. First, microwave detection only sees movement: a person standing perfectly still in the doorway is effectively invisible to a motion-only microwave sensor. Second, microwave performance is stable across weather: temperature and humidity barely affect it, which is why microwave is the default activation technology for outdoor entrances.
How active infrared detection works
An active infrared sensor projects rows of modulated infrared light (commonly 940 nm) into the doorway region and looks for the reflection. Because it measures a light curtain rather than a moving reflection, it detects stationary bodies as well as moving ones.
Modern infrared presence sensors also perform background self-learning: they memorise the floor and surroundings at power-on and continuously compensate for drift, vibration, sunlight and dirt, correcting themselves so the static background is not mistaken for a person.
Where microwave wins
Microwave is the right activation technology when the task is "open the door for approaching people": retail and supermarket entrances, office lobbies, hospital main doors. It reacts fast, keeps its detection field through bad weather, and works at generous mounting heights. With adjustable detection fields and unidirectional modes, it can also be narrowed so that pedestrians on a busy pavement do not open the door all day.
Where infrared wins
Infrared is the right technology when the task is "do not close on, and do not miss, a person in the doorway": presence detection and safety. It holds detection on a stationary person — someone with a trolley, a wheelchair user waiting in the doorway, a child standing still. It also defines a precise detection zone, which keeps the sensing area inside the door leaf instead of spilling onto the pavement.
The dual-technology middle ground
For many entrances the cleanest solution is one sensor that carries both technologies: microwave motion for opening, an infrared curtain for presence. Dual sensors reduce wiring and header clutter compared with two separate units and are widely used on sliding doors in retail and healthcare.
A quick selection summary
Choose microwave motion when the door only needs to open for approaching movement and the entrance is outdoors or exposed. Choose active infrared when people may stand still inside the door zone. Choose dual-technology when the entrance is busy and public and both jobs must happen in one device. And whatever the technology, confirm the mounting height, detection area and relay output against your door operator before ordering.
Frequently asked questions
Can an infrared sensor open the door too?
Yes — infrared motion-and-presence sensors can trigger activation as well. But on exposed outdoor entrances microwave usually gives a more stable activation field through weather, which is why many designs pair the two.
Do microwave sensors interfere with each other?
Adjacent units of the same frequency can interfere if their fields overlap in the wrong way. Reputable sensors provide channel or frequency options and adjustable fields; a competent installer staggers mounting positions to avoid it.
Which technology is safer?
For people standing in the door zone, active infrared presence detection is the safety technology. Safety is achieved by the presence function, whichever product family provides it.
AURWEN manufactures both microwave activation sensors and active infrared presence sensors, including combined motion-and-presence models for sliding doors. Contact AURWEN with your entrance layout and we will suggest the right technology mix.