What Is a Dual Action Motion Sensor?

A dual action motion sensor is a motion detection sensor that uses both passive infrared (PIR) technology and microwave detection technology. For a dual tech motion sensor, both the PIR sensor and the microwave sensor must be triggered for the sensor to activate and alert the system.

Most motion sensors utilize PIR technology as their sole detection method. These are relatively simple devices. If the PIR sensor is triggered, then the sensor will alert the security system. But PIR sensors aren't perfect, and a device might be triggered due to something like light, flowing air or a ceiling fan. This is usually the result of poorly mounting the sensor, and most users do not experience this issue. But it is something to think about when using a standalone PIR motion detection sensor.

A dual tech motion sensor adds microwave detection technology to the sensor. For these sensors, both the PIR sensor and the microwave sensor must be activated. The sensor won't activate if just the PIR sensor or just the microwave sensor activates. So even if an external source causes the accidental activation of one sensor, it will be okay because the other sensor will remain undisturbed. This will go a long way towards preventing false alarms.

It's important to understand how both PIR sensors and microwave sensors work. PIR sensors look for changes in infrared energy that occur with movement. Every person and object gives off some infrared energy that the sensor detects. A large disturbance in infrared energy will activate the PIR sensor. Many motion sensors are equipped with special technology that helps to confirm that the energy signature matches that of a human. But these sensors are not always perfect.

As for microwave detection technology, the technique is relatively simple. The motion sensor will use a process known as the Doppler effective. The microwave sensor will send out continuous microwave signals and take note of how they bounce off of objects and return to the sensor. If a new person or object comes within the sensor's field of view, it will change the pattern of the microwave signals. If the change is large enough, the microwave sensor will activate.

What's crucial to understand about microwave signals is that they pass through walls and other barriers. In other words, a microwave sensor can theoretically detect movement that occurs outside the home. For that reason, a standalone microwave sensor is not a suitable device. It would cause too many false alarms. The microwave technology must be paired with the PIR technology to prevent constant false alarms.

With a dual tech or dual action motion sensor, the PIR technology keeps the microwave technology in check, and vice-versa. Even if something like flowing air or sunlight activated the PIR sensor, these sources would not activate the microwave sensor. Likewise, even if the microwave sensor responds to something outside the home, that source would not affect the PIR sensor. Only true movement inside the building will activate both the PIR sensor and the microwave sensor. This makes dual tech motions a great option for users who want to eliminate the possibility of false alarms, while still receiving reliable motion detection.