What are Microwave Motion Sensors?

Microwave motion sensors are motion detecting sensors that use microwave radar technology to detect the presence of motion. These microwave sensors will typically also use a secondary method for detecting motion, such as PIR sensing, to more accurately detect motion and prevent false alarms.

A motion sensor that uses microwave technology will be constantly sending out microwave signals. The signals will bounce off any objects in the area and return to the sensor. As long as no motion is present, the signals will maintain a consistent pattern, and the sensor will assume that everything is alright. Any significant movement will cause the return pattern of the microwave signals to change. If this happens, the microwave sensor will recognize that motion is present in the area.

However, microwave technology cannot be trusted to accurately detect motion on its own. Microwave signals are able to pass through solid objects. As a result, microwave sensors can sense motion that occurs on the outside of a building. If a sensor only used microwave detection, then it would be very likely that many false alarms would happen because of movement that occurs on the outside. This would lead to many undesirable results. That is why standalone microwave sensors cannot be trusted.

For that reason, nearly every microwave motion detector is paired with a second motion sensing technology. This is most commonly passive infrared (PIR) technology. When a motion sensor uses both microwave radar and PIR technology, it is referred to as a dual-tech sensor. For these devices, both the microwave sensor and the PIR sensor must be activated in order to an alarm to occur. This makes false alarms much less likely to happen, since it is highly unlikely that both sensors would be activated accidentally. But both sensors should still respond reliably when real motion is present.