Which sensors are considered volumetric burglar alarm sensors?

• A. Ultrasonic, Microwave, Passive Infrared (PIR), and combinations of the above
• B. Magnetic contact sensors
• C. Vibration sensors
• D. Acoustic glass-break sensors

Answer: (A)

Volumetric detection focuses on sensing movement anywhere within a space, not just at a single boundary or an isolated event. Ultrasonic and microwave sensors achieve this by emitting waves into the room and detecting changes in the reflected signals when a body moves through the volume. Passive infrared sensors monitor the infrared heat in the area, so a moving warm body alters the detected energy across the room. When these methods are combined, the resulting dual-technology units still detect movement throughout the space, often with improved reliability.

Magnetic contact sensors are point detectors tied to a door or window boundary, so they only trigger when that boundary is opened. Vibration sensors pick up movement through structures, not motion in the surrounding air volume. Acoustic glass-break sensors respond to a specific sound event, not ongoing movement through the space.

So the sensors that are considered volumetric burglar alarm sensors are ultrasonic, microwave, PIR, and combinations of the above.