How Does an Ultrasonic Motion Detector Work?

Ultrasonic motion detectors use sound waves to detect disturbances.

Ultrasonic motion detectors can sense disturbances using sound waves. They detect intrusions by monitoring sound waves for the disturbances caused by motion and sound an alarm when disturbances are detected.

Active

Active ultrasonic motion detectors work by emitting a sound wave and monitoring for disturbances in the detection field. Disruptions in the sound wave can set off the alarm depending on how the specific detection unit is calibrated.

Passive

Passive ultrasonic motion detectors "listen" for sounds that fall outside of pre-set parameters. These detectors can be paired with infrared sensors to increase their effectiveness.

Uses

Both types of ultrasonic motion detectors tend to have high rates of false alarms triggered by passing birds or a breeze blowing a curtain. The alarm systems can also be foiled by large pieces of furniture or walls. Areas with high levels of noise from construction or traffic can also make these detectors less effective.

References

• Electronics Information Online: Motion Detector

Resources

• Electronics Information Online: Ultrasonic Sensor