|
Definition
Ultrasonic transducers can be used to detect motion in an area where there are not supposed to be any moving objects.
Working
The ultrasonic detector transmits continuous high frequency whistle that human hearing frequency is incapable of detecting. This high frequency whistle gets reflected from all surfaces and reaches receiver of ultrasonic detectors in the transmitted form provided all the objects continue to remain in their original position. Now in case, if the transmitted frequency gets altered during its course of path, a change is introduced in the transmitted frequency. This is called the doppler effect. This change occurs due to displacement of the objects from their original position. The change in the frequency of the transmitted frequency triggers alarm by the Ultrasonic detectors. In order to ensure that false alarms cannot be caused by turbulence in the air or the movement of curtains or the like, measures are taken in the detector design. Advanced ultrasonic units are provided with an anti-masking feature which prevents any obstruction being placed before the unit. In these cases it will signal an alarm condition if anything is too close. This also ensures that a mask cannot be placed over the face of the detector.
Unfortunately some installers attempt to standardize on their use of detector rather than viewing each application independently. There are many instances where the ultrasonic principle is the best option.
The ultrasonic detector does not have its sensitivity impaired by the ambient temperature and it detects an approaching body more effectively than a PIR. Also it readily neglects pulsating heat sources which can prove troublesome for an infra red detector.
Advantage
The main advantage of ultra detectors is that they are very sensitive and extremely fast acting.
Downside
One biggest disadvantage of the ultrasonic detector is that it sometimes responds to normal environmental vibration that can be caused by a passing car or a plane overhead. Some types of motion detectors use infrared sensors to avoid this problem, but even these detectors the problems cannot be fully eliminated.
Application
Ultrasonic detectors could be used in industry for security purpose.
|
