VORRICHTUNG ZUR ULTRASCHALLUEBERWACHUNG VON RAEUMEN, INSBESONDERE VON KRAFTFAHRZEUG-INNENRAEUMEN

摘要

The surveillance device has an ultrasonic transmitter and an ultrasonic receiver for generating and detecting the sound waves occurring in the surveillance space, said sound waves being detected by an evaluator and, if appropriate, reported in an alarm. In order to obtain a particularly reliable and sensitive device, it is proposed that the transmitter repeatedly radiates a constantly reproducible transmission pulse of defined transmission duration into the surveillance space and the ultrasonic receiver detects the interference field for a measurement time which is exactly matched thereto, said interference field resulting both from the transmission pulses and from the reflection signals in the surveillance space. The time/measured value profile occurring during the measuring time is stored by an evaluator and compared with a profile which has occurred with a preceding transmission pulse. If the detected deviation lies outside a specific tolerance range, the alarm is activated.