Method and device for monitoring a predetermined filling level in a container

摘要

The method involves using two ultrasound transducers, which are assembled at the height of the fill level, such that a gap (20) is formed between them, through which the content of the container enters if it reaches the fill level to be supervised. One ultrasound transducer is a transmitter (24), which is triggered at predetermined broadcasting intervals to emit ultrasound pulses. The other ultrasound transducer is a detector (28), which transforms received ultrasound pulses into electric signals. An evaluation of the electric signals determines whether the content is in the interval between the ultrasound transducers. The transmission of ultrasound pulses is triggered with a frequency which is so low, that the ultrasound pulses are also transferred through the interval to the detector if the interval is filled with air. After each broadcasting interval, it is determined whether the detector produces a reception signal in a time interval, which corresponds to the duration of the ultrasound pulses from the transmitter the detector in air.