Patent ID: 6263731
Filing Date: 2001-07-24
Classification: G01F,G01N,Y10S

Abstract:
A method for monitoring a predetermined level of a material in a container with the aid of two ultrasonic transducers mounted in line with the level to be monitored on the container such that an interspace exists between the ultrasonic transducers into which the material enters on attaining the level to be monitored, whereby the one ultrasonic transducer is an emitter transducer energized at predetermined points in time to emit ultrasonic pulses into the interspace whilst the other ultrasonic transducer is a detector transducer which detects the ultrasonic pulses during a first time window corresponding to the transit time of said ultrasonic pulses from said emitter transducer to said detector transducer in air and converts the detected ultrasonic pulses into electrical detection signals, the analysis of which indicates whether material is in the interspace between the ultrasonic transducers wherein said emitter transducer emitting said ultrasonic pulses is energized at a frequency which is so low that said ultrasonic pulses are transmitted through said interspace to said detector transducer even when said interspace is filled with air and it is determined whether said detector transducer outputs a detection signal during the first time window.