Apparatus for measuring the flow quantity or associated parameters of a liquid with two ultrasonic transducers

Claim 1

Apparatus for measuring the flow quantity or associated parameters such as depth of liquid and mean flow speed of a liquid flowing with a free surface in a channel, comprising, a channel through which a liquid is flowable, two ultrasonic transducers operating alternately with respect to each other as transmitter and receiver, one of said transducers being mounted in the defining wall of said channel below the intended surface level of said liquid, a float member floatable on the surface of said liquid, said other transducer being mounted on said float member, said float member being positioned so that said transducers are spaced from each other and form between each other a measuring path with a component in the direction of flow, a measuring circuit for determining the transit times of the ultrasonic waves in both directions, an evaluating circuit for determining the desired quantities with regard to said transit times, and each said transducer emitting a sound cone with a sufficient aperture angle so that within the range of expected liquid level fluctuations the receiving transducer is still within the reflection space of the emitting sound cone.