Abstract: The invention relates to ultrasonic apparatus for measuring flow quantities and related parameters of a liquid flowing with a free surface in a channel. Two transducers are provided with one being mounted in the channel below the level of the flowing liquid. The other transducer is mounted on a float member which is floatable on the surface of the liquid. The transducers are effectively positioned from each other and a measuring path is formed therebetween which has components in the vertical direction and in the direction of flow. There is a measuring circuit for determining the transit times of the ultrasonic waves in both directions and an evaluating circuit for determining the desired quantities with regard to the transit times.

Abstract: The invention relates to ultrasonic apparatus for measuring flow quantities and related parameters of a liquid flowing with a free surface in a channel. Two transducers are mounted in longitudinally spaced relation to each other in the channel and below the level of the flowing liquid. The transducers are positioned and directed so that the effective measuring path therebetween is reflected from the underside of the liquid surface level and has components in the vertical direction and in the direction of flow. There is a measuring circuit for determining the transit times of the ultrasonic waves in both directions and an evaluating circuit for determining the desired quantities with regard to the transit times.