Abstract: A measurement method for distances between ultrasonic transducers installed on opposite banks of a river or open water channel is provided. Ultrasonic transducer clusters having two transducers spaced by a known distance are used for multichannel ultrasonic flowrate measurement. The distance between ultrasonic transducers installed in the water on both sides of the river is determined by the measurement of the horizontal average flow velocity directly by ultrasonic waves. A calibration and testing method is provided for the distance between two ultrasonic transducers included in the clustered ultrasonic transducer for the calibration and testing method of the flowrate measurement error for a multichannel ultrasonic flowrate measurement system, and for the clustered ultrasonic transducer apparatus.

Abstract: A first measurement unit for untrasonically measuring a flow velocity, a river depth, and an ultrasonic velocity is mounted on floating members. The floating members are connected with a travelling unit for automatically travelling a propeller flowmeter which is used in advance, to thereby measure vertical average flow velocities and river depths at a plurality of positions while moving along a river width. The floating members are provided with ultrasonic vibrators in the center thereof for measuring a river depth and an ultrasonic velocity as well as with ultrasortie vibrator pairs for measuring flow velocities. A second measurement unit for measuring an ultrasonic pulse propagation time period has a unit for calculating an ultrasonic velocity, a river depth, a partial flow quantity and an entire flow quantity, and a unit for controlling movements of the floating members and a distance between the ultrasonic vibrators.