(EN) An ultrasonic transducer for a pipe includes an ultrasonic source which produces plane waves. The transducer includes a housing having a face at least a portion of which is curved, through which the plane waves produced from the ultrasonic source disposed in the housing are emitted and directed outward towards the pipe's interior wall so that a full cross-section of the pipe's interior can be measured. A flow meter for detecting fluid flow rates in a pipe. A method for detecting fluid flow rates in a pipe.