Abstract: The present invention is related to a device and a method using said device for the measurement and classification of bubble sizes in a liquid medium. This invention comprises two electric emitter and receiver transducers located at an angle lower than 180 degrees one with respect to the other, and ultrasonic signal emitter and receiver circuits operatively connected to the electric emitter and receiver transducer respectively. The classification of the bubble sizes is based on two-dimensional time domain patterns that represent the trace of the bubbles when they cross a generated ultrasonic field. This invention is of great utility to track processes involving the generation of bubbles in liquid media such as the froth flotation in mining.