Abstract: The invention relates to an ultrasonic tomograph for spatial and temporal characterisation of fluids in motion such as air and water. This tomograph comprises a plurality of pairs of emitting-receiving ultrasonic probes, whereas each pair may be inscribed, diametrally opposite, on a circle centred round a flow axis of the fluid. The probes are therefore laid out on either side of the flow and will neither modify nor disturb the flow. Each probe may be displaced in a plane perpendicular to the flow axis. Indeed each probe is allocated a stepping motor. Each probe is a piezoelectric ceramic transducer which does not drift with time and which does not require any re-calibration, which provides the tomograph according to the invention stability over time. Moreover this tomograph is robust since these ultrasonic probes may be used under extreme conditions. The frequency of ultrasounds ranges between 30 kHz and 300 kHz.