Abstract: The invention relates to apparatus for ultrasonically measuring physical parameters of flowing media. A measuring path has two ultrasonic converters with transmitting and receiving devices being connected to the converters. The path has at least one component in the direction of flow and over which ultrasonic signals are sent alternately upstream and downstream. A comparator unit connected to the receiving device has an input for a reference signal from the control unit applied thereto at a predetermined time after the time of the transmitter starting signal. The comparator unit generates early or late signals when arrival signals from the receiving device come in earlier or later than the reference signal. A first signal level generator connected to said comparator unit produces a first main signal related to the velocity of sound in said media. A second signal level generator connected to the logic circuit for producing a second auxiliary signal related to the flow velocity of said media.