Abstract: Device for measuring the volumetric flow rate of a fluid flowing through a generally tubular body, wherein a swirling motion is imparted to the fluid by a precessing means, comprising a device producing a variable frequency signal depending on the precession motion of the fluid, associated with a logical means arranged for correcting said frequency, characterized in that the precessing means comprises in succession, in the flowing direction of the fluid, a first cylindrical duct communicating with a converging cylindrical-conical axial chamber through a second duct the axis of which is displaced and inclined in relation to the axis of said chamber, the latter communicating co-axially with a cylindrical terminal duct through a third cylindrical duct of restricted diameter connected to said terminal duct by a diverging conical enlargement.