Abstract: A single straight tube flowmeter has a body; a tube through which a flow of fluid passes; two systems of excitation of oscillations in two planes which are perpendicular to one another and including adaptor units; a block of processing of information data including a phase shift of the adaptors located in one plane, frequency of oscillations of the tube, and temperatures of the tube and the body and outputting results of measurement of a mass flow rate and density of the fluid; and components for imparting to the tube a rotary motion relative to its neutral immovable position to increase accuracy of measurements by suppressing vibration disturbances.