The double annular measuring tube Coriolis Mass Flowmeter consists of a pair of parallel helical tubes with a short straight tube. In the middle position D of the pipe is equipped with a driver. The two measuring tubes are subjected to periodic opposite vibrations. Two sensors are arranged at the two ends of the elliptical spiral tube, equidistant from the middle point D. Measure the relative velocity of motion between the pipes at these two points. The phase difference between these two relative speeds is proportional to the mass flow rate of the fluid flowing through the measuring tube. When the fluid in the measuring tube does not flow, the deformation of the tube caused by the vibration force is the same on both sides of the middle point. At the two measuring points at the sensor, the phase difference of the measured vibration displacement is zero. When the fluid flows in the measuring tube, before the point of maximum amplitude, the fluid particle produces an effect opposite to the vibration direction due to the Coriolis force. force. After this point, however, a force acting in the same direction as the vibration is produced. Since the force on the two measuring tubes at the same moment is equal in size and opposite in direction, it is reflected that the moving speed of the tubes at the measuring points at the two sensors is increased or decreased, and the phase difference between these two points can be measured to obtain a pass Measure the mass flow rate of the tube fluid.