In the U-type mass flowmeter, the shunt pipe at the inlet equally divides the inflow medium into two measuring tubes. Due to the action of driving coils, the two measuring tubes produce relative vibration with the fulcrum as the shaft with a certain natural frequency and a certain amplitude. In the case of no fluid flow, two measuring tubes vibrate in parallel, the signals detected by the inlet and outlet detection coils are the same, and there is no phase difference.
When there is fluid flowing through the measuring tube, due to the opposite vibration direction of the double U-shaped vibrating tube, under the action of Coriolis, the twisting angle is directly proportional to the mass flow of the fluid flowing through the vibrating tube. The twisting angle can be measured by the signal phase difference detected by the inlet and outlet detection coils, that is, mass flow = flowmeter coefficient × phase difference.