Coriolis meters artificially introduce positive and negative Coriolis acceleration into the metering process. As illustrated in the diagram above, the fluid media is split and redirected through two curved tubes. An oscillating excitation force is applied to the tubes via miniature velocity transducers or electric coils, causing vibration that is measured by magnetic sensors. Coriolis flow meters vibrate at a very small amplitude, usually less than 0.1” (2.5 mm). This frequency is near the natural frequency of the device, which is usually roughly 80 Hz.
When no flow is present, the tubes vibrate and the sine wave outputs of each hall-effect transducer are in phase. When flow is initiated, the fluid flowing through the tubes induces a rotation or twist to the tube due to acceleration of the Coriolis Effect, which operates in opposite directions on either side of the applied force.
For example, when the flow meter tube is moving upward during the first half of a cycle, the fluid flowing into the meter resists being forced up and pushes down on the tube. Conversely, liquid flowing out of the meter resists having its vertical motion decreased by pushing up on the tube.
This action causes the flow meter tube to twist. When moving downward during the second half of the vibration cycle, the tube twists in the opposite direction. This twist results in a phase difference (time lag) between the inlet and outlet sides, and this phase difference is directly affected by the mass passing through the tube.