For example, if the flow in the meter tube is moving upwardly during the first half of the process, the fluid being forced into the meter resists the upward force and pushes the tube downward. Conversely, the liquid that is flowing out of the meter resists the decrease in vertical movement and pushes up on the tube, causing the flow meter tubes to twist. During the second half, the flow will move downwardly and cause the tube to twist in the opposite direction. This creates a phase difference, or time lag, between the inlet sides and outlet sides. The phase difference is affected directly by the mass that is passing through the tubes.