The present invention relates to a magnetic flow controller which transforms a slow reduction in pressure of fluid flow over time to a measurable fluid flow. Once a threshold pressure differential is reached, a flow passage through the flow controller opens rapidly to a relatively large opening, thereby generating a volume of fluid at high flux flowing through the passage, particularly to permit the measurement of the volume of fluid in a conventional flow meter. The device of the present invention integrates this low flux and transforms it to a measurable fluid flux, so that the fluid can be measured by the fluid meter within its optimum error range. This is accomplished while maintaining a pressure drop in the flow meter which is within the permitted standards. Thus, the invention provides relatively sharp shifts between substantially high flux flow and no flow, in a pulse-like manner.