Abstract: A flow meter comprises a conduit adapted to conduct a flow of a fluid, a stop in the conduit, and a body that is movably received in the conduit, is normally kept in engagement with the stop by the fluid flow, and has at least a portion of a magnetically responsive material. An electromagnet is located outside the conduit in a position upstream from the stop, relative to the direction of the fluid flow, and has its poles located such as to impose a magnetic force on the magnetically responsive material of the body when it is energized. A ramp current generator energizes the electromagnet so as to progressively increase the magnetic force that it produces until the magnetic force is sufficient to move the body against the fluid flow and attract the body to a position between the poles.