Abstract: A fluid flow meter comprising a fluid tight housing including an inlet and an outlet; a hollow liner mounted within the housing including at least one slot, the slot for receiving fluid from the inlet and communicating it to the outlet; a magnetic piston slidably positioned within the liner for movement in response to the flow of fluid from the inlet through the slot; and a Hall effect transducer mounted in the housing in substantially side-by-side relation to the piston for producing an electrical signal corresponding to the position of the piston in the cylinder.