Image Number 2 for United States Patent #4297899.
A compact fluid flow sensor of the variable area type is disclosed which can accurately measure a broad range of flow rates and can be installed in any position relative to the horizontal plane and which is therefore particularly adaptable for use with vehicular fuel systems. The sensor comprises connected input and output housing members that retain between them a flexible diaphragm having an annular central orifice member. An adjustable needle valve is positioned within the orifice member to form a small, variable opening for fluid. The orifice member is connected to a core member of a differential transformer whose windings are connected to a circuit producing output signal responsive to the linear position of the core member. The varying pressure differential due to fluid flow rate created on opposite sides of the diaphragm causes the orifice member, and its attached core member, to move relative to the windings and produce an output from the differential transformer proportional to the fluid flow rate.