Abstract: A flowmeter device for measuring a flow rate of a fluid includes a conduit for the fluid flow. The conduit is characterized by a cross-sectional area and includes at least one section within which the cross-sectional area is different from the cross-sectional area of at least one other section of the conduit. The device also includes a reference tube separated from the conduit by a wall and at least one opening in the wall between the section and the reference tube. The device includes a flexible diaphragm forming a space between the diaphragm and a region of the wall at the section of the conduit, and which includes the opening, to inhibit flow of the fluid between the conduit and the reference tube.