Abstract: A restriction flowmeter including a cylinder through whose interior a fluid to be measured flows and a pipe for forming a restriction structure penetrating the cylinder in a direction perpendicular to the central axis of the cylinder, the pipe having a diameter smaller than the inner diameter of the cylinder, characterized in that a first pressure measuring hole is formed on the most restricted cross section perpendicular to the flow direction and a second pressure measuring hole is formed on a wall of the cylinder located upstream which is away from the most restricted cross section by ½ or more of the inner diameter of the cylinder.

Abstract: An air flow rate measuring apparatus includes a casing having opposite open ends, a flow rectifier mounted within the casing at an upstream-side portion thereof with respect to a direction of flow of fluid to be measured, and at least one fluid pressure detector which is mounted within the casing, and is disposed downstream of the flow rectifier, the fluid pressure detector including at least one differential pressure detector member. The differential pressure detector member includes a pair of tubular members of an identical configuration, and each of the tubular members has a flattened shape having opposed narrow side walls and opposed wide side walls, and at least one pressure-measuring port is formed through one of the opposed narrow side walls. The differential pressure detector member further includes a pair of plug members mounted on and closing opposite open ends of each of the tubular members, respectively, one of the pair of plug members having a pressure outlet port.