An instrument for measuring the volume of flowing gases and liquids. It consists of two parts--the tube through which the fluid flows and a set of indicators which show the Pressures, rate of flow, or quantity discharged. The tube, in the shape of an elongated hourglass, is flanged into a pipeline carrying the fluid. The effect of the tube is to increase the velocity and decrease the pressure at the point where the tube's diameter is reduced. The relationship between the line pressure and the pressure at the narrow "waist" of the tube is used in computing the rate of flow.
