Variable orifice gas flow sensing head

摘要

A gas flow meter employing means for obtaining a differential pressure across a resistance orifice in a line of gas flow. Although flow through the orifice may be turbulent thus making the differential pressure non linear with respect to the amount of flow, the effect of that turbulence is offset by the provision of a hinged flap within the orifice which opens upon increase in gas flow thereby lowering the orifice's resistance to that flow. Because of the variable resistance orifice the resultant pressure differential is linear with respect to the amount of flow. The differential pressure is sensed by pressure tubes disposed on opposite sides of the orifice and the hinged flap is arranged to flex over the downstream pressure tube so as to protect it from eddy currents. Moreover, the flap is hinged at the top and opens from the bottom whereby free liquid may pass through the orifice without any significant change in calibration.