Flowmeter with conditioning orifice plate

A method of measuring flow with a differential pressure fluid flow meter for measuring flow of a fluid through a conduit based upon a differential pressure in the fluid generated by the flow of fluid through an orifice plate element disposed between the connecting flanges of conduit sections of a fluid carrying conduit, comprising:

• providing a differential pressure sensor arranged to sense a differential pressure between an upstream tap and a downstream tap in the conduit, wherein the conduit is selected from a plurality of conduits each having a different interior circumference configured to carry the flow of fluid there through;
• providing a flat orifice plate selected from a plurality of flat orifice plates each configured to be positioned between the upstream and the downstream taps in the conduit, where each of the plurality of orifice plates is sized to couple to one of the plurality of conduits having different interior circumferences;
• wherein the plurality of flat orifice plates are configured to be sealed between flanges of the conduit along the interior circumference of the conduit which defines a circular active region of the plurality of flat orifice plates;
• forming four evenly spaced circular orifices in each of the active regions of the plurality of flat orifice plates, the four evenly spaced circular orifices configured to allow the flow of fluid there through and create the differential pressure which is a function of fluid flow rate;
• configuring Xdc which is a distance in a direction perpendicular to an axis of the conduit from the nearest outer circumference of the circular orifices to a projection of a center of the downstream tap on the flat orifice plate;
• configuring Xed which is a distance between outer circumferences of two opposed circular orifices;
• wherein Rb is a ratio of the diameter that locates the centers of the four circular orifices and the interior diameter of the conduit;
• configuring Xdc and Xed such that they are each a function of Rb for each of the plurality of flat orifice plates;
• and
• determining flow rate of the fluid based upon the sensed differential pressure and a discharge coefficient of the flat orifice plate selected from the plurality of flat orifice plates.