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A process flow device that includes a self-averaging orifice plate type of primary flow element for measuring, by a differential pressure process, the volumetric rate of fluid flow at a point in a fluid carrying conduit where the velocity profile of the fluid is asymmetric with respect to the longit

A process flow device that includes a self-averaging orifice plate type of primary flow element for measuring, by a differential pressure process, the volumetric rate of fluid flow at a point in a fluid carrying conduit where the velocity profile of the fluid is asymmetric with respect to the longitudinal axis of the conduit. The improved flow element comprises a planar flow-impeding plate disposed transversely across the interior of the conduit and perpendicular to the longitudinal axis thereof. The plate includes at least three circular apertures eccentrically disposed with respect to the longitudinal axis of the conduit to create static pressure averaging on the downstream side of the plate. Upstream and downstream static pressure sensing ports are respectively provided on opposite sides of the flow impeding plate.

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What is claimed is: 1. An averaging orifice plate fluid flow meter for measuring the volumetric rate of fluid in a conduit, comprising: a constant diameter conduit for carrying fluid from an upstream to a downstream location; a planar flow impedance plate disposed transversely across the interior o

What is claimed is: 1. An averaging orifice plate fluid flow meter for measuring the volumetric rate of fluid in a conduit, comprising: a constant diameter conduit for carrying fluid from an upstream to a downstream location; a planar flow impedance plate disposed transversely across the interior of the conduit; a set of at least three circular apertures in the planar flow impedance plate eccentrically disposed with respect to the longitudinal axis of the conduit, wherein the set of at least three circular apertures defines all of the circular apertures disposed through the planar flow impedance plate that are eccentrically disposed with respect to a center point of the planar flow impedance plate, wherein each of the set of at least three circular apertures has a center point that is disposed on a single circle having a center point coincident with the center point of the planar flow impedance plate so that the set of at least three circular apertures are disposed symmetrically around the center point of the planar flow impedance plate; a first static pressure sensing element disposed within the conduit upstream of the planar flow impedance plate and proximate thereto; a second static pressure sensing element disposed within the conduit downstream of the planar flow impedance plate and proximate thereto; and a transmitter coupled to the first and second static pressure sensing elements to determine the volumetric rate of fluid in the conduit. 2. The averaging orifice plate fluid flow meter for measuring the volumetric rate of fluid in a conduit of claim 1, wherein each of the first and second pressure sensing elements comprises a bore disposed through the constant diameter conduit. 3. The averaging orifice plate fluid flow meter for measuring the volumetric rate of fluid in a conduit of claim 1, wherein constant diameter conduit includes first and second sections separated by the planar flow impedance plate. 4. The averaging orifice plate fluid flow meter for measuring the volumetric rate of fluid in a conduit of claim 3, wherein each of the first and second sections includes a mounting flange disposed thereon. 5. An averaging differential pressure primary flow measuring element for insertion between sections of a fluid carrying conduit, comprising: first and second annular flanges having interior openings having a circular cross section of the same diameter and that correspond in shape and size to the inside cross section of the conduit; a flow impedance plate having a center point, the flow impedance plate being disposed between the first and second annular flanges transverse to a longitudinal axis of the interior openings of the annular flanges so that the center point of the flow impedance plate is coaxial with the longitudinal axis of the interior openings of the annular flanges; and a set of circular holes disposed through the flow impedance plate, the set of circular holes defining a plurality of circular holes and defining all of the circular holes disposed through the flow impedance plate that are eccentrically disposed with respect to the center point of the flow impedance plate, wherein each of the set of circular holes has a center point that is disposed on a single circle having a center point coincident with the center point of the flow impedance plate so that the plurality of circular holes within the set of circular holes are disposed symmetrically around the center point of the flow impedance plate. 6. The averaging differential pressure primary flow measuring element of claim 5, wherein each of the plurality of circular holes within the set of circular holes has the same diameter. 7. The averaging differential pressure primary flow measuring element of claim 6, wherein each of the plurality of circular holes within the set of circular holes includes a first edge point disposed proximate to a point at which a wall defining the interior opening of one of the annular flanges meets the flow impedance plate. 8. The averaging differential pressure primary flow measuring element of claim 7, wherein each of the plurality of circular holes within the set of circular holes includes a second edge point disposed proximate to a second edge point of another one of the plurality of circular holes within the set of circular holes. 9. The averaging differential pressure primary flow measuring element of claim 8, wherein the distance between the first edge point and the point at which the wall defining the interior opening of one of the annular flanges meets the flow impedance plate is approximately the same as the distance between the second edge points of adjacent ones of the plurality of circular holes within the set of circular holes. 10. The averaging differential pressure primary flow measuring element of claim 5, wherein each of the plurality of circular holes within the set of circular holes includes an edge point disposed proximate to an edge point of another one of the plurality of circular holes within the set of circular holes. 11. The averaging differential pressure primary flow measuring element of claim 5, wherein the area defined by the plurality of circular holes within the set of circular holes is less than the area defined by the flow impedance plate bounded by the interior openings of the annular flanges and not defined by any of the plurality of circular holes within the set of circular holes. 12. The averaging differential pressure primary flow measuring element of claim 5, wherein the center point of each of the plurality of circular holes within the set of circular holes is disposed closer to an interface at which a wall defining the interior opening of one of the annular flanges meets the flow impedance plate than to the center point of the flow impedance plate. 13. The averaging differential pressure primary flow measuring element of claim 5, wherein the plurality of circular holes includes three circular holes. 14. The averaging differential pressure primary flow measuring element of claim 13, wherein the three circular holes are disposed on the circle so that a set of lines connecting the center points of adjacent ones of the three circular holes forms an equal-sided triangle around the center point of the flow impedance plate. 15. The averaging differential pressure primary flow measuring element of claim 5, wherein the plurality of circular holes includes four circular holes. 16. The averaging differential pressure primary flow measuring element of claim 15, wherein the four circular holes are disposed on the circle so that a set of lines connecting the center points of adjacent ones of the four circular holes forms a square around the center point of the flow impedance plate. 17. The averaging differential pressure primary flow measuring element of claim 5, wherein the plurality of circular holes includes five circular holes. 18. The averaging differential pressure primary flow measuring element of claim 17, wherein the five circular holes are disposed on the circle so that a set of lines connecting the center points of adjacent ones of the five circular holes forms a pentagon around the center point of the flow impedance plate. 19. The averaging differential pressure primary flow measuring element of claim 5, wherein the plurality of circular holes includes six circular holes. 20. The averaging differential pressure primary flow measuring element of claim 19, wherein the six circular holes are disposed on the circle so that a set of lines connecting the center points of adjacent ones of the six circular holes forms a hexagon around the center point of the flow impedance plate. 21. The averaging differential pressure primary flow measuring element of claim 5, wherein the first and second annular flanges are mounting flanges. 22. The averaging differential pressure primary flow measuring element of claim 5, wherein the first and second annular flanges are mounting flanges and further including first and second pressure conducting bores radially disposed in the first and second annular mounting flanges for establishing fluid communication between the respective interior openings in the first and second annular mounting flanges and circumferential outside surfaces of the first and second annular mounting flanges. 23. The averaging differential pressure primary flow measuring element of claim 5, wherein each of the circular holes within the plurality of circular holes has opposite circumferential edges, and wherein one of the circumferential edges of each of the circular holes within the plurality of circular holes is beveled. 24. The averaging differential pressure primary flow measuring element of claim 5, wherein the set of circular holes defines all of the circular holes disposed through the flow impedance plate. 25. An averaging differential pressure primary flow measuring element for insertion between sections of a fluid carrying conduit, comprising: an integrally formed annular ring having flat parallel sides with an interior opening having a circular cross section of the same diameter as and that corresponds in shape and size to the inside cross section of the conduit; a flow impedance plate disposed transversely across the interior opening in the annular ring and parallel to the sides of the annular ring, the flow impedance plate having a center point that is coaxial with a longitudinal axis of the interior opening of the annular ring; and a set of circular holes disposed through the flow impedance plate, the set of circular holes defining a plurality of circular holes and defining all of the circular holes disposed through the flow impedance plate that are eccentrically disposed with respect to the center point of the flow impedance plate, wherein each of the set of circular holes has a center point that is disposed on a single circle having a center point coincident with the center point of the flow impedance plate so that the plurality of circular holes within the set of circular holes are disposed symmetrically around the center point of the flow impedance plate. 26. The averaging differential pressure primary flow measuring element of claim 25, further including first and second pressure conducting bores radially disposed in the annular ring on opposite sides of the flow impedance plate. 27. The averaging differential pressure primary flow measuring element of claim 26, further including an elongated mounting stem radially extending from a circumferential outside surface of the annular ring and having first and second conduits disposed longitudinally therethrough that communicate with the respective first and second pressure conducting bores. 28. An averaging differential pressure flow element for determining the volumetric rate of fluid flow in a circular conduit of constant diameter on either side of the flow element, comprising: a fluid flow section with a circular central opening that corresponds in shape and size to the inside cross section of the circular conduit; a flat disk, congruent with the circular central opening, and having a center point, said flat disk being disposed within the circular central opening within a plane that is perpendicular to the longitudinal axis of the circular central opening; and a set of circular holes disposed through the flat disk, the set of circular holes defining a plurality of circular holes and defining all of the circular holes disposed through the flat disk that are eccentrically disposed with respect to the center point of the flat disk, wherein each of the set of circular holes has a center point that is disposed on a single circle having a center point coincident with the center point of the flat disk so that the plurality of circular holes within the set of circular holes are disposed symmetrically around the center point of the flat disk. 29. The averaging differential pressure flow element of claim 28, further including a differential pressure sensor fluidly coupled to either side of the flat disk and a transmitter coupled to the differential pressure sensor. 30. The averaging differential pressure flow element of claim 28, further including, a supporting arm extending radially from the fluid flow section, said arm including first and second interiorly disposed fluid transportation conduits that extend into the fluid flow section, and first and second pressure sensing ports communicating with the interior opening of the fluid flow section on respective opposite sides of the flat disk. 31. The averaging differential pressure flow element of claim 28, wherein each of the plurality of circular holes within the set of circular holes includes a first edge point disposed proximate to a point at which a wall defining the circular central opening of the fluid flow section meets the flat disk. 32. The averaging differential pressure flow element of claim 31, wherein each of the plurality of circular holes within the set of circular holes includes a second edge point disposed proximate to a second edge point of another one of the plurality of circular holes within the set of circular holes. 33. The averaging differential pressure flow element of claim 32, wherein the distance between the first edge point and the point at which the wall defining the circular central opening of the fluid flow section meets the fiat disk is approximately the same as the distance between the second edge points of adjacent ones of the plurality of circular holes within the set of circular holes. 34. The averaging differential pressure flow element of claim 28, wherein each of the plurality of circular holes within the set of circular holes includes an edge point disposed proximate to an edge point of another one of the plurality of circular holes within the set of circular holes. 35. The averaging differential pressure flow element of claim 28, wherein the area defined by the plurality of circular holes within the set of circular holes is less than the area defined by the flat disk bounded by the circular central opening of the fluid flow section and not defined by any of the plurality of circular holes within the set of circular holes. 36. The averaging differential pressure flow element of claim 28, wherein the center point of each of the plurality of circular holes within the set of circular holes is disposed closer to an interface at which a wall defining the central circular opening of the fluid flow section meets the flat disk than to the center point of the flat disk. 37. The averaging differential pressure flow element of claim 28, wherein the plurality of circular holes includes three circular holes. 38. The averaging differential pressure flow meter of claim 37, wherein the three circular holes are disposed on the circle so that a set of lines connecting the center points of adjacent ones of the three circular holes forms an equal-sided triangle around the center point of the flat disk. 39. The averaging differential pressure flow element of claim 28, wherein the plurality of circular holes includes four circular holes. 40. The averaging differential pressure flow element of claim 39, wherein the four circular holes are disposed on the circle so that a set of lines connecting the center points of adjacent ones of the four circular holes forms a square around the center point of the flat disk. 41. The averaging differential pressure flow element of claim 28, wherein the plurality of circular holes includes five circular holes. 42. The averaging differential pressure flow element of claim 41, wherein the five circular holes are disposed on the circle so that a set of lines connecting the center points of adjacent ones of the five circular holes forms a pentagon around the center point of the flat disk. 43. The averaging differential pressure flow element of claim 28, wherein the plurality of circular holes includes six circular holes. 44. The averaging differential pressure flow element of claim 43, wherein the six circular holes are disposed on the circle so that a set of lines connecting the center points of adjacent ones of the six circular holes forms a hexagon around the center point of the flat disk. 45. The averaging differential pressure flow element of claim 28, further including first and second pressure conducting bores radially disposed in the fluid flow section on opposite sides of the flat disk. 46. The averaging differential pressure flow element of claim 45, further including an elongated mounting stem radially extending from a circumferential outside surface of the fluid flow section and having first and second conduits disposed longitudinally therethrough that communicate with the respective first and second pressure conducting bores. 47. The averaging differential pressure flow element of claim 28, wherein each of the circular holes within the plurality of circular holes has opposite circumferential edges, and wherein one of the circumferential edges of each of the circular holes within the plurality of circular holes is beveled. 48. The averaging differential pressure flow element of claim 28, wherein the set of circular holes defines all of the circular holes disposed through the flat disk. 49. The averaging differential pressure flow element of claim 28, wherein the fluid flow section includes an annulus defining the circular central opening. 50. The averaging differential pressure flow element of claim 28, wherein the fluid flow section includes first and second flanges on either side of the circular central opening.