Editing Flow measurement (section)

===Orifice plate===
An [[orifice plate]] is a plate with a hole through it, placed perpendicular to the flow; it constricts the flow, and measuring the pressure differential across the constriction gives the flow rate. It is basically a crude form of [[Venturi meter]], but with higher energy losses. There are three type of orifice: concentric, eccentric, and segmental.<ref>Lipták, [https://books.google.com/books?id=ju0U2ItY1QsC&dq=orifice%20plate%20meter%20eccentric%20plate&pg=PA85 ''Flow Measurement''], p. 85</ref><ref>{{cite report|publisher =[[American Gas Association]] |title = Report Number 3: Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids|date = September 2012 |url-access = subscription|url = https://global.ihs.com/doc_detail.cfm?document_name=AGA%20REPORT%20%233%20P1}}</ref>