This document specifies general requirements, minimum performance requirements and test procedures for open channel instrumentation used to determine either volumetric flow-rate and/or total volume passed of waters in artificial open channels. It covers the following technology categories: Level sensors with associated electronics designed to be used with a conventional gauging structure. (The requirements and test procedures for gauging structures, such as weirs and flumes, are excluded. The stage discharge characteristics for many of these structures are established and published in national and international standards). Fluid velocity sensors. Integrated velocity area devices comprising level and velocity sensors that may be separate or combined in a single assembly. Velocity sensors that determine the mean water velocity through a channel. It is recognized that for some OCIs, certain tests cannot be carried out.