Measuring fluid flow is one of the most important aspects of process control. In fact, it may well be the most frequently measured process variable. This bulletin describes the nature of flow and factors affecting it. Devices commonly used to measure flow are presented, as is a discussion on accuracy and how it is typically specified. For quick reference, a table listing the primary characteristics of flow metering devices is included along with a conversion chart for the various measurement units encountered in dealing with flow.
EMERSON (2001) Fundamentals of Flow Metering