One of the most common DP Flow Myths is that the rangeability of DP Flow technology is typically 3:1. This misperception is usually promoted by competing technologies that claim “high” rangeability of 20:1 or better. Rangeability is usually defined as the ratio of maximum to minimum flow. There are two definitions of “maximum flow” which are commonly used in specifying the rangeability of a flow meter. It is important to understand the difference between the two methods of defining the maximum flow because it can mean the difference between a flow meter that can measure the flow range of interest and one that can’t. The first way to define “maximum flow” is the maximum flow rate that the flow meter can measure. This is how most flow meters specify rangeability in product literature.
Emerson (2013) Rosemount DP Flowmeter Rangeability