This section does not describe a particular type of flowmeter, but rather a design that may be
implemented for several different kinds of flow measurement technologies. When the pipe carrying
process fluid is large in size, it may be impractical or cost-prohibitive to install a full-diameter
flowmeter to measure fluid flow rate. A practical alternative for many applications is the installation
of an insertion flowmeter: a probe that may be inserted into or extracted from a pipe, to measure
fluid velocity in one region of the pipe’s cross-sectional area (usually the center).
A classic example of an insertion flowmeter element is the Annubar, a form of averaging pitot
tube pioneered by the Dieterich Standard corporation. The Annubar flow element is inserted into a
pipe carrying fluid where it generates a differential pressure for a pressure sensor to measure