Aalborg Instruments Vortex In-Line Flowmeter VXF-07*-6S4*C

Vortices are created when a fluid passes around a bluff
body as shown below. Vortices are alternately shed on each
side of the body, 180 degrees out of phase to each other,
resulting in an oscillating pressure gradient. As flow
increases the frequency of vortices increases in proportion
to the increased flow thereby creating a linear relationship.
Aalborg's unique dual signal processing technology
independently measures each vortex on either side of the
bluff body and filters out non-flow noise. This results in less
noise and higher accuracy throughout the flow range.