Vortex shedding is a physical phenomenon occurring in nature.  As flow passes a bluff body in the flow stream, vortices are alternately shed on either side of the bluff body.  This effect can be observed in the fluttering of a flag.  The flag pole acts as a bluff body to the wind.  The flag waves in response to the vortices shed as the wind passes the flag pole.  According to well proven physical laws, the frequency at which vortices are alternately shed is directly proportional to the flow velocity.

The vortices create low and high pressure zones behind the bluff body.  The V-Bar uses dual semiconductor strain gauges to detect the pressure exerted by the vortices on the sensing wing.  The strain gauges generate an electric frequency signal, which is proportional to the local velocity at the insertion depth.

The "Smart", microprocessor-based electronics calculates the local velocity, using a linear relationship developed during calibration, between the sensor input frequency and velocity.   The electronics then translates the local velocity into an average flow velocity and then into a flow rate, based on user-selected engineering units.  The 8-character, 2-line, local display alternates between flow rate and totalized flow.  A 4-20 mA current output and a frequency/pulse output are standard.