Sierra INNOVA-FLO 220 - Manual (Page 9)

Series 220/221 Instruction Manual Chapter 1 Introduction
IM-22 1-3
How the Innova-Flo Vortex Flow Meter Operates
Figure 1-1. Series 220 In-Line Vortex Flow Meter
Sierra Series 220 and 221 Innova-Flo ™ Vortex Flow Meters use a unique
velocity sensor head to monitor volumetric flow rate. The built-in flow
computer calculates mass flow rate based on a constant value of fluid
density stored in the instrument’s memory. To measure fluid velocity,
the flow meter incorporates a bluff body (shedder bar) in the flow
stream, and the velocity sensor measures the frequency of vortices cre-
ated by the shedder bar. The velocity sensor head is located downstream
of the shedder bar within the flow body.
Velocity Measurement
The Innova-Flo vortex velocity sensor is a patented mechanical design
that minimizes the effects of pipeline vibration and pump noise, both of
which are common error sources in flow measurement with vortex flow
meters. The velocity measurement is based on the well-known Von Kar-
man vortex shedding phenomenon. Vortices are shed from a shedder bar,
and the vortex velocity sensor located downstream of the shedder bar
senses the passage of these vortices. This method of velocity measurement
has many advantages including inherent linearity, high turndown, reliabil-
ity and simplicity.