Sierra INNOVA-MASS 241-VTP - Manual (Page 9)

Series 24-HP Instruction Manual Chapter 1 Introduction
IM-24-HP 1-3
How the Innova-Mass Vortex Mass Flow Meter Operates
Figure 1-1. In-Line Vortex Multi-Parameter Mass Flow Meter
Sierra Series 240 and 241 Innova-Mass™ Multi-Parameter Vortex Mass
Flow Meters use a unique sensor head to monitor mass flow rate by di-
rectly measuring three variables–fluid velocity, temperature and pressure.
The built-in flow computer calculates the mass flow rate and volumetric
flow rate based on these three direct measurements. The velocity, tem-
perature and pressure sensing head is built into the vortex meter’s flow
body. To measure fluid velocity, the flow meter incorporates a bluff
body (shedder bar) in the flow stream and measures the frequency of vor-
tices created by the shedder bar. Temperature is measured using a plati-
num resistance temperature detector (PRTD). Pressure measurement is
achieved using a solid-state pressure transducer. All three elements are
combined into an integrated sensor head assembly located downstream of
the shedder bar within the flow body.
Velocity Measurement
The Innova-Mass 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.