Yokogawa EJX930A - Manual (Page 11)

<2. About the EJX Multivariable Transmitter>
2-3
IM 01C25R01-01E
2.3 Flow Calculation (except
Modbus Communication
Type)
There are two flow calculation modes: auto
compensation mode and basic mode.
The FlowNavigator is required to configure auto
compensation mode.
(Please refer to IM 01C25R51-01E for FSA120.)
Sections 2.4 and 2.5 give an overview of the two
calculation functions and explain how to configure
them.
2.4 Auto Compensation
Mode (except Modbus
Communication Type)
Configuration of the fluid physical properties
and the primary device can be performed
from an FlowNavigator dialog window. In auto
compensation mode, all flow factors for flow
calculation are dynamically compensated to an
optimum value with a high level of accuracy. The
flow factors that are automatically compensated are
discharge coefficient, diameter of primary device,
upstream internal pipe diameter, gas expansion
factor, density, and viscosity.
Based Mass Flow Equation
Qm = ε d 2
2∆Pρ
C
(1–β 4 )
4
C, β, ε, d and ρ are dynamically compensated
flow factor.
Qm: Mass Flow
C: Discharge coefficient
β: Diameter ratio
ε: Expansion factor
d: Diameter of primary device
∆P: Differential Pressure
ρ: Density of fluid
Volume Flow Equation
Qv = Qm / ρ
Physical propertyDB
Fluid condition
Flow calculation
standard
Primary element
information
Transmitter
coefficient
Flow
calculation
Transmitter
coefficient
DIPPR* (gas/liquid)
Steam Table
Natural Gas
Diff pressure (DP)
Static pressure (SP)
External Temperature(ET)
FlowNavigator EJX910A/EJX930A
Sensor input (DP, SP, Temp )
Output for
selected PV.
DP, SP, ET
Mass flow
Optimization
F0203.ai
*: AIChE, DIPPR (Design Institute for Physical Properties) is
a registered trademark of American Institute of Chemical
Engineers.
Figure 2.3 Auto Compensation Mode Block Diagram