Yokogawa RotaMASS 3-Series - Manual (Page 19)

3. ABOUT FIELdBUS
3-1
IM 01R04B05-00E-E 3rd edition July 30, 2010-00 all Rights Reserved. Copyright © 2005, Rota Yokogawa
3. ABOUT FOUNdATION FIELdBUS
3.1 Outline
Fieldbus is a bi-directional digital communica-
tion protocol for field devices, which offers an
advancement in implementation technologies for
process control systems and is widely employed
by numerous field devices.
the FounDatIon Fieldbus communication
type of the Rotamass employs the specification
standardized by the FounDatIon Fieldbus,
and provides interoperability between Yokogawa
devices and those produced by other manufactur-
ers. Featuring 6 aI and two It function blocks in
each, the Fieldbus communication type’s software
enables a flexible instrumentation system to be
implemented.
For information on other features, engineering, de-
sign, construction work, startup and maintenance
of Fieldbus, refer to “Fieldbus technical Informa-
tion” (tI 38K3a01-01E).
3.2 Internal Structure of
rOTAMASS
Each Rotamass contains two Virtual Field Devices
(VFDs) that share the following functions.
3.2.1 System/Network Management VFd
• Sets node addresses and Physical Device tags
(PD tag) necessary for communication.
• Controls the execution of function blocks.
• Manages operation parameters and com-
munication resources (Virtual Communication
Relationship: VCR).
3.2.2 Function Block VFd
(1) resource (rS) block
• Manages the status of Rotamass hardware.
• automatically informs the host of any detected
faults or other problems.
(2) Transducer (TB) block
• Converts the flow sensor output to the mass
flow rate signal and transfers to an aI function
block (aI1).
- Converts the flow sensor output to the
process fluid density and transfers to an aI
function block (aI3).
- Converts temperature sensor output to the
process fluid temperature and transfers to
an aI function block (aI4).
- Calculates the volumetric flow rate from
the fluid density and the mass flow rate
and transfers to an aI function block (aI2).
(3) AI function blocks (six)
• the aI blocks condition raw data from the
transducer block, including scaling and damp-
ing (with a first-order lag), and allow input
simulation.
• aI1 outputs mass flow rate signals, and aI2
outputs volumetric flow rate signals.
• aI3 outputs density signals, and aI4 outputs
temperature signals.
• aI5 outputs concentration measurement
signals (option), and aI6 outputs net flow rate
signals (option).
(4) IT Integrator blocks (two)
• It1 totalizes mass-, volume or net flow rate.
• It2 totalizes mass-, volume or net flow rate.
(5) PId function block (optional)
• Performs the PID computation based on the
deviation of the measured value from the set-
point.