About Fieldbus; Outline; Internal Structure Of Digitalyewflo; System/Network Management Vfd - YOKOGAWA digitalYEWFLO Series User Manual

3.

ABOUT FIELDBUS

3.1

Outline

Fieldbus is a bi-directional digital communication
protocol for field devices, which offers an
advancement in implementation technologies for
process control systems and is widely employed by
numerous field devices.
The Fieldbus communication type of the
digitalYEWFLO employs the specification
standardized by the Fieldbus F
provides interoperability between Yokogawa
devices and those produced by other
manufacturers. Featuring two AI and two DI function
blocks in each, the Fieldbus communication type's
software enables a flexible instrumentation system
to be implemented.
For information on other features, engineering,
design, construction work, startup and maintenance
of Fieldbus, read "Fieldbus Technical Information"
(TI 38K03A01-01E).
3.2 Internal Structure of
digitalYEWFLO
Each digitalYEWFLO 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
communication resources (Virtual
Communication Relationship: VCR).
, and
OUNDATION
<3. ABOUT FIELDBUS>

3.2.2 Function Block VFD

(1) Resource (RS) block
• Manages the status of digitalYEWFLO
hardware.
• Automatically informs the host of any detected
faults or other problems.
(2) Transducer (TR) block
• Converts the flow sensor output to the
volumetric flow rate signal and transfers to an AI
function block (AI1).
• With the option /MV
- Converts temperature sensor output to the
process fluid temperature and calculates the
fluid density.
- Calculates the mass flow rate from the fluid
density thus obtained and the volumetric flow
rate obtained with the flow sensor.
- Transfers these calculation results to AI
function blocks.
• Transfers limit switch signals to DI function
blocks.
(3) AI function blocks (three)
• Output flowrate and temperature.
• Condition raw data from the TR block.
• Carry out scaling and damping (with a first-
order lag), and allow input simulation.
(4) DI function blocks (two)
• Limit switches for the flow rate and temperature
(option /MV).
(5) IT function block (one)
• Accumulate given values.
(6) AR function block (one)
• Calculate input values.
(7) PID function block (option /LC1)
• Performs the PID computation based on the
deviation of the measured value from the
setpoint.
3-1
IM 01F06F00-01EN