Emerson Fisher Fieldvue DVC6030f - Setting the Output

DVC6000f Series
March 2006
5-68
Figure 5-9. Analog Output Function Block Schematic
B2717 / IL
CAS IN
Position
Feedback
Analog
Output
Access
Analog
Output
Access
Analog
Input
Shed
Mode
SP
HI/LO
Limit
SP
Rate
Limit
Convert
and Status
Calculation
BKCAL
OUT
OUT
RCAS
OUT
RCAS
IN
SP
RATE DN
SP RATE UP
SP
WRK
PV
SCALE
IO
OPTS
Operator
Setpoint
READ
BACK
PV
SP
LOW LIM
SP HI LIM
CHANNEL
MODE
limited SP [8] condition is reflected in the
BKCAL_OUT [25] status. When simulation is enabled
through the SIMULATE [10] attribute, you can set the
value and status for PV [7] and READBACK [16].
When the block is in Cas mode and the CAS_IN [17]
input goes bad, the block sheds mode to the next
permitted mode.
Setting the Output
To set the output for the AO block, you must first set
the mode to define the manner in which the block
determines its setpoint. In Manual mode the value of
the output attribute (OUT [9]) must be set manually by
the user, and is independent of the setpoint. In
Automatic mode, OUT [9] is set automatically based
on the value specified by the set point (SP [8]) in
engineering units and the I/O Options attribute. In
addition, you can limit the SP [8] value and the rate at
which a change in the SP [8] is passed to OUT [9].
In Cascade mode, the cascade input connection
(CAS_IN [17]) is used to update the SP [8]. The back
calculation output (BKCAL_OUT [25]) is wired to the
back calculation input (BKCAL_IN [27]) of the
upstream block that provides CAS_IN [17]. This
provides bumpless transfer on mode changes and
windup protection in the upstream block.
Note
You must wire BKCAL_OUT [25] to
BKCAL_IN [27] of the upstream block
that provides CAS_IN [17]. Otherwise,
the AO the upstream block will not
initialize properly, and the setpoint at
CAS_IN [17] will not be passed to OUT
[9].
The OUT [9] attribute or an analog readback value,
such as valve position, is shown by the process value
(PV [7]) attribute in engineering units.
To support testing, you can enable simulation, which
allows you to manually set the channel feedback.
There is no alarm detection in the AO function block.
To select the manner of processing the SP and the
channel output value configure the setpoint limiting
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