PID Function Block
March 2006
5-81
Figure 5-12. PID Function Block Schematic
B2721 / IL
FF VAL
Alarm
Detection
Operator
Output
PID
Equation
Setpoint
Limiting
Feedforward
Calculation
BKCAL
OUT
OUT
RCAS
OUT
FF
GAIN
FF SCALE
PV
SCALE
PV FILTER
SP HI LIM
SP LO LIM
SP RATE DN
SP RATE UP
Output
Limiting
MODE
BKCAL
IN
TRK
IN D
CAS
IN
IN
TRK
VAL
RCAS
IN
Scaling
and
Filtering
TRK
SCALE
OUT SCALE
Convert
ROUT
OUT
ROUT
IN
OUT
HI LIM
OUT LO LIM
OUT SCALE
HI HI LIM
HI LIM
DV HI LIM
DV LO LIM
LO LIM
LO
LO LIM
Operator
Setpoint
GAIN
RATE
RESET
Service. The BLOCK_ERR [6] parameter shows Out
of service.
You can configure the Man, Auto, Cas, and OOS
modes as permitted modes for operator entry.
Mode Handling
Shed Options—RCAS Mode Only
Shed from or climb to a remote mode is determined by
the parameter SHED_OPT [34]. A block climbs and
sheds through the same path. For example, if
SHED_OPT [34] specifies that a block should shed to
Auto, then, if the block target mode is set to RCas, the
block goes through Auto on the way to RCas. You can
configure the shed option as follows:
Shed With Return Options
Remote cascade or remote output connection failure
shifts actual mode but keeps trying to restore remote
cascade or remote output (in other words, the remote
cascade or remote output target mode stays in effect).
Normal—On failure of a remote connection, the block
attempts to attain the highest permitted non-remote
mode until the remote connection is restored. Cas is
the highest permitted non-remote mode and Auto is is
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