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SC100/200 Series Function Block Application Manual EM-6460-C
4.3.4 OVERRIDE CONTROL
Override control is used to take control of an output from one loop to allow a more important loop to manipulate the output,
thus the output from two or more controllers are combined to manipulate a final control element. It is a typical application of
external feedback (output tracking) function.
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LOOP CONFIGURATION EXAMPLE
• Temperature control of a tank is the main purpose of the system.
• The FIC is used to maintain steam flow within a preset limit.
• The TIC output is repeated at the FIC output when the TIC takes control.
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BLOCK DIAGRAM
steam
flow
temp
PV
FIC
SEC
TIC
PRI
MV
PV
MV
flow
temp
PV
external feedback
Deviation
Alarm
Absolute
Value
Absolute
Value
external feedback
FIC
G03
TIC
G02
MV
A/M
X2
dev
X1
dev
MV
MV
PV
ABS
G32
DVA
G30
ABS
G31
SEQ
G81
positive deviation
output
Sequence