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Instruction Manual
IM-106-880C, OI
September 2009
7-49
Hazardous Area OCX 8800
If the instrument connected to the AI block fails, you can place the AI block in
Manual mode and set the output to some nominal value for use in the
Integrator function block. In this case, IN at the slave PID block is constant
and prevents the integral term from increasing or decreasing.
Figure 7-21. Function Block Diagram for Cascade Control with Override
38740101
PID
Function
Block
AO
Function
Block
PID
Function
Block
Control
Selector
Function
Block
PID
Function
Block
PID
Function
Block
AI
Function
Block
Configured for High Selection
Master Controller
Slave Controller
Master Controller
OUT
OUT
OUT
OUT
OUT
IN_1
CAS_IN
CAS_IN
IN
SEL_1
SEL_2
BKCAL_SEL_2
BKCAL_SEL_1
BKCAL_OUT
BKCAL_IN