Fisher FIELDVUEDVC6200f Instruction Manual page 247

Instruction Manual
D103412X012
Application Information
The Control Selector function block is ideal for providing automatic override control. This function block can take three
control signals as input. The user can select SEL_TYPE = Low, Medium, or High for various control configurations.
Figure E‐8. Control Selector Function Block Diagram Example
AI
OUT
Function
Block
Flow Controller
IN
PID
Function
Block
Pressure Controller
PID
Function
IN
Block
AI
Function
Block
BKCAL_IN
BKCAL_IN
In the image shown in figure E‐9, a Fuzzy Logic Control (FLC) block is connected to a Control Selector block. Unlike the
PID block that uses a positional control equation, the FLC block uses a velocity control equation and can cause output
runaway on all blocks connected to a Control Selector block if a downstream block is limited. To prevent output
runaway, put a Filter block on the BKCAL wire between the Control Selector block and the FLC block. For modules
executing at one second, set the Filter block's TIMECONST parameter to 3 seconds.
BKCAL_IN
OUT
SEL_1
Control
Selector
Function
SEL_2
Block
OUT
OUT
BKCAL_SEL_2
BKCAL_SEL_1
BKCAL_OUT
OUT
AO
Function
CAS_IN
Block
DVC6200f Digital Valve Controller
CSEL Function Block
February 2017
247