Fisher FIELDVUEDVC6200f Instruction Manual page 248

DVC6200f Digital Valve Controller
CSEL Function Block
February 2017
Figure E‐9. FLC block Connected to a Control Selector Block
AI
OUT
Function
Block
Flow Controller
IN
FLC
Function
Block
Pressure Controller
PID
Function
IN
Block
AI
Function
Block
BKCAL_IN
OUT
BKCAL_IN
Use the Control Selector function block in a situation where flow is the primary control variable but pressure must be
controlled in the event that it rises to an unacceptable level. Figure E‐10 illustrates this example.
At normal operating pressures, the pressure PID's high SP requests a maximum valve opening to increase pressure.
The flow PID's signal is lower than that of the pressure PID. In this case, SEL_TYPE is set to Low so that the Control
Selector function block sends the flow PID's signal on to the supply valve and blocks the pressure PID's signal.
If the flow stream's pressure rises to an unacceptable level, the pressure PID sends a low signal to the supply valve,
telling it to close. When this output signal falls below that from the flow PID, the Control Selector function block
begins to pass the pressure PID's signal and block the flow PID's signal.
248
BKCAL_IN
OUT
SEL_1
Control
Selector
Function
SEL_2
Block
OUT
OUT
BKCAL_SEL_2
Filter
IN
Function
Block BKCAL_SEL_1
BKCAL_OUT
OUT
AO
Function
CAS_IN
Block
Instruction Manual
D103412X012