Description
Original instructions
About us
Function description
The function block represents a simple PI controller.
A system deviation ERR is formed by the difference between the reference variable SP and the controlled variable PV. This deviation ERR causes the manipulated variable Y to change.
NOTE: This function block performs an internal initialization in the first program cycle after a warm start or cold start (e.g. application download or power cycle) of the PLC program.
Due to this, you have to make sure that the function block is invoked in the first program cycle. In case of inkoving the function block in a later program cycle, the internal initialization will not be performed and the ouputs may deliver wrong values.
WARNING
UNEXPECTED OUTPUT BEHAVIOUR
Make sure that the function block is always invoked in the first program cycle.
Failure to follow these instructions can result in death, serious injury, or equipment damage.
EN and ENO can be configured as additional parameters.
Properties
The function block has the following properties:
Representation in FBD
Representation:
Representation in LD
Representation:
Representation in IL
Representation: 
CAL PI_Instance (SP:=SetpointInput, PV:=ProcessVariable, 
    MODE:=OperatingModes, PARA:=Parameter, 
    YMAN:=ManualManipulatedVariable, Y:=ManipulatedVariable, 
    ERR=>SystemDeviation, STATUS=>StatusOfOutput_Y)
Representation in ST
Representation: 
PI_Instance (SP:=SetpointInput, PV:=ProcessVariable, 
    MODE:=OperatingModes, PARA:=Parameter, 
    YMAN:=ManualManipulatedVariable, Y:=ManipulatedVariable, 
    ERR=>SystemDeviation, STATUS=>StatusOfOutput_Y) ;
PI parameter description
Description of input parameters:
Parameter
Data type
Description
SP
REAL
Setpoint input / reference variable
PV
REAL
Process variable / controlled variable
MODE
Mode_MH
Operating mode
PARA
Para_PI
Parameter
YMAN
REAL
Manual value
Description of input / output parameters:
Parameter
Data type
Description
Y
REAL
Manipulated variable
Description of output parameters:
Parameter
Data type
Description
ERR
REAL
System deviation
STATUS
Stat_MAXMIN
Y output status
Parameter description Mode_MH
Data structure description
Element
Data type
Description
man
BOOL
"1": Manual mode
halt
BOOL
"1": Halt mode
Parameter description Para_PI
Data structure description
Element
Data type
Description
gain
REAL
Proportional action coefficient (gain)
ti
TIME
Integral time
ymax
REAL
Upper limit
ymin
REAL
Lower limit
Parameter description Stat_MAXMIN
Data structure description
Element
Data type
Description
qmax
BOOL
"1" = Y has reached the upper control limit
qmin
BOOL
"1" = Y has reached the lower control limit
Runtime error
An error message is returned if
NOTE: For a list of all block error codes and values, see CLC_PRO.