Description
Original instructions
About us
Function description
The function block forms a three-point controller, which maintains PID-similar behavior through two dynamic feedback paths.
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 THREEPOINT_CON1 contains the following properties:
Representation in FBD
Representation:
Representation in LD
Representation:
Representation in IL
Representation: 
CAL THREEPOINT_CON1_Instance (MAN:=ManualMode, 
    HALT:=HaltMode,SP:=SetPointInput, 
    PV:=ProcessVariableInput, GAIN:=FeedbackGain, 
    LAG_NEG:=RapidFeedbackTimeConstant, 
    LAG_POS:=SlowFeedbackTimeConstant, 
    HYS:=HysteresisThreePositionSwitch, DB:=Deadband, 
    XF_MAN:=FeedbackResetFactor, 
    YMAN_POS:=ManualControlOutputForY_POS, 
    YMAN_NEG:=ManualControlOutputForY_NEG, 
    Y_POS=>PosManipulation, Y_NEG=>NegManipulation, 
    ERR_EFF=>EffectiveError)
Representation in ST
Representation: 
THREEPOINT_CON1_Instance (MAN:=ManualMode, 
    HALT:=HaltMode,SP:=SetPointInput, 
    PV:=ProcessVariableInput, GAIN:=FeedbackGain, 
    LAG_NEG:=RapidFeedbackTimeConstant, 
    LAG_POS:=SlowFeedbackTimeConstant, 
    HYS:=HysteresisThreePositionSwitch, DB:=Deadband, 
    XF_MAN:=FeedbackResetFactor, 
    YMAN_POS:=ManualControlOutputForY_POS, 
    YMAN_NEG:=ManualControlOutputForY_NEG, 
    Y_POS=>PosManipulation, Y_NEG=>NegManipulation, 
    ERR_EFF=>EffectiveError) ;
Parameter description
Description of input parameters:
Parameter
Data type
Description
MAN
BOOL
"1" = Manual operating mode
HALT
BOOL
"1" = Halt mode
SP
REAL
Setpoint input
PV
REAL
Actual value input
GAIN
REAL
Feedback gain (Feedback Parameter Set)
LAG_NEG
TIME
Time constant of the quick feedback (Feedback Parameter Set)
LAG_POS
TIME
Time constant of the slow feedback (Feedback Parameter Set)
HYS
REAL
Hysteresis from three point switch
DB
REAL
Dead zone
XF_MAN
REAL
Feedback path reset value in % (-100 to 100)
YMAN_POS
BOOL
Manual manipulation for Y_POS
YMAN_NEG
BOOL
Manual manipulation for Y_NEG
Description of output parameters:
Parameter
Data type
Description
Y_POS
BOOL
"1" = positive manipulated variable at output ERR_EFF
Y_NEG
BOOL
"1" = negative manipulated variable at output ERR_EFF
ERR_EFF
REAL
Effective switch value
Runtime error
With HYS > 2 * DB an error message is returned.
NOTE: For a list of all block error codes and values, see CLC.
Warning
In the following cases a warning will be returned:
If...
Then...
LAG_NEG = 0 and LAG_POS > 0
The controller works as if it had only a positive feedback with time constant LAG_POS.
LAG_POS < LAG_NEG > 0
The controller works as if it had only a negative feedback with time constant LAG_NEG.
XF_MAN < -100 or XF_MAN > 100
the controller operates without internal feedback paths.
NOTE: For a list of all block error codes and values, see CLC.