Description
Original instructions
About us
Function description
The function block forms a two-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 TWOPOINT_CON1 has the following properties:
Representation in FBD
Representation:
Representation in LD
Representation:
Representation in IL
Representation: 
CAL TWOPOINT_CON1_Instance (MAN:=ManualMode, 
    HALT:=HaltMode,SP:=SetPointInput, PV:=ProcessVariable, 
    K:=FeedbackGain, LAG_NEG:=RapidFeedbackTimeConstant, 
    LAG_POS:=SlowFeedbackTimeConstant, 
    DB:=HysteresisOfTwoPosSwitch,  
    XF_MAN:=FeedbackResetValue, 
    YMAN:=ManualValueForERR_EFF, Y=>OutputControlFlag, 
    ERR_EFF=>EffectiveError)
Representation in ST
Representation: 
TWOPOINT_CON1_Instance (MAN:=ManualMode, 
    HALT:=HaltMode,SP:=SetPointInput, PV:=ProcessVariable, 
    K:=FeedbackGain, LAG_NEG:=RapidFeedbackTimeConstant, 
    LAG_POS:=SlowFeedbackTimeConstant, 
    DB:=HysteresisOfTwoPosSwitch,  
    XF_MAN:=FeedbackResetValue, 
    YMAN:=ManualValueForERR_EFF, Y=>OutputControlFlag, 
    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
K
REAL
Feedback boost
LAG_NEG
TIME
Time constants of the quick feedback
LAG_POS
TIME
Time constants of the slow feedback
DB
REAL
Hysteresis from two point switch
XF_MAN
REAL
Reset value of the feedback in % (0 – 100)
YMAN
BOOL
"1" = Handwert für ERR_EFF
Description of output parameters:
Parameter
Data type
Description
Y
BOOL
"1" = Output manipulated variable
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 < 0 or XF_MAN > 100
the controller operates without internal feedback paths.
NOTE: For a list of all block error codes and values, see CLC.