This function block checks the value of process error (difference between set point and actual value). If the process error is positive and greater than the upper threshold value rOutOn, it calculates the control output as below,
q_rOput = Process error x rGain + rOfst
If the process error decreases below the lower threshold value rOutOff, it resets the control output to zero.
Similarly if process error is negative, and its absolute value is more than upper threshold value rOutOn, it calculates the control output as below,
q_rOput = Process error x rGain - rOfst
q_rOput is reset to zero if absolute value of process error becomes less than lower threshold value rOutOff.
The function block output is set manually as according to the value of input pin i_rManVa:.
|
IF |
AND IF |
THEN |
|---|---|---|
|
Abs(i_rManVal) < 1 |
- |
q_rOput = 0.0 |
|
Abs(i_rManVal) >= 1 |
rE > 0 |
q_rOput = rE x rGain + rOfst |
|
Abs(i_rManVal) >= 1 |
rE < 0 |
q_rOput = rE x rGain - rOfst |
|
Abs(i_rManVal) >= 1 |
rE = 0 |
q_rOput = 0.0 |
|
rE = i_rSp - i_rActVal Abs() Absolute value function. |
||
This figure shows the transfer function for the FB_3points_Ext function block:
This figure shows the timing diagram for the FB_3points_Ext function block:
An invalid parameter at the function block input results in a detected error state and a corresponding detected error ID is generated.
During the error detected state the output values are set to zero. Detected error can be reset only through rising edge of i_xErrRst input.
The output q_xBusy is TRUE whenever the function block is enabled and when there is no detected error.
