Simatic 505 SoftShop
9 - PID Loops
••••
155
Monitor Low/High
Select Yes to have the controller monitor the Low/High Alarm;
otherwise, select No. The Low/High Loop can be entered as values
requiring remedial action.
Process Variable Alarm Low-Low
Enter a real number in engineering units; must be less than or equal to
low Alarm value, and greater than or equal to low range of Process
Variable.
Process Variable Alarm Low
Enter a real number in engineering units; must be less than or equal to
high Alarm value of Process Variable.
Process Variable Alarm High
Enter a real number in engineering units; must be less than or equal to
high-high Alarm value of Process Variable.
Process Variable Alarm High-High
Enter real number in engineering units; must be greater than or equal to
high Alarm value, and less than or equal to high range of Process
Variable.
Remote Setpoint
Select
NONE
if there is no remote setpoint. Otherwise, enter an address:
V, K, WX, WY, or LMN in the REMOTE SETPOINT field.
Clamp Setpoint Low/High
Enter values for the setpoint limits in the CLAMP SETPOINT LIMITS
field. If there are no limits, enter zeroes in the High and Low fields.
Loop Gain
Enter the value for the tuning constant LOOP GAIN in this field. See
Note 1 below.
Reset Time
Enter the value for the tuning constant Reset Time (INTEGRAL TIME)
in this field. See Note 1 below.
Rate Derivative Time
Enter the value for the tuning constant RATE DERIVATIVE TIME in
this field. See Note 1 below.
NOTE
It is not always necessary to have full three-mode PID control of
a loop. Parts of the PID equation can be eliminated by choosing
appropriate values for the gain (K
c
), reset (T
i
), and rate (T
d
), thus
yielding a P, PI, PD, I, and even an ID or a D loop. To eliminate
integra
l
action, set (T
i
) to infinity. To eliminate
derivative
action, set (T
d
) to zero.
To eliminate
proportional
action, set (K
c
) to zero.
