CD600 Plus - User's Manual
4.22
FACTOR G
1.0
0.8
0.6
0.4
0.2
50%
100%
LEVEL
Fig 4.9.7 - Gain Curve as a Function of PV
While planning the configuration, observe the following:
It is not necessary to use all 13 points of the curve.
It is fundamental to use the 0% and the 100% of the determining variable (-100 and +100% for the
Error).
It is recommendable to program the variable up to 102%, since the variable may be above 100%.
4. Tuning is normally done for G = 1. In the example, the control becomes slower above or below
50% of the level.
Adaptative Gain is also very useful for pH control.
ANTIRESET-WINDUP (CARL AND CARU)
The control algorithm automatically stops the contribution of the integral mode when the output
signal reaches the limits of 0 or 100%. Contributions of the Proportional and Derivative modes are
not affected.
The CD600 has a unique feature: the adjustment of the limits for the integral mode saturation.
It is normally fixed at 0% (CARL) and 100% (CARU), but can be narrowed, allowing quicker
responses and avoiding overshoot in heating processes, for example.
PID CONSTANTS (AKp, ATr, ATd)
The table is self-explanatory. It is good to remember that the Proportional action is in terms of Gain
and not of Proportional Band. Bigger Kp means more action. The Integral action is in terms of
minutes per repeats, not repeats per minute. Smaller T
R
means more Integral action.
PID constants may be adjusted by the Hand Held Programmer or the controller's front panel (see
tuning procedures). In order to inhibit tuning by the front panel, simply configure parameter CACT
(action) with 2, 3, 6 or 7 instead of 0, 1, 4 or 5.
DEVIATION ALARM (AMXD, ATOD)
These parameters establish the alarm limit for the control deviation or error (AMXD) and for how
long this deviation may be tolerated without alarm activation (ATOD).
If AMXD=5 and ATOD=0.5, the block will set the "Dev-time-out" output to high logic level if a
5% deviation or more persists for more than 0.5 minutes. Note that 0.00 for the time is here
considered as infinite time or no alarm. The shortest time available is 0.01 minute.
CFRT specifies if the deviation alarm should appear on the front panel or not.
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