Endress+Hauser Mycom S CPM 153 Operating Instructions Manual page 59

Mycom S CPM 153
Endress+Hauser
Kp(X)
100 %
0 %
-100 %
BaseFull BaseTentative
Fig. 22: Diagram to describe the most important corner points for control
With this characteristic, a reference set value is prescribed to the controller for each pH
value.
Neutral zone:
If the actual value (X) is within the neutral zone, then
• the dosing does not take place for the Batch process type,
• also not for the Inline process type and without an I component (Tn=0).
• If the controller is configured as a PI or PID controller for the Inline type, the controller
decides itself if dosing will be carried out or not. This is dependent on the
pH value history.
Points of the characteristic:
For constant control gain ("linear characteristic"), you require:
Set point W,
Neutral zone
– Two-sided: "Start of the neutral zone" and "End of neutral zone"
– One-sided: only one of the two points
For range-dependent modulation gain ("segmented curve"), you require two-sided con-
trol of all the points.
A point usually consists of two coordinates: an x coordinate (here = pH-value) and a y
coordinate (here = set value). You only need enter the y coordinates for the optimisation
points. For the other points, the CPM 153 sets the y coordinates itself.
However, you cannot change the sequence of these defined points. It is, for example,
not possible to enter a larger pH value for the "Start of the neutral zone" than for the set
point.
Configuring the CPM 153
Sequence:
1. Actuators
2. Sensor technology
3. Feedback (e.g. look-ahead pH measurement, position feedback with three-point
step controller, if available)
4. Curve:
In the user settings (see below) you switch directly to an active measuring menu and
can check the settings made and change them if necessary.
X too low X too big
⇒ dosing ⇒ dosing
base acid
BaseNeutral SetPoint AcidNeutral
6 Start-up
X
AcidTentative AcidFull
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