Endress+Hauser Mycom S CLM 153 Operating Instructions Manual page 57

Mycom S CLM 153
Endress+Hauser
Range-dependent modulation gain
In contrast to normal PID controllers, with Mycom S you have the option of setting a
range-dependent modulation gain in addition to a constant controller gain. With range-
dependent gain, the controller gain used depends on the "range", i.e. on the present
actual value.
Areas of application for range-dependent gain are:
• Compensation of non-linearities:
The conductivity process is no longer linear at medium and high concentrations
(approx. > 15 %).
• For critical control systems,
you need a control which works very carefully near the setpoint and doses very
powerfully in the event of large control difference. If constant controller gain cannot do
this to your satisfaction, then you can achieve this by using range-dependent
modulation gain.
Yp(X)
100 %
0 %
-100 %
BaseFull BaseTentative
Fig. 22: Diagram to describe the most important corner points for control
With such a range-dependent characteristic, a set actuating variable is prescribed to
the controller for each measured 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 measured
value history.
X too low X too big
⇒ dosing ⇒ dosing
base acid
BaseNeutral SetPoint AcidNeutral
6 Commissioning
X
AcidTentative AcidFull
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