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SC100/200 Series Function Block Application Manual EM-6460-C
4.3.7 NON-LINEAR PID CONTROL
Non-linear PID control is useful to deal with non-linearity problems typically found in pH process control.
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LOOP CONFIGURATION EXAMPLE: NEUTRALIZATION CONTROL
The titration curve around pH 7 with an extreme non-linearity is adjusted to provide a relatively constant gain over entire span
by decreasing control gain around the equivalence point by multiplying it with a coefficient.
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BLOCK DIAGRAM
neutralizer
pH
PV
PHIC
MV
pH
PV
PHIC
G02
deviation
Non-linear Gain,
Deadband
MV
NLN
G30
