Eff. direction of the [Control], bidirectional or monodirectional
You can vary the
[control]
based on various features.
Function: A bidirectional
[control]
operates in two possible directions (increase AND decrease meas‐
ured value).
Application: Acidic or alkaline waste water is produced alternately in a neutralisation process in an
industrial waste water system. Before the water can be fed into the sewerage system, the pH value
must be set, for example, to a value between pH 6.8 and 7.5. A bidirectional controller with two
metering pumps for metering acid and alkali is used for this purpose. The pH value can be both
decreased or increased to come within the necessary setpoint range.
Measured value
Setpoint
Control variable
Negative
deviation
Negative
Control variable
Time
Time
Positive
Control variable
Positive
deviation
A1471
Fig. 83: Control type PID bidirectional. Control characteristic without dead zone
Setting the
[Control]
124
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