2.4.5 Feedback Handling
Feedback handling can be congured to work with
applications requiring advanced control, such as multiple
setpoints and multiple types of feedback (see Figure 2.16.
Three types of control are common:
Single zone, single setpoint
This control type is a basic feedback
conguration.
Setpoint 1 is added to any other reference (if any) and the
feedback signal is selected.
Multi-zone, single setpoint
This control type uses two or three feedback sensors but
only one setpoint. The feedback can be added, subtracted,
or averaged. In addition, the maximum or minimum value
can be used. Setpoint 1 is used exclusively in this congu-
ration.
Multi-zone, setpoint/feedback
The setpoint/feedback pair with the largest dierence
controls the speed of the adjustable frequency drive. The
maximum attempts to keep all zones at or below their
respective setpoints, while minimum attempts to keep all
zones at or above their respective setpoints.
Example
A 2-zone, 2-setpoint application. Zone 1 setpoint is 15 bar
and the feedback is 5.5 bar. Zone 2 setpoint is 4.4 bar and
the feedback is 4.6 bar. If maximum is selected, the zone 1
setpoint and feedback are sent to the PID controller, since
it has the smaller dierence (feedback is higher than
setpoint, resulting in a negative dierence). If minimum is
selected, the zone 2 setpoint and feedback is sent to the
PID controller, since it has the larger dierence (feedback is
lower than setpoint, resulting in a positive dierence).
Figure 2.16 Block Diagram of Feedback Signal Processing
Product Overview Design Guide
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