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Manual
00809-0500-4881
Figure 8-20: PID Function Block Diagram for Feedforward Control
A. Outlet temperature input
B. AI function block
C. PID function block
D. AO function block
E. Out
F. Inlet temperature input
Cascade control with master and slave loops
Situation
A slave loop is added to a basic proportional/integral derivative (PID) control configuration
to measure and control steam flow to the steam heater. Variations in the steam pressure
cause the temperature in the heat exchanger to change. The temperature variation will
later be sensed by TT101. The temperature controller modifies the valve position to
compensate for the steam pressure change. The process is slow and causes variations
in the product temperature.
Rosemount OCX8800C
Figure 8-21
illustrates the process instrumentation diagram.
F
Fieldbus
™
OUNDATION
April 2023
157
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