
1/03 UDC 6300 Process Controller Product Manual 175
5.11 2 Loops of Control Overview, Continued
Internal Cascade
Figure 5-4 is a Block Diagram of Internal Cascade for a 2 Loop controller.
Figure 5-4 Functional Overview Block Diagram of Internal Cascade of a 2 Loop Controller
Remote Setpoint
Local Setpoint
SP 1
SP 2
SP 3
PID
CONTROL
ALGORITHM
Loop 2
OUTPUT
To Final
Control
Element
PV SOURCE
See Loop 2
Block Diagram
PRIMARY LOOP
PV SOURCE
See Loop 1
Block Diagram
SECONDARY LOOP
PID
CONTROL
ALGORITHM
Loop 1
SETPOINT
SOURCE
Loop #1
INTERNAL
OUTPUT
SIGNAL
SETPOINT
SOURCE
See Loop #2
Block Diagram
INTERNAL CASCADE RULES
• Loop #2 must be the primary loop.
• Loop #1 must be the secondary (internal or slave) loop because all output forms exist on Loop 1.
• Loop #1 Remote Setpoint is fixed as loop #2 output.
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