Watlow Controller Series D8, Руководство пользователя

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D8 Series User’s Guide
Chapter 4: Operation and Setup
81
Using cascade control, the outer thermocouple is used on the primary loop (in this example,
loop 1), and the inner thermocouple is used on the secondary loop (loop 2). The heater is controlled
by loop 2.
As the temperature of the outer thermocouple drops from 150°F to 140°F, the set point of the
secondary loop should rise from 150 to 190°F.
Table 4.9 and Table 4.10 show the setup for this application.
D8
Water
Power
Controller
Loop 2 PID Output
Heater
Loop 1 Input
Process Variable
Loop 1: Primary Cascade Loop
Loop 2: Secondary Cascade Loop
Loop 2 Input
Process Variable
Outer T/C
Inner T/C
Figure 4.11
– Example Application Using Cascade Control
Table 4.9 – Parameter Settings for the Primary Loop in the Cascade Example
MENU PARAMETER VALUE COMMENT
(none)
Set point 150°F
Desired temperature at the inner
thermocouple.
Control Ht prop band 10
As the input drops 10°F, the output
increases to 100 percent.
Control Ht integral 0
Only proportional control is used.
Control Ht derivative 0
Only proportional control is used.
Table 4.10 – Parameter Settings for the Secondary Loop in the Cascade Example
MENU PARAMETER VALUE COMMENT
Cascade Cascade prim loop 1
Loop 1 is the primary loop.
Cascade Cascade low SP 150°F
When the primary loop’s output is 0 percent,
the secondary loop’s set point is 150°F.
Cascade Cascade high SP 190°F
When the primary loop output is 100
percent, the secondary loop set point
is 190°F.