Watlow Series D8 - Manual (Page 121)

Series D8 User’s Guide Chapter 4: Operation and Setup
Doc. 0600-3120-2000 Watlow Anafaze 103
Figure 4.11 Example Application Using
Cascade Control
Table 4.9 Parameter Settings for the Primary
Loop in the Cascade Example
Table 4.10 Parameter Settings for the Second-
ary Loop in the Cascade Example
As the temperature in the middle of the tank (loop 1) drops,
the output goes up proportionally and the set point of loop 2
goes up proportionally. Thus heat is added to the system at the
element even though the temperature near the element may
have been at the desired temperature.
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.
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 channel set point is 190° F.
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