Watlow CLS200 - Manual (Page 137)

CLS200 Series User’s Guide Chapter 6: Enhanced Features
Doc.# 0600-3050-2000 Watlow Anafaze 121
Heat Span
Enter the multiplier to apply to the primary loop heat out-
put percentage.
Selectable values: -9999 to +9999.
Cool Span
Enter the multiplier to apply to the primary loop cool out-
put percentage.
Selectable values: -9999 to +9999.
Cascade Control Example: Water Tank
A tank of water has an inner and outer thermocouple. The
outer thermocouple is located in the center of the water.
The inner thermocouple is located near the heating ele-
ment. The desired temperature of the water is 150˚ F,
which is measured at the outer thermocouple. Using cas-
cade 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 con-
trolled by loop 2 with a setpoint range of 150 to 190˚ F.
Figure 6.5 Application Using Cascade
Control
ALARM
02 CASCADE
HT SPAN? +9999
ALARM
02 CASCADE
CL SPAN? +9999
CLS200
Water
150 °
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
Thermocouple
Inner Thermocouple