CLS200 Series User’s Guide
Chapter 5: Enhanced Features
105
Cool Span
Enter the multiplier to apply to the primary loop cool out-put percentage.
ALARM
02 CASCADE
CL SPAN? +9999
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 element. The desired
temperature of the water is 150°F, which is measured at the outer thermocouple. 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 with a
setpoint range of 150 to 190°F.
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
Figure 5.5
— Application Using Cascade Control
To set up this application, you would do the following:
1. Change the display to loop 2, which will be the secondary loop, and then enter the three-key
sequence (
ENTER
, then
ALARM ACK
, then
CHNG SP
) and go to the first screen in
Table 5.2
.
2. Follow the steps in
Table 5.2
to configure cascade control.
