Watlow CLS - Manual (Page 167)

Appendix B: Enhanced Process Control
159
Now press the "Back" key several times until the normal loop display
appears. The setpoint of loop 2 will now be equal to the Input range of
Loop 1, which is 0-5 Vdc which is representative of the 0-300 ºF.
To complete the Remote SP setup, Loop 1 may be configured for
outputs and alarms. Likewise, Loop 2 must be configured for inputs,
outputs, and alarms.
Please consult the SETUP Section of this manual for information on
PID loop setup.
Differential Control
Differential Control is a simple application of the Ratio Control option,
used to control one process at a differential (or offset) to another.
A thermal forming application requires that the outside heaters operate
at a higher temperature than the center heaters. In some applications
these may be in bands of temperatures. The diferential control point is
determined by the Master channel which is using IR sensors for
temperture feedback. Secondary loops will be using T/Cs for feedback.
Enter the maximum Ratio loop SP. For
this example, we will use 300 ºF as a
maximum
Press Enter.
Enter the control ratio, which is the mul-
tiple applied to the master Process Vari-
able. In this example the ration is 1.0.
Press Enter.
Enter the setpoint differential (or offset).
For this example we have no offset
requirement and will use 0
Press Enter.
Display User Input
LOOP PROCESS UNITS
ALARM SETPOINT STATUS OUT%
02 RATIO CONTROL
MAX SP? 300
LOOP PROCESS UNITS
ALARM SETPOINT STATUS OUT%
02 RATIO CONTROL
CTRL: RATIO? 1.0
LOOP PROCESS UNITS
ALARM SETPOINT STATUS OUT%
02 RATIO CONTROL
SP DIFF.? 0