Watlow CLS200 - Manual (Page 142)

Chapter 6: Enhanced Features CLS200 Series User’s Guide
126 Watlow Anafaze Doc.# 0600-3050-2000
for a higher setpoint. This value is expressed in the same
engineering units as the ratio loop’s process variable.
Selectable values: Any value from the minimum value of
the ratio loop’s process variable to its maximum value.
Control Ratio
Enter the multiplier to apply to the master loop’s process
variable.
Selectable values: 0.1 to 999.9.
Setpoint Differential
Enter the value to add or subtract from the ratio loop set-
point calculation before using it as the setpoint. This value
is expressed in the same engineering units as the ratio
loop’s process variable.
Selectable values: -9999 to 9999 with the decimal
placement determined by the DISP FORMAT setting for the
ratio loop.
Ratio Control Example: Diluting KOH
A chemical process requires a formula of two parts water
(H
2
O) to one part potassium hydroxide (KOH) to produce
diluted potassium hydroxide. The desired flow of H
2
O is 10
gallons per second (gps), so the KOH should flow at 5 gps.
Separate pipes for each chemical feed a common pipe. The
flow rate of each feeder pipe is measured by a CLS200, with
H
2
O flow as process variable 1 and KOH flow as process
variable 2. The outputs of loops 1 and 2 adjust motorized
valves.
ALARM
02 RATIO CONTROL
MAX SP? 25
ALARM
02 RATIO CONTROL
CTRL RATIO? 1.0
ALARM
02 RATIO CONTROL
SP DIFF? 0