Watlow CPC400 - Manual (Page 89)

CPC400 Series User’s Guide Chapter 3: Operation and Setup
Doc. 0600-2900-2000 Watlow Anafaze 75
Figure 3.14 Application Using Ratio Control
Table 3.12 Ratio Control Settings for the Ratio
Loop (Loop 2) in the Example
Setting Up Differential Control
Differential control is a simple application of ratio control,
used to control one process (ratio loop) at a differential, or
offset, to another process (master loop).
How to Set Up Differential Control
Set up differential control as you would set up ratio control.
Set the Control ratio parameter to 1.0, and enter the de-
sired set point differential (offset) at the Ratio SP diff pa-
rameter.
Menu Parameter Value Comment
Ratio Ratio master loop 01 Loop 1 is the master loop.
Ratio Ratio low SP 0.0
The minimum ratio loop set point is 0.0 gallons
per second (gps).
Ratio Ratio high SP 7.0 The maximum ratio loop set point is 7.0 gps.
Ratio Control ratio 0.5
The H
2
0 flow rate (10 gps) is multiplied by 0.5
to obtain the KOH flow rate (5 gps).
Ratio Ratio SP diff 0 For this example, there is no set point differential.
CPC400
Loop 1 PID Output
Loop 2 PID Output
Loop 1 Input
Process Variable
Loop 2 Input
Process Variable
Motorized Control Valve 2 Motorized
Control
Valve 1
Mixture Output
Water Input KOH Input
Flow
Transducer
Loop 1: Water Flow Control Loop
Loop 2: KOH Flow Control Loop
Serial
DAC
Serial
DAC