Setting Up Differential Control; How To Set Up Differential Control; Figure 4.14 - Application Using Ratio Control; Table 4.11 - Ratio Control Settings For The Ratio Loop (Loop 2) In The Example - Watlow D8 Series User Manual

D8 Series User's Guide
Chapter 4: Operation and Setup
Figure 4.14 – Application Using Ratio Control
Table 4.11 – 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 desired set point differential (offset) at the Ratio SP diff parameter.
KOH Input
Water Input
Flow
Transducer
Motorized
Control
Valve 1
Mixture Output
MENU PARAMETER
Ratio Ratio master loop
Ratio Ratio low SP
Ratio Ratio high SP
Ratio Control ratio
Ratio Ratio SP diff
Loop 1: Water Flow Control Loop
Loop 2: KOH Flow Control Loop
Loop 1 Input
Process Variable
D8
Loop 2 Input
Process Variable
Motorized Control Valve 2
VALUE
01
0.0
7.0
0.5
0
Loop 1 PID Output
Loop 2 PID Output
COMMENT
Loop 1 is the master loop.
The minimum ratio loop set point is
0.0 gallons per second (GPS).
The maximum ratio loop set point is
7.0 GPS.
The H 0 flow rate (10 GPS) is multiplied by
2
0.5 to obtain the KOH flow rate (5 GPS).
For this example, there is no set point
differential.
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