Watlow PM PLUS 6 - Example 5: Differential

Watlow PM PLUS™ 6 • 108 • Chapter 9: Applications
Example 5: Differential
Requirements: Two analog inputs and the enhanced software option are required and at least one output adjusts
the controlled part of the process.
Overview: Differential control maintains one process at a difference to another process. When function is set for
Differential, the PV Function output equals Source A minus Source B. Control loop 1 will control Analog Input 1
difference to Analog Input 2 based on Set Point 1.
Ratio
Set Point 1
Function
Filter
Source A
Source A
Source B
Heat Power
Cool Power
0 to 100%
0 to 100%
Output
Heat
Cool
Output n
Output n
Analog Input 1
Analog Input 2
Control Loop 1
PV Function
controlled
uncontrolled
Input 1
Input 2
Output 1
Control Loop 1
Differential
Set Point 1
Function
Filter
Source A
Source A
Source B
Heat Power
Cool Power
0 to 100%
0 to 100%
Output
Analog Input 1
Analog Input 2
Heat
Cool
Output n
Output n
PV Function