Watlow Series 988 - Manual (Page 143)

9.6 WATLOW Series 988 User’s Manual Enhanced Software Features, Chapter 9
Enhanced Software
Differential
Requirements
Two inputs and the enhanced software option are required.
Overview
Differential control allows the Series 988 to control one process at a differ-
ence to another process. Input 2 acts as a remote set point input. However
the displayed set point indicates the desired difference between input 1
and input 2. The set point that input 1 will use is determined by the equa-
tion:
internal set point = input 2 + differential set point
The lower display shows the differential set point, which can be adjusted
with the increment (up-arrow) and decrement (down-arrow) keys.
Please note that while in the differential control mode the internal set
point for input 1 cannot be viewed and must be calculated with the equa-
tion.