Watlow PPC-2000 - Manual (Page 136)

Chapter 3: Operating with AnaWin 3 PPC-2000 User’s Guide
112 Watlow Anafaze Doc.# 30002-00 Rev 2.3
Differential Control
Differential control is a special case of ratio control. With
differential control, as with ratio, the set point of one channel
is determined by the process variable value of another channel.
The set point of the differential channel is calculated by adding
an offset (Set Point Offset) to the process variable value of the
master channel. The Set Point Ratio parameter is set to 1.
Remote Set Point
Remote set point is implemented in the PPC as a special case
of ratio control. As with ratio control, the set point of a channel
is set by multiplying an analog input value by a ratio (Set Point
Ratio) and adding an offset (Set Point Offset). Typically, however,
the analog input is not used as feedback for closed-loop control,
so there is no master channel. The Max Set Point and Min Set Point
parameters may be used to limit the set point value. Setup
remote set point according to the instructions for ratio control.
Logic Programs
The PPC-2000 is able to run not only the closed-loop control
program but also a user-written logic program. LogicPro is a
software program that runs under Windows95/98/NT. This
logic programming tool can be used to customize the function of
the PPC-2000 controller. Any of the digital and analog I/O as
well as all of the controller parameters can be accessed and
changed by user written logic programs. Logic programs are
stored along with the controller firmware in nonvolatile
memory. Consult the LogicPro User’s Guide for specific
instructions on how to write, compile and download logic
programs to the PPC-2000.
NOTE! If an output variable in a logic program sets a value
using an IO Driver and IO Physical Address, the
associated register in the PPC-2000 cannot be written
to by the closed-loop control program, an HMI or any
other device.