Watlow PPC-2000 - Manual (Page 198)

Chapter 5: LogicPro and Modbus Reference PPC-2000 User’s Guide
172 Watlow Anafaze Doc.# 30002-00 Rev 2.3
Process Variable Low (PV Lo)
Set this register to the value to be displayed when the signal is
at the level set in Input Signal Low (see above). See Setting PV Lo
and PV Hi on page 99 for detailed information.
Process Variable High (PV Hi)
Set this register to the value to be displayed when the signal is
at the level set in Input Signal High (see above). See Setting PV Lo
and PV Hi on page 99 for detailed information.
PV Offset/Counter Reset
This value is added to the scaled input before it is entered in the
Input Value register for temperature sensor input types
(T/Cs and RTDs). For counter input types, when this register is
written to, the count is set equal to the value written. This can
be used to reset or pre-load counter values.
Channel Parameters in the Database
Channel parameters determine the behavior of the PPC’s 48
closed-loop control channels. Channels are not inherently
associated with any particular hardware I/O. The user
associates a channel with a particular input and output by
setting the Process Variable Source and the Output Destination
parameters.
Channel numbers are, therefore, selected at the users
discretion. Each channel does, however, have many parameters
associated with it. It is up to the user to make sure the channel
parameters are appropriate for closed-loop control.
Accessing Channel Parameters with Modbus
For channel parameters the Modbus address offsets correspond
to the channel numbers. (Note that channel numbers are not
affected by the analog input selected as the Process Variable
Source or the output selected as the Output Destination (Heat/Cool
Output Dest).)
For example, register addresses for Heat Proportional Band (Heat
Prop Band) for channels 1-48 are 43101 to 43148. Channel 1’s
Heat Proportional Band is stored at address 43101. Channel 2’s
Heat Proportional Band is stored at address 43102, and so on.
Table 5.12 on page 174 lists first and last Modbus addresses for
each channel parameter. Use these addresses when accessing
channel parameters with third-party software or operator
interface terminals.