Watlow CLS200 - Manual (Page 191)

CLS200 Series User’s Guide Chapter 9:Troubleshooting and Reconfiguring
Doc.# 0600-3050-2000 Watlow Anafaze 175
Communications
Most communications problems are due to incorrect wiring
or incorrectly set communications parameters. Therefore,
when there is a problem, check the wiring and communica-
tions settings first. Verify the following:
• Communications port: Software must be configured to
use the communications port to which the controller is
connected.
• Software protocol: Set the controller to MOD (Modbus)
for AnaWin or WatView, ANA (Anafaze) for Anasoft or
Anascan.
• Controller address: Configure software to look for the
controller at the correct address. In a multiple-control-
ler installation, each controller must have a unique
address.
• Baud rate: Software and controller must be set the
same.
• Error checking (ANA protocol only): Software and con-
troller must be set the same (CRC or BCC).
• Hardware protocol: PC and controller must use the
same protocol, or a converter must be used. The con-
troller is typically configured for EIA/TIA-232 when it
is shipped. See Changing Communications on page
179 to change between EIA/TIA-232 and EIA/TIA-485.
To communicate with more than one controller, or
when more than 50 feet of cable is required, use EIA/
TIA-485. Even for a single controller, you may use
EIA/TIA-485 and an optically isolating converter to
eliminate ground loops.
• Converter: Make sure that the EIA/TIA-232-to-485
converter is powered, configured and wired correctly.
• Cables: Check continuity by placing a resistor across
each pair of wires and measuring the resistance with
an ohmmeter at the other end.
Ground Loops
Many PC communications ports have their common wires
connected to chassis ground. Once connected to the control-
ler, this can provide a path to ground for current from the
process that can enter the controller through a sensor (such
as a thermocouple). This creates a ground loop that can af-
fect communications and other controller functions. To
eliminate a ground loop, either use an optically isolated
communications adapter or take measures to ensure that
sensors and all other connections to the controller are iso-
lated and not conducting current into the unit.