Watlow PPC-2000 - Manual (Page 61)

PPC-2000 User’s Guide Chapter 2: Hardware Installation
Doc.# 30002-00 Rev 2.3 Watlow Anafaze 37
• You can use other voltage suppression devices, but they
are not usually required. For instance, you can place a
metal oxide varistor (MOV) rated at 130Vac for 120Vac
control circuits across the load, which limits the peak AC
voltage to about 180Vac. You can also place a transorb
(back to back zener diodes) across the digital output,
which limits the digital output voltage.
The above steps will eliminate most EMI/RFI noise problems.
If you have further problems or questions, please contact
Watlow Anafaze.
Avoiding Ground Loops
Ground Loops can cause instrument errors or malfunctions. Do
not connect any of the following pins to each other or to earth
ground:
• DC power common terminals on the PPC power supply
and PPC-2010 Processor Module
• DC common terminals on TB50s
• Analog common terminals on AITBs
• Signal common terminals on the EITB or other devices
connected to the encoder inputs on a PPC-2030
Watlow Anafaze strongly recommends that you:
• Isolate outputs through solid state relays, where possible.
• Isolate RTDs or “bridge” type inputs from ground.
Connecting I/O to the PPC-2010
A TB50 connects to the PPC-2010 Processor module through
the 50 pin SCSI connector. Refer to Figure 2.20 on page 38. The
terminal block interfaces to field wiring of the digital I/O
(sensors, actuators, relays, SSRs, etc.).
Connecting the TB50 to the PPC-2010 Module
Refer to Figure 2.20 on page 38. Connect the SCSI connector
from the PPC-2010 module to the TB50.