INFICON SQM-242 Thin Film Deposition Controller Card Software Operating Manual - Manual (Page 69)

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SQS-242 Operating Manual
Chapter 4
Digital I/O
4.1 Introduction
Digital I/O for the SQS-242 software can be handled by an inexpensive PLC. This
section will cover interfacing a Omron CPM2 series PLC to the SQS-242 card and
PC. It is not necessary, however, to use external I/O with the SQS-242 software.
There are several benefits to using an external PLC for I/O. First, noisy high voltage
wiring can be placed near the control sources, rather than routed into the
controller’s equipment rack. Only a single serial cable runs from the PLC to the
controller. The PLC also provides electrical isolation for the process controller. And
finally, the PLC’s ladder logic programming provides fail-safe process protection
and allows I/O to be easily tailored to each end user’s installation.
4.2 PLC Installation
CAUTION
The Omron PLC uses a special RS-232 cable as shown in
Figure 4-1 . Do not use a standard serial cable. Damage to
the PC or the PLC could result.
Figure 4-1 Omron PLC RS-232 Cable