INFICON SQM-242 Thin Film Deposition Controller Card Software Operating Manual - Manual (Page 13)

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SQS-242 Operating Manual
1.3 Digital I/O
Digital I/O for the SQS-242 software can be provided through an inexpensive,
external, programmable logic controller (PLC), see
Figure 1-3 . This allows the
PLC, and the associated I/O wiring, to be placed in a convenient location in a wiring
cabinet. A single, serial communications cable runs to the computer. The PLC
provides electrical isolation, fail-safe operation, and extensive I/O processing
capabilities through its ladder logic programming.
Figure 1-3 Programmable Logic Controller (PLC)