You must automate a process, but you can't decide between a DCS
and a PLC. Are these systems really all that different? The
answers depend on a slew of other questions. turn the clock back
10 years: The programmable logic controller (PLC) is king of
machine control while the distributed control system (DCS)
dominates process control. If you manufacture plastic widgets,
you speak PLC. If you produce chemicals, you speak DCS. Today,
the two technologies share kingdoms as the functional lines
between them continue to blur. We now use each where the other
used to rule. However, PLCs still dominate high-speed machine
control, and DCSs prevail in complex continuous processes. The
early DCS looked dramatically different from the early PLC (Fig.
1, original article). Initially, the DCS performed the control
functions of the analog panel instruments it replaced, and its
interface mimicked their panel displays. DCSs then gained
sequence logic capabilities to control batch processes as well
as continuous ones. DCSs perf