SECTION 1
INTRODUCTION
d
In an industrial environment, relays and solid-state electronic devices are
used to provide the necessary control signals for control system
applications. A relay can be either an electro-mechanical device or a solid-
state electronic device that is “hardwired” to perform a particular function.
When the application in which an electro-mechanical device is used is
changed, the device must be modified (from normally closed to normally
open, for example). In the case of a “hardwired” device, it must be replaced
with one that is tailored to the application.
A programmable controller (PC) is a solid-state device that directly
replaces the relays and “hardwired” electronic circuitry. A programmable
controller can be quickly modified to adapt to a new or changed
application. Gould introduced programmable controllers in the late 1960’s.
The first user was the automobile industry. Programmable controllers
allowed them to avoid the time and expense of rewiring relay control
systems at model changeover. Since then, the use of programmable
controllers has expanded to cover a wide variety of industrial control
system applications. Typical control system applications include
machines used in cutting, grinding, and welding metals; equipment for
assembling, packaging, and testing components and finished products;
machinery for weighing, transferring, and otherwise handling materials;
and systems for processing chemicals and foods.
l-l
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
To Next Page
Loading...
