Introduction to Industrial Automation

Figure 1.5  Manually operated control devices that have two operational states.

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  Introduction to Industrial Automation

The operation of an industrial automation device in an industrial process is not independent 

of the operation of the rest of the devices in the same process. In all cases, there is a strong depen-

dence among all the utilized devices in the automation, as is also highlighted in the following 

example. Consider an industrial process of adding color to textile products like fibers or yarns, 

called “dyeing”, where (as shown in Figure 1.6) it is desired to have the following operation:

… IF the selector switch is in the “R” position AND by pressing the push button “ON”, 

the electric valve V

R

 opens AND motors M

1

 and M

2

 operate AND when the level sensor 

S

L

 produces an output signal the electric valve V

R

 closes AND simultaneously the motor 

M

0

 starts to operate AND IF, due to a fault, the motor M

1

 stops, THEN the motor M

2

 

also stops AND …

All the previous demands, which are being produced from the type of the industrial process, 

constitute a set of dependencies that, without their formal satisfaction, the production of the final 

product is not feasible. The devices from these five categories, which are indicated in Figure 1.3, 

with their dependencies and the rest of the purely mechanical parts of the integrated machines or 

processes constitute the overall industrial system. This industrial system needs proper automation 

in order for the whole operation to be executed with a minimization of human intervention. The 

control of the devices that are characterized as ON and OFF states is denoted as automation, and 

is being carried out by the utilization of automation circuits; while the control of the devices that 

are analog is denoted as process control, and is being carried out by the utilization of automatic 

control systems.