Introduction to Industrial Automation

Figure 2.53  Random pressure variation and NC switch-contact differential behavior of a pres-

sure switch (a) and a non-differential piston type pressure switch (b).

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  Introduction to Industrial Automation

It should be clear to the reader that, concerning the characteristics of various industrial sen-

sors, a minimum representative set of sensor types and detecting methods have been covered in 

Chapter 2, since there are hundreds of other kinds and types of sensors for all physical quantities 

and it is beyond the scope of this book to provide a complete list of these sensors (e.g., optical 

laser sensors for the detection of very small objects, fiber optic sensors using optical fiber as 

sensing element, linear position sensors based on the magnetostrictive technology, piezoelectric 

accelerometers for sensing vibration, inclination sensors, and vibrating level switches). Even with 

this huge variety in industrial sensors, all of them participate in an automation system in exactly 

the same way, which is the insertion of their digital or analog output into the process controller, 

which is described in Chapters 3 and 4. The industrial engineer should be in a position to have 

a comprehensive overview of the sensing elements, as well as be aware of the current trends and 

new, upcoming sensing devices, in order to select the best sensing technologies for a specific 

application; a selection that should satisfy both the performance requirements, as well as the cost 

constraints.