Page 172 - Sensors and Control Systems in Manufacturing

CHAPTER 3

Fiber Optics

in Sensors and

Control Systems

3.0 Introduction
Accurate position sensing is crucial to automated motion control sys-
tems in manufacturing. The most common components used for
position sensing are photoelectric sensors, inductive proximity sen-
sors, and limit switches. They offer a variety of options for manufac-
turing implementation from which highly accurate and reliable
systems can be created. Each option has its features, advantages, and
disadvantages that manufacturing personnel should understand for
proper application. Three types of sensors are used in manufacturing
applications:
• Photoelectric sensors. Long-distance detection.
• Inductive proximity sensors. Noncontact metal detection.
• Limit switches. Detection with traditional reliability.

3.1 Photoelectric Sensors—Long-Distance Detection
A photoelectric sensor is a switch that is turned on and off by the
presence or absence of receiving light (Fig. 3.1). The basic components
of a photoelectric sensor are a power supply, a light source, a photo-
detector, and an output device. The key is the photodetector, which is
made of silicon, a semiconductor material that conducts current in
the presence of light. This property is used to control a variety of out-
put devices vital for manufacturing operation and control, such as
mechanical relays, triacs, and transistors, which in turn control
machinery.

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