Page 179 - Sensors and Control Systems in Manufacturing

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FIGURE 3.11 Proximity detection.

FIGURE 3.12 Focused proximity sensor.

Background objects will not false-trigger a focused proximity sensor
since they are “cross-eyed” and cannot see past a certain point.
Advantages of the focused proximity sensor are:

• Its installation and alignment are simple. The control circuit
can be wired through only one side of the sensing zone.
• It can detect differences in surface reflectivity.

It also has certain limitations:
• It has a limited sensing range.
• The light/dark contrast and sensing range depend on the
target object’s surface reflectivity.
3.1.6 Automated Guided Vehicle System
The wide sensing field of diffuse reflective photoelectric sensors
makes them ideally suited for use as obstacle detection sensors. Sens-
ing distance and field width are adjustable to form the obstacle detec-
tion zone vital for manufacturing operations.
Two outputs, near and far, provide switching at two separate
sensing distances that are set by corresponding potentiometers.