are frequently employed to sense an object's presence because they are easy to use.
An RLS differs from other light sensors in that the target does not simply break a light beam but reflects light to a detector.
Through the years, RLSs have been refined so that they are less sensitive to ambient light and can detect minute or transparent objects. Some devices can even determine the distance between sensor and object, thereby offering an alternative to ultrasonic systems.
While in general, RLSs are becoming smaller, two divergent trends are emerging as well. One group of sensors is becoming simpler, basically containing only a light source and detector. Sensor output is a simple on/off signal, and users provide the power supply and signal processing circuitry.
The other group is becoming full featured. These devices contain a power supply and logic. Users program the device by setting switches or with a PC.
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