The Photo electric sensor can be used to detect both metallic and non metallic targets. The main components of a photo electric sensor are the emitter and detector.
The emitter sends a beam of light which is then detected by detector.
Photoelectric sensors works in different modes
Thru-Beam: In this case the emitter and detector are 2 separate units. The emitter emits the light which is detected by the detector. A target is detected when it passes in-between the emitter and detector.
The emitter sends a beam of light which is then detected by detector.
Photoelectric sensors works in different modes
Thru-Beam: In this case the emitter and detector are 2 separate units. The emitter emits the light which is detected by the detector. A target is detected when it passes in-between the emitter and detector.
The advantages of this mode is that the sensing range is moreThe disadvantage is 2 parts need to be mounted separately and for long range the installation could be difficult because the emitter has to be put with the detection range of the detector.
Diffuse Reflective: In this case the emitter and detector are put in the single package in such a way that their field of view cross. Here the emitter continuously emits the light. When the target comes within the operating range of the sensor the light from the emitter is reflected off the target and detected by the detector.
The advantages of this are low cost, easy installationThe disadvantages are short sensing distance. The sensing distance depends on target size, surface and shape.
Retro-Reflective: the main components of this sensor are the emitter, detector and the Retro-reflector. The emitter and the detector are in the same package. The Retro-reflector is placed little far from the sensor. The light from the emitter is reflected off the Retro-reflector and detected by the detector. When the target passes between the sensor and the Retro-reflector the beam is not reflected back to the detector. Here the problem can be that the beam could reflect from the target itself. For this the polarising filter is used in the sensor. Hence only the light reflected by the retro-reflector is detected by detector
The advantages of this are low cost and easy to install
The disadvantages are separate retro-reflector to be used, Cannot be used to detect small objects as the target has to block the entire beam from emitter, performance could be affected in case of dirt on retro-reflector, problems in detecting clear targets
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