Post on 03-Apr-2018
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1. Oscillator
2. Photoelectric emitter
3. Photoelectric receiver
4. Preamplifier
5. Logic Operations
6. Pulse/Level
7.Switching status display
8.Output stage with protective circuit9.External Voltage
10.Internal constant voltage supply
11.Optical switching distance
12.Switch output
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Optical Sensors
Red and Infrared light is used.
Emitter (LED) and Receiver. (photodiode
and phototransistor)
Objected may be reflective, matt,
opaque.high proportion of light to be
reflected directly or diffusely.
Operating switching distance varied by
potentiometer.
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Optical Sensors
Receiver is tuned to pulse of the emitter.
Emitter:
Without fiber optic-800nm (non visible,infrared)
With fiber optic 660nm
Single fiber optic 20,000
Built in protective measures (reversepolarity protection, Sc protection outputs,voltage peaks)
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Optical Sensors
Through Beam Diffuse
Retro reflective
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Through beam
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Through beam
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Through beam
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Through beam
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Through beam
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Through beam
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Through beam
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Response of through beam
sensors
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Advantages
Enhanced reliability because of permanent
light during non operation.
Wide range
Small objects can be detected at large
distances.
Good positioning accuracy
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Disadvantages
Two separate proximity sensor modules
(emitter and receiver) and separate
electrical connections are required,
Cannot be used for completely transparent
objects.
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Retro reflective
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Retro reflective
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Retro reflective
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Retro reflective
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Retro reflective
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Response of retro reflective
sensors
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Advantages:
Enhanced reliability because of permanent
light during non-operation.
Simple installation and adjustment.
Greater range in comparison with diffuse
sensors.
Only passive reflector is required on oneside of the conveyor without the need of
electrical cabling for receiver.
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Disadvantages:
Transparent, very bright or shiny objects
may remain undetected.
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Diffuse Sensor
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Diffuse Sensor
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Diffuse sensor
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Response range of diffuse sensor
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Advantages
Reflection on the object activates the
receiver, an additional reflector is not
required.
With through beam sensors objects can
only be detected laterally to the light
beam, diffuse sensors allow frontal
detection.
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Disadvantages
Response curve is not straight
Diffuse sensors are not suitable as
through beam sensors, if accurate lateral
response is crucial.
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Optical Sensors with fiber optic
cables
Fiber optic cables adapters are used if
conventional devices take up too much
room, areas with hazard.
Advantages: Position of small objects can
be detected with high accuracy.
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Advantages of fiber optic cables
Detection of objects in areas of restricted
access.
Possibility of remote installation of
proximity sensor housing.
Accurate detection of small objects.
Sensing elements can be moved.
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Advantages of polymer fiber optic
cables
Mechanically stronger than fiber glass.
Length can be reduced easily by cutting
the ends on the proximity sensors with a
sharp knife.
Cost saving.
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Advantages of glass fiber optic
cables
Suitable for high temperature.
Reduced optical attenuation with large
distances as well as at close infrared
range.
Longer lasting.
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