Optical - Diffuse

1. 17.10.03 No. 1 / 91© Festo Didactic – Training and Consulting Sensors
Optical - Diffuse
Inductive
Reed switch
Inductive magnetic
Capacitive
Symbols
Connection
Optical – Through-beam
Optical – Retro-reflective
Proximity sensors

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Type : Through-beam
Optical sensors (Through-beam)

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Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Targe
t
Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver

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Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Targe
t
Long sensing distance: up to 30 metres with some devices
Will detect all but very transparent materials
Must be accurately aligned
Transmitter Receiver
Type : Through-beam
Optical sensors (Through-beam)

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Optical sensors (Retro-reflective)

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Reflector
(prismatic)
T
R
Optical sensors (Retro-reflective)
Type : Retro reflective
Transmitter
/Receiver

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Reflector
(prismatic)
T
RTransmitter
/Receiver
Optical sensors (Retro-reflective)
Type : Retro reflective

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Reflector
(prismatic)
T
RTransmitter
/Receiver
Optical sensors (Retro-reflective)
Type : Retro reflective

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Reflector
(prismatic)
Target
T
RTransmitter
/Receiver
Optical sensors (Retro-reflective)
Type : Retro reflective

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Reflector
(prismatic)
T
RTransmitter
/Receiver
Optical sensors (Retro-reflective)
Type : Retro reflective

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Reflector
(prismatic)
T
RTransmitter
/Receiver
Optical sensors (Retro-reflective)
Type : Retro reflective

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Reflector
(prismatic)
T
RTransmitter
/Receiver
Optical sensors (Retro-reflective)
Type : Retro reflective

22. 17.10.03 No. 23 / 91© Festo Didactic – Training and Consulting Sensors
Reflector
(prismatic)
T
RTransmitter
/Receiver
Optical sensors (Retro-reflective)
Type : Retro reflective

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Reflector
(prismatic)
T
RTransmitter
/Receiver
Optical sensors (Retro-reflective)
Type : Retro reflective

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Reflector
(prismatic)
T
RTransmitter
/Receiver
Optical sensors (Retro-reflective)
Type : Retro reflective

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Reflector
(prismatic)
Sensing distance : 1/2 to 1/3 of through-beam type
Not suitable for reflective or transparent targets
Target should be larger than the reflector
T
R
Type : Retro reflective
Transmitter
/Receiver
Optical sensors (Retro-reflective)

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Type : Diffuse
Optical sensors (Diffuse)

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Target
T
RTransmitter
/Receiver
Optical sensors (Diffuse)
Type : Diffuse

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T
RTransmitter
/Receiver
Optical sensors (Diffuse)
Type : Diffuse

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T
RTransmitter
/Receiver
Optical sensors (Diffuse)
Type : Diffuse

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T
RTransmitter
/Receiver
Optical sensors (Diffuse)
Type : Diffuse

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T
RTransmitter
/Receiver
Optical sensors (Diffuse)
Type : Diffuse

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T
RTransmitter
/Receiver
Optical sensors (Diffuse)
Type : Diffuse

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Transmitter
/Receiver
Sensing distance: much less than reflex type, actual distance depends on colour and
reflective nature of the surface
Larger targets result in longer sensing distances
Not suitable for dirty environments
T
R
Optical sensors (Diffuse)
Type : Diffuse

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Inductive sensors

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Connection cable
LED indicator
Resonant circuit coil
Active surface
High frequency magnetic
field
(300 to 800 kHz)
Inductive sensors

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Sensor
Oscillation
Amplitude
Sensor
output
signal
ON
OFF
Targ
et
Inductive sensors

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ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
Inductive sensors

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ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
Inductive sensors

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ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
Inductive sensors

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ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
Inductive sensors

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ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
Inductive sensors

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ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
Inductive sensors

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ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
Inductive sensors

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ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
Inductive sensors

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Will detect any conductive material
Quoted distances are for mild steel
Sensor performance can be affected by:
• Temperature
• Target material
• Target dimensions
Inductive sensors

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Reed switch

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Glass Tube filled
with nitrogen
Reed
contacts
LED
indicator
Reed switch

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Reed switch

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Reed switch

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Reed switch

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Reed switch

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Reed switch

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Reed switch

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24v
Reed switch

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24v
Reed switch

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Interference from other magnetic fields must be avoided.
If positioned in mid stroke, switching point will vary depending on direction of approach.
Maximum current must be limited to avoid burning of the reed contacts.
Reed switch

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Inductive magnetic sensor

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Connection
cable
LED
Indicator
Resonant circuit
coil
High
frequency
magnetic
field
Inductive magnetic sensor

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Inductive magnetic sensor

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Inductive magnetic sensor

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Inductive magnetic sensor

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Inductive magnetic sensor

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Inductive magnetic sensor

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Inductive magnetic sensor

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Inductive principle of operation - but only reacts to magnetic fields
Interference from other magnetic fields must be avoided.
Solid state device - higher switching frequency - 1kHz
Inductive magnetic sensor

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Capacitive sensor

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Connection cable
Adjusting screw
LED indicator
Active surface
Active electrode
Earth electrode
Electrostatic field
Sensor is looking for a
change in capacitance in the
active field
Capacitive sensor

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Target
Capacitive sensor

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Capacitive sensor

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Capacitive sensor

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Capacitive sensor

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Detects any material denser than air (as
long as there is enough of it)
Can be adjusted for sensitivity
Can be affected by dusty environments
Capacitive sensor

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Sensor is adjusted so that
it does not ‘see’ the wall of
the vessel.
Capacitive sensor

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As the level rises the fluid
affects the sensor field.
Capacitive sensor

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Until the sensor switches.
Capacitive sensor

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Sensor symbols

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+ 18 to 30 Volts
DC.
0 V
Output
Inductive
Capacitive
Optical
Magnetic
Ultrasonic
Normally
open
Normally
closed
Sensor symbols

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+ 18 to 30 Volts
DC.
0 V
Capacitive Sensor with
Normally open function
Output
Sensor symbols

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Sensor connection

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+ 18 to 30 Volts DC
0 V
Output
24v
DC
0v
PNP Type
• Output is Positive
• Positive switching
Sensor connection

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NPN Type
• Output switches
through to 0v
• Negative switching
+ 18 to 30 Volts DC
0 V
Output
24v
DC
0v
Sensor connection

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Sensor connection

83. 17.10.03 No. 84 / 91© Festo Didactic – Training and Consulting Sensors
+ 18 to 30 Volts
DC.
0 V
Output
Inductive
Capacitive
Optical
Magnetic
Ultrasonic
Normally
open
Normally
closed
Sensor connection

84. 17.10.03 No. 85 / 91© Festo Didactic – Training and Consulting Sensors
Will detect any conductive material
Quoted distances are for mild steel
Sensor performance can be affected by:-
• Temperature
• Target material
• Target dimensions.
ON
OF
F
Targe
t
Sensor
Oscillation
Amplitude
Sensor
output
signal
Inductive sensor

85. 17.10.03 No. 86 / 91© Festo Didactic – Training and Consulting Sensors
Detects any material denser than air.
(as long as there is enough of it)
Can be adjusted for sensitivity
Can be affected by dusty environments
Capacitive sensor

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Target
Type: Through-beam
Long sensing distance : up to 30 metres
with some devices
Will detect all but very transparent
materials
Must be accurately aligned
Transmitter Receiver
Optical sensors

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Transmitter / Receiver Reflector
(prismatic)
Type: Retro-reflective
Sensing distance : 1
/2 to 1
/3 of through-
beam type.
Not suitable for reflective or transparent
targets
Target should be larger
than the reflector
T
R
Optical sensors

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Transmitter /
Receiver
Type : Diffuse
Sensing distance : much less than reflex
type, actual distance depends on colour
and reflective nature of the surface
Larger targets result in longer sensing
distances
Not suitable for dirty
environments
T
R
Optical sensors

89. 17.10.03 No. 90 / 91© Festo Didactic – Training and Consulting Sensors
Interference from other
magnetic fields must be
avoided.
If positioned in mid stroke,
switching point will vary
depending on direction of
approach.
Maximum current must be
limited to avoid burning of the
reed contacts.
Reed switch

90. 17.10.03 No. 91 / 91© Festo Didactic – Training and Consulting Sensors
Inductive principle of operation - but
only reacts to magnetic fields
Interference from other magnetic
fields must be avoided
Solid state device - higher switching
frequency - 1kHz
Inductive magnetic sensor