348
Photoelectric Sensors
2
Photoelectric Sensors,
Standard Sensors,
thru-beam sensors
2
.1.4
Photoelectric Sensors,
Standard Sensors,
thru-beam sensors
2
.1.4
Photoelectric Sensors,
Standard Sensors,
retroreflective sensors
2
.1.3
Photoelectric Sensors,
Standard Sensors,
retroreflective sensors
2
.1.3
Photoelectric Sensors,
Standard Sensors,
diffuse mode sensors
2
.1.2
Photoelectric Sensors,
Standard Sensors,
diffuse mode sensors
2
.1.2
Photoelectric Sensors,
Standard Sensors,
diffuse mode sensors with background suppression
2
.1.1
Photoelectric Sensors,
Standard Sensors,
diffuse mode sensors with background suppression
2
.1.1
Photoelectric Sensors,
Standard Sensors,
distance sensors
2
.1.5
Photoelectric Sensors,
Standard Sensors,
fiber optic sensors
2
.1.6
Germany: +49 621 776-4411
Consider the General Notes on the Information in the Pepperl+Fuchs Product Catalogs
Pepperl+Fuchs Group
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USA: +1 330 486 0001
fa-info@us.pepperl-fuchs.com
Singapore: +65 6779 9091
fa-info@sg.pepperl-fuchs.com
Copyright Pepperl+Fuchs
The Functional Principles at a Glance
The photoelectric sensors or photo sensors used in automation
provide all the benefits of rapid and noncontact detection. Our
wide range of photoelectric standard sensors is suitable for all
noncontact object detection solutions. The many different ver-
sions available mean that it is always possible to find the best
possible sensor for any application. Ongoing development of
these sensors is setting new market trends through innovations
such as the measuring photoelectric sensor or the efficient con-
nection of sensors to the control hierarchy via IO-Link.
AT A GLANCE
•
Various functional principles are available:
•
Thru-beam sensors
•
Retroreflective sensors
•
Energetic diffuse mode sensors or background suppression
sensors
•
Fiber optic sensors with compatible fiber optic cables
•
Contrast sensors and color sensors
•
Photoelectric slot and slot grid sensors
•
Light grids
•
Brass, stainless steel, or plastic housing
•
From miniature housings to cylindrical threaded housing to
robust compact sensors
•
Innovative functions for easy setup and safe operation
1.
Background suppression sensors
Background suppression sensors were developed
to reach a defined detection range for any object,
regardless of its brightness, color, or other charac-
teristics such as the brightness of the background.
The following figure illustrates the functional prin-
ciple of a background suppression sensor. The
light emitted by the emitter is directed by the lens and hits the
object. If the object is located within the detection range, a por-
tion of the reflected light, bundled by the receiver lens, is mapped
to the near element of the receiver (N); the sensor outputs the
“
switched on” signal.
As the object’s distance increases, this light spot moves in the
direction of the far element (F). At the detection range limit, one
half of the light spot is on the near element, the other on the far
element and the sensor registers “off.” If the object moves further
away, the light only hits the far element and the sensor still reg-
isters “off.”
Emitter
Object in
sampling range
Detection range
Background
Bright
background
Object in the
background
Scanning range
Near element
receives more light –
object is detected
Far element
receives more light –
object is ignored
Scanning range
Receiver
Far
Near
Emitter
Receiver
Far
Near
Features:
•
Almost constant detection range for diffuse reflecting
materials with extremely different degrees of remission.
•
Dark objects in front of a light background are reliably
detected.
•
Insensitive to interfering reflections from objects outside of the
specified detection range.
•
High excess gain.
•
Minimal mounting effort as the sensor consists of one unit and
does not require a reflector.
Similarly to background suppression, it is also possible to make
use of foreground suppression. These sensors ignore all objects
that are located closer to the sensor than the preset minimum
detection range.
Measuring photoelectric sensors
Measuring photoelectric sensors combine the ad-
vantages of background/foreground suppression
with the measuring functionality of a distance sen-
sor. An integrated measuring core, otherwise
found only in distance sensors, enables different
switching functions in one device and provides
outstanding performance data.
Convergent mode sensors
Convergent mode sensors function similarly to
background suppression sensors, although the
distance between the object and the background
is greater. Due to this compromise in terms of se-
lectivity, this device is offered at an extremely at-
tractive cost/benefit ratio. These sensors are the
first choice where suppression of an existing background is re-
quired in the application despite high cost pressures.
Background evaluation sensors
In addition to background suppression, the re-
verse principle–background evaluation–is also
used in certain applications.While the one method
ignores the background and detects only objects
within the detection range, the other evaluates
only the light reflected from the background: the
background becomes the reference rather than the object (see
Fig.). If an object interrupts the light path to the background, the
sensor switches, regardless of whether or not the reflected light
reaches the receiver again and indicates a detected object be-
fore the background–such as with reflective objects.
Background evaluation sensors do not have a blind zone and are
especially suitable for detecting complex, highly reflective ob-
jects. In contrast to systems with background suppression, they
can also be tested and support self-monitoring.
Receiver
Vehicle is only
detected in
background
evaluation mode
Receiver
Receiver
Back-
ground
is
detected
Vehicle is
detected
I
Near
< I
Far
= OFF
I
Near
> I
Far
= ON I
Near
= I
Far
= 0 = ON
Emitter
Emitter
Near Far
Near Far
Emitter
Near Far
Photoelectric Sensors
