Page 395 - Sensors and Systems - North American Catalog
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Photoelectric Sensors
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Photoelectric Sensors
Introduction
4. Thru-Beam Sensors
The emitter and receiver of the thru-beam sensor are in separate
housings.The emitter (E) is aimed directly into the receiver (R). If an
object (O) obstructs the light beam, the output is switched.
R
E
O
Features:
•
Detects opaque and reflective objects
•
Long range and high reliability because the light beam only
travels one path, from the emitter to the receiver
•
Not significantly affected by contamination and, therefore,
suitable for applications in harsh environments. Possible
applications include outside installations or in dirty or dusty
environments.
Typically, thru-beam sensors are used to monitor production and
packaging lines (see the following figure), to measure fill levels
in transparent containers, or as a safety measure for doors and
dangerous areas. There is, however, an additional expense
because both units need to be mounted and wired.
Receiver
Emitter
Special versions of thru-beam sensors
Photoelectric slot sensors
If the distance between the emitter and receiver is
small - a few millimeters or centimeters - the two can
be positioned across from each other in a u-shaped
housing. Since wiring is only required for one device,
slot style sensors (see the following figure) are
easier to mount and wire. In addition, there is no
need to align the emitter to the receiver.
E
S
S
E
Light grids
In safety and some nonsafety applications, the task
at hand often involves monitoring a large surface.
The easiest way to achieve this is by arranging
a number of thru-beam sensors parallel to each
other. In a light grid of this type, all emitters are
combined in a single housing. This also applies
to the receivers, any of which can switch the light grid’s output.
This reduces installation time and expense when compared to a
comparable number of thru-beam sensors. The distances between
the individual beams of the grid can be selected specifically for the
application.
Slot grid sensors
Slot grid sensors are designed for filling and counting applications.
Unlike standard slot sensors, slot grid sensors create a sheet of
light between the forks for object detection and offer maximum
response time of 100 ms with target object sizes as small as 1mm.
Slot grid sensors are available in 4 sizes and offer active sensing
fields from 34 mm x 50 mm up to 142 mm x 150 mm. Dynamic mode
sensing can be used to detect only moving targets and ignore static
objects in the sensing field.
