Banner WORLD-BEAM QS18 Laser Series - Manual (Page 2)

These adjustable-field sensors are able to detect objects of relatively low reflectivity, while ignoring other objects in the background (be-
yond the cutoff point). The cutoff distance is mechanically adjustable, using the 5-turn adjustment screw on the sensor top (see
Figure 1.
Sensor features on page 2). Backgrounds and background objects must always be placed beyond the cutoff distance.
Figure 1. Sensor features
1 Green: Power Indicator (Flashes for Output Overload)
2
Yellow: Light Sensed Indicator (Flashes for Low Gain
Conditions)
3 Cutoff Point Adjustment Screw
Adjustable-Field Sensing — Theory of Operation
The sensor compares the reflections of its emitted light beam (E) from an object
back to the sensor’s two differently-aimed detectors R1 and R2 (see
Figure 2.
Adustable field sensing concept on page 2). If the near detector (R1) light sig-
nal is stronger than the far detector (R2) light signal (see object A, closer than the
cutoff distance), the sensor responds to the object. If the far detector (R2) light
signal is stronger than the near detector (R1) light signal (see object B, object be-
yond the cutoff distance), the sensor ignores the object.
The cutoff distance for these sensors is adjustable. Objects lying beyond the cut-
off distance are ignored, even if they are highly reflective. However, it is possible
to falsely detect a background object, under certain conditions (see
Background
Reflectivity and Placement on page 3).
In the drawings and discussion on these pages, the letters E, R1, and R2 identify
how the sensor’s three optical elements (Emitter “E”, Near Detector “R1”, and Far
Detector “R2”) line up across the face of the sensor. The location of these ele-
ments defines the sensing axis (see
Figure 3. Sensing Axis on page 3). The
sensing axis becomes important in certain situations, such as those illustrated in
Figure 7. Object beyond cutoff – problem on page 4 and Figure 8. Object be-
yond cutoff – solution on page 4.
R1
Receiver
Elements
R2
Lenses
Object
A
Object B
or
Background
Sensing
Range
Cutoff
Distance
E
Near
Detector
Far
Detector
Figure 2. Adustable field sensing concept
WORLD-BEAM® QS18 Adjustable-Field Sensors
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Rev. I