Banner Q60 Background Suppression Series - Manual (Page 3)

page 3
Q60V Series Adjustable-Field Sensors –
Visible Red Emitter
Banner Engineering Corp. • Minneapolis, MN U.S.A.
www.bannerengineering.com • Tel: 763.544.3164
Sensor Setup
Setting the Cutoff Distance
The cutoff distance for Q60AFV sensors may be adjusted between 200 mm and
1000 mm (8" to 40").
To maximize contrast, position the lightest possible background to be used, at the
closest position it will come to the sensor during use (Figure 4). Using a small
screwdriver in the adjustment screw, adjust the cutoff distance until the threshold is
reached and the green Light Sensed indicator changes state. (If the indicator never
comes ON, the background is beyond the maximum sensing cutoff and will be
ignored.) Note the position of the rotating cutoff position indicator at this position.
Then repeat the procedure, using the darkest target, placed in its most distant
position for sensing. Adjust the cutoff so that the indicator is midway between the two
positions (Figure 5).
NOTE: Setting the cutoff distance adjustment screw to its maximum clockwise
position places the receiver lens directly in front of the receiver elements and
results in the Q60 performing as a long-range diffuse sensor.
Sensing Reliability
For highest sensitivity, the sensor-to-object distance should be such that the object
will be sensed at or near the point of maximum excess gain. The excess gain curves
on page 1 show excess gain vs. sensing distance for 200 mm and 1 m cutoffs.
Maximum excess gain for a 200 mm cutoff occurs at a lens-to-object distance of
about 150 mm, and for a 1 m cutoff, at about 400 mm. The background must be
placed beyond the cutoff distance. Following these two guidelines makes it possible
to detect objects of low reflectivity, even against close-in reflective backgrounds.
Background Reflectivity and Placement
Avoid mirror-like backgrounds that produce specular reflections. False sensor re-
sponse will occur if a background surface reflects the sensor’s light more strongly to
the near detector (R1) than to the far detector (R2). The result is a false ON condition
(Figure 6). Use of a diffusely-reflective (matte) background will cure this problem.
Other possible solutions are to angle either the sensor or the background (in any
plane) so that the background does not reflect back to the sensor (see Figure 7).
An object beyond the cutoff distance, either moving or stationary (and when posi-
tioned as shown in Figure 8), can cause unwanted triggering of the sensor because it
reflects more light to the near detector than to the far detector. The problem is easily
remedied by rotating the sensor 90° (Figure 9) to align the sensing axis horizontally.
The object then reflects the R1 and R2 fields equally, resulting in no false triggering.
Figure 6. Reflective background – problem
Cutoff
Distance
Reflective
Background
Sensing
Field
E
R2
R1
E = Emitter
R1 = Near Detector
R2 = Far Detector
Core of
Emitted
Beam
Strong
Direct
Reflection
to R1
Figure 7. Reflective background – solution
E
R2
R1
E = Emitter
R1 = Near Detector
R2 = Far Detector
Cutoff
Distance
Reflective
Background
Strong
Direct
Reflection
Away From
Sensor
Sensing
Field
Core of
Emitted
Beam
Target Background
Cutoff
Distance
E
R2
R1
Figure 4. Set cutoff distance approximately
midway between the farthest
target and the closest background
ON
DELAY
DO
RANGE
In
cr
e
a
si
ng
Di
st
an
ce
Set Cutoff Midway
Between
Farthest Target Object
Closest Background
Figure 5. Setting the cutoff distance
Figure 8. Object beyond cutoff distance —
problem
Sensing
Field
Cutoff
Distance
E
R2
R1
Figure 9. Object beyond cutoff distance —
solution
Sensing
Field
ON OFF DELA
Y
DELA
Y
DO SIG LO
RANGE E, R1, R2