Cut Sheet

Sensing Reliability
For highest sensivity, 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 show excess gain versus sensing distance for 200 mm and 1 m cutos. Maximum excess gain for a
200 mm cuto occurs at a lens-to-object distance of about 150 mm, and for a 1 m cuto, at about 400 mm. The background must be
placed beyond the cuto distance. Following these two guidelines makes it possible to detect objects of low reecvity, even against
close-in reecve backgrounds.
Background Reecvity and Placement
Avoid mirror-like backgrounds that produce specular reecons. A false sensor response occurs if a background surface reects the
sensor's light more to the near detector (R1) than to the far detector (R2). The result is a false ON condion (Figure 5 on page
4).
Correct this problem by using a diusely reecve (mae) background, or angling either the sensor or the background (in any plane) so
the background does not reect light back to the sensor (Figure 6 on page 4). Posion the background as far beyond the cuto
distance as possible.
An object beyond the cuto distance, either staonary (and when posioned as shown in Figure 7 on page 4), or moving past the
face of the sensor in a direcon perpendicular to the sensing axis, may cause unwanted triggering of the sensor if more light is reected
to the near detector than to the far detector. Correct the problem by rotang the sensor 90° (Figure 8 on page 4). The object then
reects the R1 and R2 elds equally, resulng in no false triggering. A beer soluon, if possible, may be to reposion the object or the
sensor.
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 5. Reecve Background - Problem
E
R2
R1
E = Emitter
R1
= Near Detector
R2 = Far Detector
Cutoff
Distance
Reflective
Background
Strong
Direct
Reflection
A
way From
Sensor
Sensing
Field
Core of
Emitted
Beam
Figure 6. Reecve Background - Soluon
Sensing
Field
Cutoff
Distance
E
R2
R1
A reecve background object in this posion or moving across the sensor face
in this axis and direcon may cause a false sensor response.
Figure 7. Object Beyond Cuto - Problem
Sensing
Field
ON
OFF
DELAY DELAY
DO
SIG
LO
RANGE
E, R1, R2
A reecve background object in this posion or moving across the sensor face
in this axis is ignored.
Figure 8. Object Beyond Cuto -
Soluon
Color Sensivity
The
eects of object reecvity on cuto distance, though small, may be important for some applicaons. It is expected that at any
given cuto seng, the actual cuto distance for lower reectance targets is slightly shorter than for higher reectance targets. This
behavior is known as color sensivity.
These excess gain curves were generated using a white test card of 90% reectance. Objects with reecvity of less than 90% reect
less light back to the sensor, and thus require proporonately more excess gain in order to be sensed with the same reliability as more
reecve objects. When sensing an object of very low reecvity, it may be especially important to sense it at or near the distance of
maximum excess gain.
Q60AFV Series Sensors with Visible Red Emier
4 www.bannerengineering.com - Tel: [phone] P/N 69622 Rev. C