Banner WORLD-BEAM QS30 Series - Manual (Page 3)

P/N 119166 rev. B
3
Banner Engineering Corp. • Minneapolis, MN U.S.A.
www.bannerengineering.com • Tel: 763.544.3164
WORLD-BEAM
®
QS30 – Universal Voltage
Color Sensitivity
The effects of object reflectivity on cutoff distance, though small, may be important for
some applications. It is expected that at any given cutoff setting, the actual cutoff distance
for lower reflectance targets will be slightly shorter than for higher reflectance targets.
This behavior is known as color sensitivity.
For example, an excess gain of 1 (see page 5) for an object that reflects 1/10 as much
light as the 90% white card is represented by the horizontal graph line at excess gain
= 10. This line intersects the curve at approximately 190 mm. Thus, an object of this
reflectivity results in a far limit cutoff of approximately 190 mm (7.5") for the 200 mm
cutoff model, for example; and 190 mm represents the cutoff for this sensor and target.
The excess gain curves on page 5 were generated using a white test card of 90%
reflectance. Objects with reflectivity of less than 90% reflect less light back to the sensor,
and thus require proportionately more excess gain in order to be sensed with the same
reliability as more reflective objects. When sensing an object of very low reflectivity, it
may be especially important to sense it at or near the distance of maximum excess gain.
QS30FF
R1 = Near Detector
R2 = Far Detector
E = Emitter
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Cutoff
Distance
Reflective
Background
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R1
R2
E
Fixed
Sensing
Field
Cutoff
Distance
R1 = Near Detector
R2 = Far Detector
E = Emitter
QS30FF
R1
R2
E
Reflective
Background
or
Moving Object
Figure 3. Reflective background – problem Figure 4. Reflective background – solution
Figure 5. Object beyond cutoff – problem Figure 6. Object beyond cutoff – solution
Fixed
Sensing
Field
E = Emitter
R2 = Far Detector
R1 = Near Detector
QS30FF
Cutoff
Distance
E, R2, R1
Reflective
Background
or
Moving Object
QS30FF
R1
R2
E
R1 = Near Detector
R2 = Far Detector
E = Emitter
Core of
Emitted
Beam
Reflective
Background
Fixed Sensing
Field
Strong
Direct
Reflection
Away
From Sensor
Cutoff
Distance
A reflective background object in this position or
moving across the sensor face in this axis and
direction may cause false sensor response.
A reflective background object in this position or
moving across the sensor face in this axis will be
ignored.