Figure 5. object beyond cutoff - problem, Figure 6. object beyond cutoff - solution, Figure 3. reflective back – Banner T30 Series User Manual
Page 3: Ground - problem, Figure 4. reflective background - solution, Color sensitivity, Figure 3. reflective background - problem
E = Emitter
R1 = Near Detector
R2 = Far Detector
R2
R1
E
Fixed
Sensing
Field
Strong
Direct
Reflection
to R1
Core of
Emitted
Beam
Cutoff
Distance
Reflective
Background
T30FF
Figure 3. Reflective Background - Problem
E = Emitter
R1 = Near Detector
R2 = Far Detector
R2
R1
E
Fixed Sensing Field
Strong Direct
Reflection
Away
From Sensor
Core of
Emitted
Beam
Cutoff
Distance
Reflective
Background
T30FF
Figure 4. Reflective Background - Solution
Fixed
Sensing
Field
Cutoff
Distance
R1 = Near Detector
R2 = Far Detector
E = Emitter
T30FF
R1
E
R2
Reflective
Background
or
Moving Object
A reflective background object in this position or moving across
the sensor face in this axis and direction may cause false sensor
response.
Figure 5. Object Beyond Cutoff - Problem
E = Emitter
R2 = Far Detector
R1 = Near Detector
T30FF
E, R2, R1
Fixed
Sensing
Field
Cutoff
Distance
Reflective
Background
or
Moving Object
A reflective background object in this position or moving across
the sensor face in this axis will be ignored.
Figure 6. Object Beyond Cutoff - Solution
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 is slightly shorter than for higher reflectance targets. This behavior is
known as color sensitivity.
For example, an excess gain of 1 (see
on 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. An object of this reflectivity results in a far limit cutoff of approximate-
ly 190 mm (7.5 in) for the 200 mm (8 in) cutoff model, for example; thus 190 mm represents the cutoff for this sensor and target.
These excess gain curves 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.
T30 Sensors - DC-Voltage Series
P/N 121524 Rev. A
www.bannerengineering.com - tel: 763-544-3164
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