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

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

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

Reflective

Background

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

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

Performance Curves

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