Banner T30 Series - Manual (Page 2)

R1
R2
Lenses
Object
A
Object B
or
Background
Sensing
Range
Cutoff
Distance
E
Receiver
Elements
Near
Detector
Far
Detector
Emitter
Object is sensed if amount of light at R1
is greater than the amount of light at R2
Figure 1. Fixed-Field Concept
Sensing
Axis
R2
R1
E
Figure 2. Fixed-Field Sensing Axis
In the drawings and information provided in this document, the letters E, R1, and R2 identify how the sensor’s three optical elements (Emitter “E”, Near Detector “R1”, and
Far Detector “R2”) line up across the face of the sensor. The location of these elements defines the sensing axis, see
Figure 2. Fixed-Field Sensing Axis on page 2. The
sensing axis becomes important in certain situations, such as those illustrated in Figure 5. Object Beyond Cutoff - Problem on page 3 and Figure 6. Object Beyond
Cutoff - Solution on page 3.
Sensor Setup
Sensing Reliability
For highest sensitivity, position the target object for sensing at or near the point of maximum excess gain. Maximum excess gain for all models occurs at a lens-to-object
distance of about 40 mm (1.5 in). Sensing at or near this distance makes the maximum use of each sensor’s available sensing power. The background must be placed
beyond the cutoff distance. Note that the reflectivity of the background surface also may affect the cutoff distance. Following these guidelines will improve sensing reliability.
Background Reflectivity and Placement
Avoid mirror-like backgrounds that produce specular reflections. False sensor response will occur if a background surface reflects the sensor’s light more to the near
detector (R1) than to the far detector (R2). The result is a false ON condition (
Figure 3. Reflective Background - Problem on page 2). To cure this problem, use a
diffusely reflective (matte) background, or angle either the sensor or the background (in any plane) so the background does not reflect light back to the sensor ( Figure 4.
Reflective Background - Solution on page 2). Position the background as far beyond the cutoff distance as possible.
An object beyond the cutoff distance, either stationary (and when positioned as shown in Figure 5. Object Beyond Cutoff - Problem on page 3), or moving past the face
of the sensor in a direction perpendicular to the sensing axis, may cause unwanted triggering of the sensor if more light is reflected to the near detector than to the far
detector. The problem is easily remedied by rotating the sensor 90° (
Figure 6. Object Beyond Cutoff - Solution on page 3). The object then reflects the R1 and R2 fields
equally, resulting in no false triggering. A better solution, if possible, may be to reposition the object or the sensor.
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
T30 Series NAMUR Fixed-Field Sensors
2 www.bannerengineering.com - tel: 763-544-3164 P/N 041685 Rev. B