Banner T30 Series - Manual (Page 2)

The cutoff distance for model T30 Series sensors is fixed at 200, 400 or 600 millimeters (7.9 in, 16.7 in, or 23.6 in). Objects lying beyond
the cutoff distance are usually ignored, even if they are highly reflective. However, under certain conditions, it is possible to falsely detect
a background object (see
Background Reflectivity and Placement on 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 discussion 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 illustra-
ted 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. See Performance Curves on
page 5 for the excess gain curves for these sensors. 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. Follow-
ing these two 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 Back-
ground - Problem on page 3). 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 3). 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, can 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.
T30 Sensors - AC-Voltage Series
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