Banner M18 Series - Manual (Page 4)

In the drawings and discussion, 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. In figures Reflective Background - Problem, Reflective Background - Solution, and
Object Beyond Cutoff - Problem, these elements align vertically; in Object Beyond Cutoff - Solution, they align horizontally. Note how the
position of the tabs on the front of the sensor helps to define the sensing axis of the sensor (Sensing Axis). The sensing axis becomes
important in situations like those illustrated in the Object Beyond Cutoff figures.
Sensing
Axis
R2
R1
E E
R2
R1
E = Emitter
R1 = Near Detector
R2 = Far Detector
M18FF Sensor
Core of
Emitted
Beam
Cutoff
Distance
Reflective
Background
Strong
Direct
Reflection
to R1
Fixed Sensing
Field
E
R2
R1
E = Emitter
R1 = Near Detector
R2 = Far Detector
M18FF Sensor
Core of
Emitted
Beam
Cutoff
Distance
Reflective
Background
Strong
Direct
Reflection
Away From
Sensor
Fixed Sensing
Field
Sensing Axis. Reflective Background - Problem Reflective Background - Solution
As a general rule, the most reliable sensing of an object approaching from the side occurs when the line of approach is parallel to the
sensing axis.
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 strongly to the near detector (R1) than to the far detector (R2). The result is
a false ON condition (Reflective Background - Problem). Use of a diffusely-reflective (matte) background will cure this problem. Other
possible solutions are to either angle the sensor or angle the background (in any plane) so that the background does not reflect back to
the sensor (Reflective Background - Solution).
An object beyond the cutoff distance, either moving or stationary (and when positioned as shown in Object Beyond Cutoff - Problem), can
cause unwanted triggering of the sensor because it reflects more light to the near detector than to the far detector. Remedy the problem
easily by rotating the sensor 90° (Object Beyond Cutoff - Solution) to align the sensing axis horizontally. 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.
Unwanted triggering of the sensor from an object beyond the cutoff can also be caused by attempting to sense a small object moving
perpendicular to the sensor face, or by an object moving through the off-center position shown. Making the object larger, centering the
sensor relative to the object, or rotating the sensor to place the sensing axis perpendicular to the longer dimension of the object (Object
Beyond Cutoff - Solution) will solve the problem.
E
R2
R1
E = Emitter
R1 = Near Detector
R2 = Far Detector
Area of R1 Response
Area of R2 Response
Area of R1 and R2 Response
Reflective
Background or
Moving Object
M18FF Sensor
Cutoff
Distance
Fixed Sensing
Field
R1 Response
R2 Response
E, R2, R1
E = Emitter
R1 = Near Detector
R2 = Far Detector
Area of R1 and R2 Response
M18FF Sensor
Reflective
Background
or Moving
Object
Cutoff
Distance
Fixed Sensing
Field
Object Beyond Cutoff - Problem Object Beyond Cutoff - Solution
EZ-BEAM M18 Series Sensors
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