M186E Datasheet, PDF (4/8 Pages) List of Unclassifed Manufacturers – Stainless Steel 18 mm Barrel-style DC Photoelectric Sensors

EZ-BEAM M18 Series Sensors
EZ-BEAM M18 Series Fixed-Field Sensor Setup Tips
General
For highest sensitivity, the sensor-to-object distance should be such that the object
will be sensed at or near the point of maximum excess gain (see page 3). The
background must be placed beyond the cutoff distance. Following these two
guidelines makes it possible to detect objects of low reflectivity, even against close-in
reflective backgrounds.
In the drawings and discussion on this page, 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. In Figures 2, 3, and 4, these elements
align vertically; in Figure 5, 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 (Figure 1,
right). The sensing axis becomes important in situations like those illustrated in
Figures 4 and 5 below.
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 (Figure 2). 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
(see Figure 3).
An object beyond the cutoff distance, either moving or stationary (and when posi-
tioned as shown in Figure 4), 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° (Figure 5) 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.
E
R2
Sensing
R1
Axis
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.
Figure 1. Sensing axis
Fixed Sensing
Field
Cutoff
Distance
M18FF Sensor
Core of
E
Emitted
Beam
R2
R1
E = Emitter
Strong
Direct
Reflection
to R1
R1 = Near Detector
R2 = Far Detector
Reflective
Background
Figure 2. Reflective background – problem
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 in Figure 4. 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 (Figure 5) will
solve the problem.
Fixed Sensing
Field
M18FF Sensor
E
R2
R1
Cutoff
Distance
Reflective
Background or
Moving Object
M18FF Sensor
Fixed Sensing
Field
Cutoff
Distance
Reflective
Background
or Moving
Object
E, R2, R1
Fixed Sensing
Field
M18FF Sensor
E
R2
R1
Core of
Emitted
Beam
E = Emitter
R1 = Near Detector
R2 = Far Detector
Cutoff
Distance
Reflective
Background
Strong
Direct
Reflection
Away From
Sensor
Figure 3. Reflective background – solution
R2 Response
E = Emitter
R1 Response
R1 = Near Detector
R2 = Far Detector
Area of R1 Response
Area of R2 Response
Area of R1 and R2 Response
E = Emitter
R1 = Near Detector
R2 = Far Detector
Area of R1 and R2 Response
Figure 4. Object beyond cutoff – problem
page 4
Figure 5. Object beyond cutoff – solution
Banner Engineering Corp. • Minneapolis, U.S.A.
Website: http://www.baneng.com • Tel: [phone]