Rockwell Automation 5000 On-Off Background Suppression Control Type 42MBS - Manual (Page 3)

ALIGNMENT
1. Set “Light Energized” (LT)/“Dark Energized” (DK) switch to de-
sired operating mode. It may be necessary to increase (counter-
clockwise) the range “coarse” adjustment to obtain access to the
LT/DK switch.
2. Loosen the lockscrew and adjust “coarse” sensing range adjust-
ment to the minimum position (full clockwise position).
3. Increase (counter clockwise) the “coarse” adjustment until the
control senses the background. In the “light” energized (LT)
mode, the red LED will turn On. In the “dark” energized (DK)
mode, the red LED will turn Off. In both cases the green LED mar-
gin indicator will turn On if the operating margin is at least 2X.
4. Using the “fine” adjustment, decrease (counter clockwise) the
sensing range until the control stops sensing the background. In
the LT mode the red LED will turn Off. In the DK mode the red
LED will turn On.
5. Place the object to be detected in front of the control at the expected
sensing distance. Both red and green LED’s should turn On in the
LT mode. The green LED should turn On and the red LED should
turn Off in the DK mode. The output should operate. The green
LED indicates that an operating margin of 2X or greater exists.
6. If the green LED does not turn On, increase the sensing range un-
til it does. Recheck to see if the control is sensing the background
by removing the object to be sensed from in front of the control. If
the background is sensed, it may not be a practical application for
the background suppression control.
7. Tighten the lockscrew after adjusting the sensing range. A slight
increase in sensing distance may occur. Typically .25 (.63cm) at
12 (30.5cm), .12 (30.5cm) at a 6 (15.2cm) and .062  (.157cm)
at 3  (7.62cm), for both background and target. If necessary sens-
ing range variation can be compensated for by adjusting to 11.75 
(29.8cm) for a 12  (30.5cm) suppression point, 5.875  (14.9cm)
for a 6  (15.2cm) suppression point, and 2.95  (7.46cm) for a 3 
(7.62cm) suppression point. Repeat steps 5 and 6 to verify the
range after the lockscrew is tightened.
APPLICATION PRECAUTIONS
To obtain the high sensitivity and sharp cut-off required in a back-
ground suppression control, two photodetectors are used. One detec-
tor senses objects in close, the other detector will sense further out.
If the further out signal (background) is greater than or equal to
the close in signal, the control remains Off, if the close signal is great-
er than the background signal, the control output will turn On.
This interdependence of the two photodetectors and overlapping
sensing areas require that the object being sensed passes by the sensor
in certain directions or false operation could occur. Therefore, an ob-
ject always should travel on an x-axis perpendicular with the control.
See figures below.
FIELD OF VIEW
OVERLAP
SUPPRESSION
POINT
FAR SENSING
AREA
OBJECT
TO BE
SUPPRESSED
Direction
of travel Control
Top View
Suppression
Point
Both
sensing ranges
overlap
OBJECT
TO BE
SUPPRESSED
CLOSE SENSING
AREA
Direction
of travel
WRONG DIRECTION OF TRAVEL CORRECT DIRECTION OF TRAVEL