Banner R55E Series - Manual (Page 5)

page 5
R55 Color Mark Sensor
Sensitivity Adjustment
The 10-element moving LED light bar displays received light signal
strength, relative to the switch point setting. This display makes
sensitivity adjustment extremely easy and accurate.
Every color registration mark application involves sensing the
difference between two colors, which relates, optically, to
differentiating between two gray scale levels (one color returns
more reflected light to the sensor than the other). The condition
which returns the greater amount of light is referred to as the “light
condition.” The light condition is usually obvious to the eye.
However, the light bar displays exactly how the sensor “sees” the
difference between the color mark and its background.
The “Switch Point” is electronically maintained between segments
5 and 6 of the 10-element moving LED light bar display (Figure 5a).
The digital outputs switch whenever there is a transition across the
“Switch Point” (in either direction).
After mounting the R55 (see page 4), apply power to the sensor.
Hookup information is shown on a side label of the R55, and on
page 7. Alternately present the light and the dark conditions to the
R55, and adjust its Sensitivity so that the “Switch Point” is
centered between the light bar readings for the two sensing
conditions (Figure 5).
NOTE: The Sensitivity adjustment is a 15-turn potentiometer which
is clutched at both ends to prevent damage. It “free-wheels” at
both the top and the bottom end of its adjustment range.
(Clockwise rotation increases sensitivity.)
BEST SETTING IS EQUAL LEDS LIT ABOVE & BELOW SWITCH POINT
RECEIVED LIGHT
POINT SWITCH
BEST SETTING IS EQUAL LEDS LIT ABOVE & BELOW SWITCH POINT
RECEIVED LIGHT
POINT SWITCH
Light Condition
LED Segment #1 LED Segment #10
Dark Condition
Figure 5. Sensitivity Adjustment; Light and Dark
Condition Settings Should be Equally Spaced
from the Switch Point
BEST SETTING IS EQUAL LEDS LIT ABOVE & BELOW SWITCH POINT
RECEIVED LIGHT
POINT SWITCH
BEST SETTING IS EQUAL LEDS LIT ABOVE & BELOW SWITCH POINT
RECEIVED LIGHT
POINT SWITCH
Light Condition Dark Condition
Figure 5b. Minimum Recommended Contrast
BEST SETTING IS EQUAL LEDS LIT ABOVE & BELOW SWITCH POINT
RECEIVED LIGHT
POINT SWITCH
BEST SETTING IS EQUAL LEDS LIT ABOVE & BELOW SWITCH POINT
RECEIVED LIGHT
POINT SWITCH
Light Condition Dark Condition
Figure 5c. Low Contrast – All Sensing Variables Must
Remain Stable
Figure 5a. High Contrast (Best)
Sensing Contrast
In any photoelectric application, the difference in received light level between the light and dark conditions is called the optical
contrast. In general, the greater the contrast, the more reliable the sensing application will be and the more forgiving the sensor
will be to sensing variables such as vibration of the material being sensed.
Contrast is indicated on the light bar by the distance between the light condition and the dark condition; they should be equally
spaced on either side of the Switch Point. The best possible contrast is displayed when the light condition displays at segment 10
(far right) and the dark condition displays at segment 1 (far left). The minimum recommended sensing contrast for most
applications will display two segments above and below the Switch Point. Sensing for a contrast which registers at segments 5
and 6 should be reserved for applications which are perfectly stable (where no sensing variables such as vibration, color
variations, surface variations, etc. are allowed). See Figure 5.