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CS2 Color Scanner
Application Guidelines
Power Supplies
The silicon cell used in the CS2 is electrically connected to
its metal package which is connected to the CS2's metal
enclosure. Therefore the CS2 must be connected to a good
ground, preferably the same ground as the machinery around
it, and the signals from the CS2 isolated. The CS2 must be
powered by a dedicated power supply, and the optional
analog inputs and outputs must be isolated if they are used.
The Limit outputs are isolated in the CS2.
Electrical noise
The signal level from the silicon cell is low and is amplified
by high speed circuitry. This circuitry is sensitive to
electrical noise from intense electrical fields. The CS2's
metal enclosure is an adequate shield against most electrical
interference. Use high quality shielded cable to reduce
electrical noise. If analog inputs or outputs are used, they
should be wired using individually shielded, twisted pairs.
Data Skew
The CS2 reads colors one at a time, in sequence. The Base
color is captured 22 microseconds after the Sense color. If
an object is moving while it is scanned, the information from
the two colors will be skewed slightly. If an abrupt change
in data occurs, the Sense/Base ratio will be momentarily
incorrect. Usually this will not cause any problems. If it is a
problem, it can be filtered out, either electronically in stand-
alone applications or with a software filter when used with a
computer. The data skew can also be reduced by decreasing
the LED time (contact Delta for more information).
Color Errors
The CS2 uses an unfiltered silicon cell which captures all
reflected light. It determines color by turning on only the
desired color at a given time. The wavelength of the LED
lighting is a function of the LEDs. This wavelength varies
slightly with temperature.
Ambient light, or any other extraneous light, is an error
source. The CS2's LEDs are very bright, so reasonable
amounts of ambient light can be tolerated. (Don't be fooled
by the apearance of the CS lighting. The LEDs are only on
about 5% of the time. Your eyes average this light, making
it appear 20 times less intense.)
Background Errors
In order to see objects, it is necessary to distinguish them
from the background. To maintain a good contrast, the
background should be black in the color spectrum of
Delta Computer Systems, Inc., 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688
email@deltacompsys.com http://www.deltacompsys.com
interest. If the background is paintable, a flat black paint
such as Krylon 1602 can be used. Most black belting is also
acceptable. Wet or otherwise reflective surfaces actually
produce low background readings as long as light cannot
reflect directly back into the viewer.
Because the light from the CS2 tends to dissipate in all
directions, increasing the distance from the CS2 to the
background will reduce the background readings. If this is
done, be sure the increased distance does not allow ambient
light to become a problem.
Usable results can sometimes be obtained even if the
background cannot be made totally black. However, the
object signal should be at least twice as strong as the
background signal. The background will also contribute
more errors if the Sense/Base ratio of the background is very
different from the Sense/Base ratio of the objects. If this is
the case the background signal must be reduced to an
insignificant level.
Reflections
When either the CS2 lighting or ambient light is allowed to
reflect directly into the scanner it will overdrive the circuitry
and cause meaningless outputs. Usually this condition can
be avoided by controlling the relative angle of the scanner to
the objects and background.
In some applications it is impossible to avoid an occasional
reflection. In these cases, an external optimizing computer
can be used to "trap" the overdrive readings and ignore
them. This technique avoids making decisions on bad data,
but the overdriven data are still lost.
Intensity Variations
The CS2 lighting pattern is made up of multiple LEDs; some
variation in intensity is to be expected. The larger the
viewing area, (length, width, and depth), the more intensity
variation will occur. The LEDs used in the CS2 are
specially selected and the light pattern is optimized at the
factory. The default configuration pattern is optimized for
low ratio limit operation. The light pattern is adjusted such
that objects outside the specified viewing area but still
within the lighting area will not be read as having low
Sense/Base ratios, thus eliminating false limits. If needed,
other light pattern optimization techniques can be used.
Using Multiple CS2s
The scanning area of the CS2 is limited to about 1.25" by
the lighting. However, multiple CS2s can be used to cover a
wide area. Care must be taken to avoid interference between
the units.
This is easily accomplished by either physical
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