Rockwell Automation 2755 AtomScan Bar Code Reader - Manual (Page 25)

3–5 Designing Your Scanner System
Publication 2755-6.9
When to Use a Raster Reader
Single line readers should always used in step ladder orientation.
Raster readers are beneficial in picket fence applications with
symbols printed by a dot matrix printer, where the bars have ragged
edges or voids, or where the spaces have specks in them.
The AtomScan + reader might read a symbol correctly even if the
symbol or package is not correctly oriented. Refer to the figure
below for various package orientations. Tilt, pitch, and skew can
affect the reader’s ability to read bar code symbols.
Reader
Correctly Positioned
Symbol and Package
Tilted Symbol
Pitched Package
and Symbol
Skewed Package
and Symbol
Tilt
A symbol is tilted when the symbol’s bars are not 90
°
to the scan
line. The symbol can be read with any tilt, provided the scan line
passes through all bars and quiet zones on each sweep for the
required minimum number of scans. Tilt may reduce the number of
scans in a given application.
Pitch
A symbol is pitched when the symbol’s bars are at different distances
from the reader. From the reader’s perspective, a pitched symbol
appears to have a smaller narrow element width than it actually has.
This may reduce both the read rate and the read range. However, the
symbol can still be read if the apparent narrow element width is
within the reader’s specifications.
Note: Like skew, pitch may be used deliberately to reduce specular
reflection, as long as the application still has the number of scans per
symbol it needs.
Tilt, Pitch, and Skew