Rockwell Automation 2755 AtomScan Bar Code Reader - Manual (Page 24)

3–4 Designing Your Scanner System
Publication 2755-6.9
Picket Fence
In picket fence orientation, the symbol can be read the whole time it
is in the read range, rather than being limited by the height of the bar
code. However, picket fence allows scanning of only a small part of
the whole symbol. Slight imperfections such as extraneous ink or
voids can cause misreads or non-reads. The quality of data in picket
fence orientation can be improved by any of the following.
•
Make sure the printing on the symbol is of good quality.
•
Tilt the scan line slightly to allow a larger part of the symbol to be
scanned as it passes through the scan line.
Direction
of Travel
Direction
of Travel
Reader
Reader
Step Ladder
In general, step ladder orientation is preferred over picket fence
orientation because each scan covers a slightly different part of the
symbol. This means that:
•
imperfections in the symbol are less liable to prevent a successful
read, and
•
symbol placement is not as critical.
Direction of
Travel
Direction of
Travel
Reader
Reader