Scanning Considerations - Symbol PDT 7500 Series Product Reference Manual

PDT 7500 Series Product Reference Guide for DOS
5. Press the scan button.
6. If the decode is successful, the LED turns from yellow to green. The terminal may
also beep.
Note: The procedure for your scanner may differ from the one listed above.
Scanner operation depends on the application.

Scanning Considerations

Usually, scanning is a simple matter of aim, scan, and decode, and a few quick trial efforts
master it. However, two important considerations can optimize any scanning technique —
range and angle.
Range
Any scanning device decodes well over a particular working range — minimum and
maximum distances from the bar code. This range varies according to bar code density and
scanning device optics.
Scanning within range brings quick and constant decodes; scanning too close or too far away
prevents decodes. So you need to find the right working range for the bar codes you are
scanning. However, the situation is complicated by the availability of multiple integrated
scanning modules, some with specialized capabilities such as long range and 2-D decode
capability. The best way to specify appropriate working range per bar code density is through
a chart called a decode zone for each scan module. A decode zone simply plots working range
as a function of minimum element widths of bar code symbols.
Decode zones for integrated scan elements available on the PDT 7500 are provided in
Appendix A, Specifications.
Angle
Scanning angle is important for promoting quick decodes. When laser beams reflect directly
back into the scanner from the bar code, this specular reflection can "blind" the scanner.
To avoid this, scan the bar code so that the beam does not bounce directly back. But don't
scan at too sharp an angle; the scanner needs to collect scattered reflections from the scan to
make a successful decode. Practice quickly shows what tolerances to work within.
4-6