RJS Inspector D4000 Auto Optic (FIRMWARE version A.05 and Earlier) - Manual (Page 64)

Operator
’
s Guide Appendix J
002-5564 RJS, Minneapolis, MN 57
Ideally, the edge contrast should be equal to symbol contrast, but as an aperture size
approaches an element size the amplitude of the signal received will decrease and the edge
contrast will decrease.
The greater the difference between minimum edge contrast and symbol contrast, the lower
the grade.
(Aperture size has the greatest affect on this parameter. The substrate material can also have
a major affect on this parameter.)
Defects
This parameter can also be “A,” “B,” “C,” “D,” or “F.”
Defects are irregularities in bars, spaces and quiet zones.
For example, a dark spot in a space could cause a low enough reflectance to be mistaken for a
bar, and the extra bar would cause a decode error.
The defect grade is determined by a relationship between the largest defect in the symbol and
the symbol contrast. The smaller the defect, the better the grade.
(In general, a small aperture used to analyze very wide elements will cause the largest
defects.)
The Inspector 4000 incorporates a feature that trims reflectance data gathered during a scan
to approximately 10 times the X dimension (5X after a UPC/EAN addendum). These areas,
on either side of the bar-code, are assumed to be quiet zones and are included in the analysis.
A graphic object in the quiet zone will produce an “F” grade. This indicates a quiet zone
that is too narrow. We recommend that you scan in both directions to make maximum use of
this feature.