Operator’s Guide Appendix C
002-5564 RJS, Minneapolis, MN
The parameter grade is determined by:
1. Calculating the edge contrast of every element
edge in a symbol
2. Finding the lowest value (minimum edge contrast)
3. Comparing it to a fixed threshold in the
specification (15%)
If the value is at least as great at the threshold, the
grade is “A,” otherwise the grade is “F.”
Symbol Contrast
This parameter can be graded “A,” “B,” “C,” “D,” or “F.”
Symbol contrast is the difference in reflectance values of
the “lightest” space (including the quiet zone) and the
“darkest” bar of the symbol (the greater the difference,
the higher the grade).
Note: Bar code colors can have a large effect on this
parameter.
Modulation
This parameter can be graded “A,” “B,” “C,” “D,” or “F.”
Modulation grade is based on the relationship between
the minimum edge contrast and the symbol contrast.
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.
Note: Aperture size has the greatest affect on
Modulation. The substrate material can also have a
major affect on Modulation.
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