Printronix T5000 Software Manual page 270

Chapter 7
Data Validation
7. Failure Message
Bar Code
Failure data is grouped into different types of failure, each of which defines a
bar code problem.
• Checksum: This occurs when the bar code is not properly encoded with
checksum digits.
• Decodeability: This occurs when the difference between wide and
narrow elements is too close to reliably discern. This is generally an
indication of an improperly set heat, speed, or pressure combination, or
the loss of heating element.
• Defects: This is a measure of unexpected dark spots in spaces or light
spots in bars. It is generally an indication of a poor ribbon or media
combination, a burnt pixel, or the printhead needs cleaning.
• Encodation: This occurs when the bar code is not properly encoded. For
example, a checksum is incorrect, a required number of characters is not
met, or required terminator characters are missing. This is usually an
indication of poor form or host application design.
• Internal Data Format Error: The bar code data format is invalid.
• PDF 417 Gap: This occurs when there are large gap damages (such as
ribbon wrinkle, voids, spots, etc.) within the PDF 417 data body code.
• Percent Decode: This is a measure of consistency throughout the height
of the bar code which indicates the number of good scans as a
percentage of total scans. This is usually an indication of large blemishes
within the code, such as with a wrinkle.
• Quiet Zone: This occurs when the minimum blank zone surrounding the
bar code has not been met. This can typically occur in poorly designed
forms where bar codes are placed too close to other elements, or the bar
code is too close to an edge of the media, or the position of the media is
shifting.
• (Symbol) Contrast: This occurs when the contrast between bars and
spaces is not sufficient. This can be due to excessively light printing from
too little heat on the printhead. It is also caused by colored media or
ribbons.
Modulation: This occurs when the ratio of the Minimum Edge Contrast
•
and Symbol Contrast is below 40%.
Minimum Reflectance: This occurs when the reflectance value for at
•
least one bar in a bar code is not half or less than the highest reflectance
value for a space.
Minimum Edge Contrast: This error occurs when the Minimum Edge
•
Contrast value is less than 15%.
In a bar code, each transition from a space to a bar (or a bar to a space) is
an edge whose contrast is the difference between the peak values in the
space and bar reflectance. Each edge in the bar code is measured, and
the edge that has the minimum contrast is the Minimum Edge Contrast.
270