What is Wrong with my Barcode?
Markus Winkler
Data storage takes several forms. A flash drive (USB, thumb drive, etc.) is a popular form. Hard drives, internal or external are another. Newspapers and magazines are yet another, and somewhat similar to barcodes in that they are portable data storage in the form of an image.
When barcodes do not work right, a methodical approach is helpful in sorting out the problem. Is the barcode working intermittently? Does it work on some scanners but not others? Is the captured data different from what is expected? Is the barcode not scanning at all?
Scanning Basics
Scanners capture barcode data by detecting reflectance differences of the bars and spaces. Bars or dots reflect less, spaces reflect more. Wide bars reflect less than narrow bars. The reflectance difference is how the data is stored and retrieved.
Barcode Basics
1D barcodes such as UPC and Code 128 look different from 2D barcodes like QR Code and Data Matrix, but they are similar in structure and function. Virtually all barcodes are arrays of elements (bars or dots and spaces) of various widths. The X dimension is the small element, the building block. Wide bars and spaces are multiples of the X.
Intermittent Scan Performance
Excessive print gain is usually the cause of barcodes that scan intermittently. Print gain causes bars to spread. Gain makes bars wider, robbing width from the spaces between them. The expected reflectance differences are affected; scanning becomes more difficult. Different types of scanners will respond differently. Camera-based scanners are generally more tolerant; CCD’s and lasers are generally less tolerant of gain.
In situations where the intermittency of a barcode is between a scanner and a smartphone, trust the scanner. Scanning with a smartphone is a meaningless and untrustworthy gauge of barcode quality.
Non-scanning barcodes
Several causes exist for barcodes that do not scan at all. Excessive gain can obliterate spaces, especially narrow spaces. When this happens the scanner does not detect the anticipated number of light and dark reflectance transitions, and data capture fails.
Scan failure results when barcodes have more than two reflectance values (light and dark). Common causes include patterned backgrounds and product show-through. Quiet zone encroachment also causes scan failure. Barcode placement too close to text, graphics, folds or edges of a package can result in scan failure. Likewise, creases or folds in shrink-wrap can render barcodes useless.
The Worst Problem
Barcodes that scan unexpected data are arguably the worst possible problem, because it is so difficult to detect. That familiar beep affirms—something. There are several reasons the data could be wrong. The problem could be an error in the lookup database—not a barcode problem at all. But the problem could be data transposition caused by a poorly printed barcode and an overly aggressive scanner.
Successful barcode scanning results from process control and a little bit of knowledge. Basic barcode training is not complicated, time-consuming or expensive. Customized barcode training is relevant, interesting and immediately applicable to your quality team and the important jobs they do.
Barcode Test
We do focused on-site and webinar-based training, tailored to your specific needs. Let’s work together to solve a barcode problem or prevent one from ever happening.
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John helps companies resolve current barcode problems and avoid future barcode problems to stabilize and secure their supply chain and strengthen their trading partner relationships.
