We are bar coding our products and some customers are having trouble reading the codes, although they read successfully with our reader. We are told we need to verify the codes - what does this mean ?

Requirements for the checking and verification of bar codes vary depending on how the bar codes you have printed are going to be used. If you are printing bar codes purely for internal use and there will be no requirement for anybody outside your company or organisation to read them ("closed" systems) then just checking that the bar code encodes the correct characters and that these can be correctly read by your chosen reading equipment may well be perfectly adequate.

However, if you are producing bar codes that will be used by third parties, maybe on a variety of potentially unknown readers and scanners ("open" systems), then you may need to go a stage further. This is particularly the case in the retail environment where some larger store chains sometimes impose penalties on suppliers if they supply goods with unreadable codes. Here the requirement is to verify that the bar code has been printed in line with the "rules" of the symbology you are using and that the print quality meets specifications.

Verification is a more complex process than simple checking and requires special equipment capable of scanning your bar code and analysing the compliance of the code in line with the rules of the symbology. Usually it is necessary to purchase a specific bar code "verifier" to do this job. Verifiers can usually provide lots of very technical information about a bar code (e.g. contrast ratio rating, wide/narrow bar ratio etc). Normally the verifier will summarise all these technical measurements to inform the user if the code is within or outside the acceptable ranges of tolerance for the symbology concerned. Sometimes this is further summarised to a simple "good" or "bad".

Checking and verifying printed bar codes are not the same thing and it is important to understand the differences. The process of checking with a given reader does not necessarily mean that the bar code is correctly printed and readable by all scanners operating within acceptable tolerance ranges. However, the additional cost of validation may be prohibitive for some and, if you are confident that you are using a good quality printing source, simple checking may be adequate. You must however be prepared that one day someone will complain "we cannot read your bar codes". Responding that they work OK with your reader is not the same as having properly verified them!