Verification Basics

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Bar Code Verification Basics

What is bar code verification?
Determining the quality of the printed bar code against key parameters as defined by bar code specifications or industry specific applications.

There are three components to complete verification:

1 - Visual Inspection

Human Readable Numbers generally refer to the characters below or above the bar code and should match the size and placement set by published standards.
Quiet Zones are the clear margins to the left and right of the bar code.
Bar Code Location on the package should follow published guidelines or retailer requirements.
Bar Code Height is usually determined by industry standards and reducing the height of bar codes, called truncation, may cause complications with scanning the bar code at point-of-sale.

2 - Traditional Parameters: (based on bar and space widths as measured by the human eye)

Encodation checks that the bar code has the proper type (and number) of characters encoded in the symbol.
Print Contrast Signal looks at the difference in reflectivity between the bars and the spaces.
Average Bar Deviation represents the average amount of bar gain or loss throughout the bar code.
Quiet Zones are clear areas to the left and right side of the bar code that are required so that the scanning equipment will be able to determine where the bar code starts and stops.
Wide-To-Narrow Ratios apply to two-element width symbologies such as Code 39 and should follow defined ranges set by general symbology specifications or user-specific applications.
Check Character Calculations are performed to ensure the accuracy of the decode and is a result of a calculation performed on all characters preceding it.

3 - ISO/IEC Print Quality or ANSI Parameters: (based on bar/space reflectance values as measured by a scanner)

Symbol Contrast measures the difference of the maximum and minimum reflectance values of all the bars and the spaces in the bar code.
Modulation is the difference in the widths of bars versus spaces and the difference in reflectance values between wide and narrow elements.
Defects are reflectance irregularities in a bar code such as voids in the bars or spots in the space or quiet zones.
Decodability is a measure of the accuracy of the bar code compared against the appropriate reference decode algorithm and measures the amount of tolerance remaining for decoding.
Edge Determination counts the number of element edges which cross the global threshold line and checks if the count conforms to a legitimate bar code symbology.
Minimum Reflectance compares the highest reflectance value and the lowest reflectance value.
Minimum Edge Contrast measures the difference in reflectivity from a bar to an adjacent space or from a space to an adjacent bar.
Decode determines if a scanned bar code can be converted into a series of valid characters.
Symbol Grades range from A (Perfect) through F (Failing). The overall symbol grade is based on multiple scans (usually 10) of a printed bar code. A printed bar code with an ANSI grade of A should produce a high first-read rate. Most retailers will accept a Grade D or better on bar codes printed on corrugated boxes and Grade C or better on all other printed material. Please check with your retailers for their specific requirements.

Why can't I use a scanner to check if my printed bar code will scan at the register?
A scanner is designed strictly to decode or read the bar code. A scanner will not give any reliable indication of how well any other scanner can decode the bar code. Nor does it help you understand whether the symbol deviates from perfect and the specifics of the symbol's imperfections. Whereas, a verifier is a precision instrument that is specifically designed not only to decode bar codes but also to evaluate the symbol print quality against industry published standards.

Why verify?
As bar code applications become more and more critical to a company's success, the cost of bar code scanning failure becomes more significant. Such giant merchandisers as Wal-Mart, for example, have become famous for leveling whopping fines of $50,000 or more on suppliers whose product labels repeatedly misread. Consequently, bar code verification systems, once exclusively used by printers and label vendors, are now commonly used for on-site printing. Using a verifier to complete your bar code quality program will help to avoid financial loss of business or possible fines of $10,000 to $250,000 for non-compliant bar codes. Verification is the insurance that your barcodes will scan effectively and efficiently.
It is the responsibility of the 'originator' of the bar code symbol (usually the brand owner of the product being bar coded) to ensure that it meets the quality requirements of the entire supply chain.

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