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Barcode verification failure

This article details the reasons for bar code failure. The titles below follow the sequence of the Bar Code Verification Report you have received from us, look for the headings with the crosses on your report.

  • Does NOT meet all EAN.UCC guidelines and ISO grades
  • Omni-directional Retail point of Sale
  • Automated Scanning (General Distribution)
  • Complies with EAN.UCC Location Recommendations
  • ISO Grade (0.0 - 4.0)
  • Scan Rate
  • Business Critical Comments
  • Magnification
  • X-dimension
  • Bar code Height
  • Quiet Zones
  • GTIN Check Digit
  • General Representation
  • Overall ISO Grade
  • Decode
  • Symbol Contrast
  • Minimum Reflectance
  • Edge Contrast
  • Modulation
  • Defects
  • Decodability
  • Physical Dimensions and Weight
  • Location
  • Bar Widths
  • Educational Comments

Does NOT meet all EAN.UCC guidelines and ISO grades
This is the overall result. To see why the sample failed, see the more detailed sections of the report.


Omni-directional Retail point of Sale
A cross here indicates that the bar code does not meet the requirements for scanning with the type of scanner used in supermarkets, service stations and a growing number of retail outlets in other sectors. These require a defined ratio between the height and width of bar codes as well as certain location requirements. Details will be given in following sections of the report.


Automated Scanning (General Distribution)
A cross here indicates that the bar code does not meet the requirements for scanning in warehouses and distribution systems that use the most basic forms of automated system that require the bar code to meet certain requirements of size, height, location. This is because simple automated systems have fixed scanners aimed 48mm up the side of units that move past them. Details will be given in following sections of the report.


Complies with EAN.UCC Location Recommendations
A cross here indicates that the bar code is not in the best place for easy scanning. Details will be given in following sections of the report.


ISO Grade (0.0 - 4.0)
A cross here indicates that the bar code does not meet the required grade on the ISO scale that assesses the adequacy of the reflective properties of the bar code and the "view" of it that a scanner can achieve. To improve the ISO Grade read the report for more specific details of individual measured parameters and correct any shortcoming that are identified.


Scan Rate
This indicates the result of a simple scan check performed with an ordinary scanner rather than the verifier, which is a scientific test instrument. Note: this is a non-scientific and unreliable test on its own. Scanners perform differently from each other so the fact that one scanner reads a bar code is not evidence that another will. Only a clear pass on a full verification test is evidence of that level of certainty. The ‘scan rate' is reported at the insistence of some major report users who wish to have an indication whether they can accept products with ‘failing' bar codes as a temporary measure while suppliers make changes to the bar code, or should decline the product altogether until changes are made.


Business Critical Comments
Any comments here are essential to improving the bar code enough to achieve a pass.


Magnification
A failure here indicates that the bar code is too big or too small. (Note that height is assessed separately from ‘size', which effectively refers to horizontal dimensions only). Magnification is expressed as a percentage of a ‘standard' or ‘nominal' 100% size. For details of required sizes see Bar Coding Basic User Guide (attached below).

  • To correct a magnification fault change the size of the bar code.

X-dimension
This refers to the width of the narrowest bars in the bar code and is an alternative way to express size. In most bar codes each bar and space should be the same width as the narrowest bar or precisely two, three or four times that width. For details of required X-dimensions see Bar Coding Basic User Guide (attached below).

  • To correct an X-dimension fault change the size of the bar code.

Bar Code Height
A failure here indicates that the bar code is truncated (too short). For required heights of EAN.UCC (i.e. retail) bar codes see Bar Coding Basic User Guide (attached below). ITF-14 and GS1-128 bar codes must be at least 32mm high to meet the requirements for all scanning environments they may enter and at least 13mm high to pass for hand scanning only.
Note that while it is possible to print a bar code too short they can never be printed too high. Printing over-height bar codes is best practice since it provides more scannable surface and aids rapid easy product handing.


Quiet Zones
(Also known as light margins) A failure here indicates that there is insufficient clear space down the indicated side of the bar code. Sufficient space is necessary to separate data in the bar code from spurious signals the scanner will generate as it crosses any contrasting colours in its range. Without sufficient separation the decoding software will be ‘confused' by incoherent signals that appear to be part of the bar code. Quiet zones should usually be 10x the X-dimension but see Bar Coding Basic User Guide (attached below) for quiet zone requirements on EAN.UCC (i.e. retail) bar codes. Note that the specified width is always a minimum: exceeding it is best practice.

  • To correct a quiet zone fault change the size of the quiet zone.

GTIN Check Digit
GTIN means Global Trade Item Number, the correct term for what is often incorrectly called ‘the bar code number' or - even more wrongly - just ‘the bar code'. The final digit in a GTIN is calculated and it serves an important technical purpose when the bar code is decoded. If the check digit is wrong the bar code will not decode. To correctly recalculate the check digit go to the check digit generator (located on the GS1 NZ website).

  • To correct a check digit fault recalculate the check digit.

General Representation
A failure for general representation means that something is wrong with one or more of the following:

  • The choice of symbology (i.e. type of bar code)
  • The match between the number in the bar code and the one printed below it
  • The bearer bars (only relevant to ITF-14 bar codes). Bearer bars may beprinted around any bar code and are recommended when any bar code isprinted on corrugated board. They are only required with ITF-14 bar codes printed with plates
  • The structure of the number involved
  • Whether the GTIN on the unit is the only one present.

The whole range of possible general representation failures is set out in GS1 General Specifications. Where a bar code fails for general representation an explanatory comment will be included in the ‘Business Critical' comments space on the front page of the report.

  • To correct a general representation fault identify and correct the fault.

Overall ISO Grade
A failure for overall ISO grade means that one or more of the individual parameters listed below has failed to meet the necessary ISO quality requirements.

  • To correct a failing ISO grade identify and correct the individual failing attributes

Decode
A failure for ‘decode' indicates that the although the verifier may have successfully decoded the bar code it does not assess the bar code as being of sufficient quality to be decodable by the full range of ordinary scanners in the market.

  • To correct a decode fault identify and correct the individual failing attributes

Symbol Contrast
A failure for symbol contrast indicates that the colour difference between bars and background is insufficient to provide scanners with a clear ‘look' at the bar code. Note that scanners use red light so they do not perceive colours as humans do. For example red is invisible to a scanner and appears white; green or blue will appear black unless printed in very light shades.
Bar codes must contain two contrasting colours - bars printed on clear transparent material will rarely work - and the bars must be a darker colour than the background. For illustrations of workable and unworkable combinations see Bar Coding Basic User Guide (attached below).
Possible reasons for failure:

  • Worn printer ribbon/toner etc.
  • Bar colour too light, ink too thin
  • Background too dark due to colour, recycled content, show-through etc
  • Ambient light (A symbol with inadequate contrast or reflectance may scan well in subdued light but less well or not at all in brighter conditions. This is unacceptable since a good symbol must perform in all situations.)
  • To correct a symbol contrast fault identify and correct the individual failing attributes.

Minimum Reflectance
An alternative means of expressing ‘symbol contrast,' minimum reflectance indicates whether the darkest features of the bar code are dark enough relative to the light features.
Possible reasons for failure:

  • Shiny label
  • Bar colour too light, ink too thin
  • Background too dark due to colour, recycled content, show-through etc.
  • Laminate or varnish on label
  • Ambient light.
  • To correct a minimum reflectance fault identify and correct the individual failing attributes.

Edge Contrast
This is a measurement of the sharpness of the bars i.e. is the edge of each bar crisp and clear, or is the colour patchy with poor definition of the bars?
Possible reasons for failure:

  • Inadequate symbol contrast
  • Inconsistent printing impression causing uneven strikes, halos etc.
  • Worn impact head causing loss of edge acuity, sharpness
  • Ribbon worn, dry, unevenly inked.
  • To correct an edge contrast fault identify and correct the individual failing attributes.

Modulation
Scanners and verifiers perceive the narrow spaces to be less reflective than the wide spaces so they are harder to "see" because they reflect less light. Similarly, the narrow bars in a symbol look less dark than the wide bars and are harder to see because they reflect more light than the wider bars do. This diminished intensity of narrow elements as compared to that of wide elements is called modulation. In simple terms the modulation grade reports how hard it is for the verifier to "see" whichever narrow space or bar it has the most trouble making out.
Possible reasons for failure:

  • (As for edge contrast or symbol contrast) or
  • Bar width reduction (BWR) factors - bars too wide, spaces too narrow
  • Texture of the substrate - usually too shiny to reflect light evenly from narrow spaces
  • Laminates, varnish or similar creating a shiny layer
  • Transfer/impression during printing - too much ink, thermal medium too hot.
  • To correct a modulation fault identify and correct the individual failing attributes.

Defects

A defect is a light spot in what should be a dark feature or a dark spot in what should be a light feature. A failure for defects means that the bar code has one or more flaw that may be "seen" by a scanner as a bar or space that should not be there.
Possible causes of failure:

  • Poor ink coverage due to pooling, absorption, splatter, bubbles, ‘ghosting' transfer heat, worn or damaged imaging tools
  • Print head defects - pits, chips, wear, burned-out elements in thermal media.
  • Substrate texture, recycled content, absorption (an apparently light background material may contain dark features discernible by scanners).
  • To correct a defects fault identify and correct the individual failing attributes.

Decodability
The test for decodability assesses each character in the bar code against the specification that defines the sizes of the bars and spaces that combine to make up that character. A failure indicates that the bar code contains at least one character that is so far outside the specification that a danger exists of ordinary scanners mistaking it for some other character or possibly not recognising it at all.
Possible reasons for failure:

  • Irregular bar width errors; wrong at origination or due to plate flexing or uneven inking
  • Manipulating the size of an electronic bar code image and distorting relative bar widths
  • Poorly dimensioned bars on plate
  • (In thermal printers) burnt out elements ‘shaving' bar edges
  • (In thermal printers) a mismatch between the width of print head elements and the width of bars the head is trying to print,
  • To correct a decodability fault, identify and correct the individual failing attributes.

Physical Dimensions and Weight
This information is or will be required for data synchronisation through GS1net.
Where data are present please check the details against your records. Consult the Product Measurement Guidelines and contact GS1 if after reading the guidelines you believe a discrepancy remains between the measurements taken by GS1 and those taken by you.

Location
Comments entered here indicate whether the bar code complies with GS1 recommendations as contained in GS1 General Specifications.

Bar Widths
A comment here will indicate whether the bar widths throughout the bar code are within acceptable limits. This will be helpful in assessing whether inaccurate bar widths have contributed to a specific failure.

Educational Comments
Comments in this space will indicate changes that are not essential but that will improve bar code quality. Their adoption is recommended.

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