Despite
the complex nature of verification equipment it should be
simple to use and display the results in clear, easy to
interpret terms. The Verifier should be the bar code expert
in your organization, removing the burden of knowledge from
your staff.
If the format of the bar code is incorrect, the size too
large or too small or the print quality unacceptable, the
symbol will fail to scan. The supply chain is broken. The
number needs to be entered manually – perhaps incorrectly.
A customer incorrectly charged. Wrong goods ordered or
dispatched.
In
many cases a poorly printed barcode is worse than no bar
code at all.
Why
Verify?
Bar
code quality is vital, as every time a bar code fails to
scan, costs are incurred. At best the data is required to be
input manually whilst at worst deliveries are rejected.
A
recent survey by the e-centre (EAN UK) put the cost of poor
quality bar codes at over £500 million. Until recently,
many retailers have accepted these costs as a ‘fact of
trading life’. However, an ever increasing number of major
retailers are now taking a very different approach by
passing these costs back to suppliers. Goods are returned
and fines imposed. For repeat offenders the ultimate
sanction can be, and has been, delisting as a supplier.
Insurance
At its most basic level, verification is an insurance
policy helping to assure you that your bar code will scan
first time at all levels in the supply chain, thus enhancing
your supplier/customer relationship.
But
it’s more than that. As part of an effective QA system it
can help you win business. Are your competitors using
verification? Are they questioning the quality of your bar
codes with your customers? Is it affecting your business?
Why
Can’t I Just Use A Scanner?
Scanning
is no substitute for verification as no two bar code readers
are identical. They vary from wands to lasers to cameras,
from manually operated to automatic. Ambient light will vary
as will the distance of scanning. A bar code that is
‘checked’ with a wand gives no guarantee that it will be
readable with another wand, let alone a laser based unit.
A
verifier is a scientific device, taking precise measurements
of each individual bar and space and the amount of light
reflected from each. More advanced units will automatically
identify the symbology and magnification, check data
structure and validate the content as well as providing
diagnostic information. It is all very well knowing that
your bar code is incorrect but a verifier must be able to
identify the problem to allow you to take the necessary
corrective action.
Why
was the ISO/CEN/ANSI method introduced?
Prior
to the Current ISO standard of verifying printed bar code
symbols, only two factors were taken into consideration:
•
Dimensional accuracy of the bars and spaces.
• Reflectance values of the bars and the background (PCS).
This
traditional method would have been a reasonable way of
assessing the print quality, except that there was no agreed
way of determining where bar edges actually were or how and
where reflectance measurements should be made. As well as
this, bar codes were being measured with differing beams of
light (apertures). Both of these factors resulted in a wide
variation of results between verifiers.
With
the variety of uses for bar codes and the wide range of
printing techniques used, it was felt that a more scientific
approach was needed. In particular it was noted that
different scanners and the differing environments in which
these were used resulted in some aspects of poor print
quality being more significant than others. Simple
reflectance measurements were also found not to be helpful
when the contrast might vary within the symbol. A definition
of where a bar-space transition actually occurred was
required as were specific aperture sizes dependent upon the
symbology and size of bar code.
These
were then the main elements of the method that was initially
written up as an ANSI standard. This was then adopted by CEN
and eventually became an ISO standard. A Scan Reflectance
Profile (an analogue graph of the reflectance values of a
defined wavelength of light from a bar code symbol across a
scan path) was to be analysed and specific measurements made
from this profile in order to grade the scan. It was also
specified that a single scan was not enough for an overall
symbol grade to be decided and scans should therefore be
taken at up to ten different heights within the symbol. The
average of these results then becomes the overall symbol
grade.
This
method has proven to be a thoroughly scientific approach but
one that is also accepted and generally understood by users
of bar codes throughout the world. The grading method is
also easy to understand and different grade requirements can
be set for various applications of bar code technology
without the method needing to change. In recent testing of
verification equipment from various manufacturers, the
method has also proved to solve the main problem with the
traditional approach, as it was found that different pieces
of equipment gave the same results when applied to reference
symbols.
What
is checked/ what is not checked?
|
Checked |
 | Reflectance |
| Contrast |
| Decode |
| Light margins |
|
| Bar gain |
| Defects |
| Check Digits |
|
|
Not Checked |
| Human readables |
| Location |
| Height |
|
| Truncation |
| Orientation |
|
|
Advanced Checks |
| Magnification (X
Dimension) |
| Wide to Narrow Bar
Ratio |
| Application
standards
(Coupons, variable weight, etc...) |
|
| UCC.EAN-128 data
validity |
| RSS Data validity |
| Full encodation |
| Integral check
digit |
| Data format |
|
Case
study: What are the common problems with on-demand printers
?
As
the number of people printing outer case bar codes on-demand
has increased, so has the number of product rejections. The
vast majority of these are a small number of basic print
quality issues on thermal printers that should be identified
prior to dispatch and which should never have been allowed
to enter the supply
chain.
