When talking about ensuring barcodes are correct, many people use the words validation and verification as though they are interchangeable – this is something that is not correct. Many companies that should know better promote their barcode reading systems as verifying barcodes when they are actually validating.
This is a very common barcode – a GS1 128 code that is encoded with a GTIN and a lot (or batch) number. Using the Barcode Check app on my phone I can get a very helpful validation report:
This is really useful because it shows me that my barcode meets the GS1 encoding spec and it confirms that the GTIN and lot number are correctly identified. This app also produces a report that can be saved or emailed.
While this is all very good – and I use this and similar apps all the time – validating the barcode does not show that it meets the GS1 or any other quality standard. It certainly won’t help when your large customer tells you that although your barcodes scan ok, they are not meeting the GS1 quality criteria. To ensure barcode quality, it is important to have a program in place to actually verify that your barcodes are meeting the quality standard.
For GS1 applications, there are clearly defined quality standards for each type of barcode that is allowed for that application.
As an example, here are the common barcodes GS1 allows for use in General Distribution (that don’t need to be scanned at POS):
I’ve left out a few of the allowed barcodes (the GS1 Databar codes) to keep the table size manageable – in my experience, most barcodes used in distribution (at least in North America) are ITF-14 and GS1-128, with UPC from time to time. Note that currently (late 2018), only linear barcodes are approved for these distribution applications.
As well as specifying barcode symbols the table also shows the maximum and minimum sizes for the barcode x-dimension (width of the smallest bars) and height, as well as the minimum quiet zone (clear space) that needs to be positioned at each end of the barcode. The final column in the table specifies the minimum quality specification that the barcode is required to meet – in each case, it is defined as 1.5/10/660. In the remainder of this article, we’ll look at what these numbers mean.
In the GS1 system, linear barcodes are verified against the ISO/IEC 15426-1 standard.
The standard grades a number of the barcode parameters and returns a single score – in the case of the GS1 distribution barcodes (with one exception) that score is 1.5.
The verification process inspects a number of parameters and assigns each one a grade between 0.0 and 4.0.
- Minimum Reflectance
- Reflectance margin
- Symbol Contrast
- Minimum Edge Contrast
The standard recommends that 10 scans are completed for each parameter (across different parts of the symbol) and the score for that parameter is the average of the 10.
The lowest score for any one of the parameters is the overall score for that symbol – it is rounded to one decimal place.
In our GS1 example, the 1.5 represents the minimum passing score the symbol must achieve.
Aperture & Wavelength of Verification Device.
When verifying a barcode, the resolution of the inspecting device as well as the lighting in the area can have an effect on the results obtained.
In an effort to standardize the testing as much as possible, GS1 specifies two testing parameters.
- Aperture – this is the resolution of the device being used to inspect the barcode. The parameter comes from the aperture of the lens used in the old wand-type scanners. In a newer imager based verifier, it relates to the resolution of the image sensor.
For distribution barcodes, the aperture of the verifier should be 0.010″ (10 mil or 0.25mm).
- Wavelength – because ambient can make a big difference to barcode verification, keeping lighting more consistent is important. For GS1 verification, the verifier should illuminate the symbol with red light with a wavelength of 660 nanometers (nm).
An Exception to the Rule.
After all this attempt at standardization, there is an exception included in the GS1 specification.
When printing directly onto brown corrugated (using technologies such as inkjet, or flexo), the lack of contrast between the bars and the brown background material causes the verification score to be reduced and the 1.5 target to be unobtainable.
GS1 takes this into account by making the following statement: “For ITF-14 symbols printed on labels with off-set, thermal, or laser print with an X-dimension 0.495 millimetre (0.0195 inch), the minimum quality specification is 1.5/10/660. For ITF-14 symbols printed directly on corrugate or labels with an X-dimension greater than or equal to 0.635 millimetre (0.0250 inch), the minimum quality specification is 0.5/20/660”.
So our customers using FoxJet ProSeries printers to print the ITF-14 barcode on cases can verify against the less stringent target, as long as the x-dimension is is above 25 mils.
Why Go Through All This?
Obviously, the use of auto-identification of items in supply chains using barcodes depends on the codes being readable at every step. The use of the GS1 standards ensures that barcodes are printed consistently and anyone using barcode scanners that meet the same requirements should be able to read them with no problems – regardless of whether they are using brand new imaging scanners or have 20-year-old laser scanners in a warehouse.
For anyone shipping barcoded packaging, verification is the only way to know for sure the barcode is correct and that it will be readable.
I had a great example of this just yesterday – a label printed on one of our own labeling systems included a UPC code. I didn’t have a verifier handy or even an industrial scanner – just my trusty phone. I scanned the barcode with two reliable apps – one would read it easily, one not at all. Did my barcode meet the GS1 requirement? I have no idea! This wasn’t for a production job so not a big deal. On the other hand, if you are using barcodes for your product or secondary packaging, you never want to be in that uncertain position.
Want to Learn More?
If you want to learn more about the various barcodes and how they are used in the GS1 system, you can download our GS1 Barcode Intro. Also, our ID Technology team is always ready to help you make sure that you labeling and barcode operations meet all your customer’s and GS1 requirements. Contact us today at 888-438-3242 Option#3 or contact David Holliday at firstname.lastname@example.org. We can help you sort through the details and be on your way to labeling and coding your products with confidence.
Source: Labeling News