Selecting a barcode to suit the application

In many systems, it is probably going to be necessary to conform to a company-specified symbology. If this is the case, then the label or package printer will have no choice.

In other systems, the converter may be given the choice to use any symbology. In this case, the symbology must be chosen carefully and based on the factors set out in the list above, which are amplified in more detail below.

If the label or pack to be scanned is at the point-of-sale in a retail outlet or store then the UPC or EAN code, or a version of these as required, is the one that will generally need to be used. The code format and specifications are then as set out in the UPC or EAN code guidelines.

The UPC symbology, for example, has a standards committee that assigns manufacturer and product codes for well over one million products. That is the reason that a product manufacturer can put a barcode on a package without fear of duplication.

In terms of the character sets required in the barcode it should be determined whether numeric or alphanumeric codes are required. Numeric characters only will indicate that Interleaved 2 of 5, Codabar, UPC or EAN are possible. Alphanumeric characters will point to character sets such as Code 39, Code 128 or LOGMARS.

However, all symbologies have some limitations on the number of characters that can be encoded. UPC (Universal Product Code) is the most limiting. It is a numeric-only barcode that must consist of 11 digits. Furthermore, the value of these digits is determined by a grocery industry committee. Code 128 is the most flexible, with the full (128-character) ASCII set available.

The amount of space that is available on the label or pack for the code to be printed will also help to determine what code or code version can be utilized. If space is tight or limited then short form codes may need to be selected, e.g. Code 128, AN8 or UPC-E. Remember that the code height is not set out, but should be of a size that can be easily and accurately scanned each and every time.

It should also be noted that numeric-only barcodes such as Interleaved 2 of 5 can encode many more numbers in a given space than a more flexible symbology such as Code 128. This can often be critical in many cases. Even if one symbology is capable of making a barcode of the required size, it may still be possible to get a better first read rate using a different symbology. Note that some scanners, particularly wands, are built for a particular density. Make sure that the reading or scanning device matches the density of the barcode that will be used.

The type of material that the barcode is to be printed on can be a determining factor. Very high density codes will require a very smooth surface to be printed on to get the best and most accurately readable results. If the surface is a rougher material then a more suitable code type or density may be required. ITF for example, is great for corrugated materials.

What about colored codes or codes to be printed on a colored background? Barcode scanners virtually always use an almost monochromatic light source at the red end of the spectrum. Sometimes the light source is in the infra-red and invisible to humans which will mean that the best contrast will be obtained when the background reflects all the light and the bars reflect none. This is never fully achieved in practice but there must be a significant difference between the bars and background if the code is to be read reliably.

This means that wherever possible barcodes should be printed in black ink on a white background. This will give the best possible contrast over the widest range of conditions. If the barcode is likely to be scanned with an infra-red scanner (Figure 4.2) then the black ink must also be carefully chosen. Some blacks are transparent to infra-red – particularly those based on vegetable dyes.

A black ink based on a carbon pigment is likely to be suitable. 

However, in some situations, where for some reason or other it is necessary to use either a colored substrate for the background or a colored ink for the barcode, then the aim should be to stick to the following general rules.

Use light colored substrates towards the red end of the spectrum for the background. For the bars, use dark colored inks towards the blue end of the spectrum. Examples of which colored bars and backgrounds can and can’t be used are shown in the Figure 4.3.

In summary, using other colors for barcodes aside from the normal black bar on a white background should be highly discouraged. Though they may work when you test them with one particular scanner, other scanners may not be able to pick up on the different color variations, especially lower end CCD and laser scanners. It is best to stick with the standard black on white barcode label.

Many barcode applications will of necessity share common barcodes between many different vendors. If the label or pack printer is in a situation where some type of industry committee has set up standards, then it is most likely to be in their best interest to conform to that standard, even if it does impose other limitations.

Certainly, barcodes may need to be compatible with those of companies that the label or pack converter does business with. So whenever possible, use symbologies that are already in place.

A further factor to be considered is that some barcodes are inherently more readable than others. For example, tests have shown that Code 128 (one of the most flexible of all symbologies) is easily and successfully read by most readers - the symbology is better in nearly every way than the competition. In other cases, readability may be sacrified for some other requirement. So, always use the most readable symbology available, and test it using the actual equipment that will be used.

Finally, some symbologies are much more durable than others. Generally, those with better readability are more durable. It is recommended to always test barcodes by subjecting them to some abuse and making sure the reading or scanning equipment will still read them accurately and consistently.