Guidelines for Creating a Good Bar Code

by Susan Snyder, Microscan Systems Inc.

Return to article: Bar Coding Rules

Successful applications all start with a good bar code. Following these five guidelines will eliminate unnecessary application challenges and will go a long way toward helping you achieve the 100% data integrity you desire from your data capture system. These guidelines apply to laser scanner applications.

Select an appropriate symbology. Before you decide on a specific symbology, make sure you are up to date on all applicable industry standards and specifications. For example, FDA, in its preliminary bar code mandate, has stated that only linear bar codes can be used on unit-dose packaging. Educating yourself will save you time and help you avoid headaches. 

When selecting a bar code, you should also choose one that is appropriate for your specific application. Even within industry standards and guidelines, there is often a provision for several options. Ask yourself these standard questions:

� What is the general purpose of the bar code?
� How much space is available?
� Will it be used inside your facility or will others need to read it as well?
� What type and how much data will you need to encode?
� What are your marking/printing requirements?

Make the narrow bar in your bar code as large as possible. After you have selected the symbology you are going to use and are starting to design your bar code, be sure to use the largest narrow bar size (X-dimension) possible. The X-dimension is the smallest bar (width) or space in your bar code and is used as a reference for determining the size scale of the bar code. 

By making the X-dimension as large as possible, you will save yourself time and money down the road. A larger bar code is easier to print and read accurately and will ensure a greater depth of field from the bar code reader. In addition to making it easier for the bar code scanner to read the code, you will most likely have more equipment options to choose from. There are a lot more scanners on the market that can decode a bar code with a 10 mil (0.010 in.) narrow bar than a 3.3 mil (0.0033 in.) narrow bar. 

Maximize your bar height. When designing your bar code, you should also maximize the bar height of the bar code as much as possible. Bar code height is important for ensuring reliability. It�s the built-in redundancy of a linear bar code. The taller the bar code, the more area the bar code reader has to scan the symbol. If part of the bar code is damaged, the scanner has a greater chance of still being able to read the symbol. Microscan recommends that the scanner receive a minimum of five scans of each symbol to achieve the optimal read performance possible from the bar code scanner.

Create the best contrast possible. Make sure you achieve the best contrast possible between the bars and spaces of your bar code. Good contrast creates a strong bar code signal, which makes it easier for the bar code scanner to differentiate between the bars and spaces of your bar code. This will make it easier for the bar code scanner to read the code as well as reduce the chance of noise interference. 

Don�t violate the quiet zone. The quiet zone is the space preceding the first bar and trailing the last bar in a bar code. As a general rule, this space needs to be a minimum of 10 times the width of the narrow bar in your bar code. The scanner will not be able to read the bar code if text or any other mark encroaches into this area. The quiet zone is the most frequently violated requirement in bar code applications. Even in applications where space is at a premium, such as the label on a syringe, text and artwork cannot encroach on this area or the bar code reader will not be able to read the code.  

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