Selecting a Bar Code

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Authored by: Niels Wartenberg and Susan Snyder; Microscan Systems Inc.

With so many different symbologies to choose from, it is easy to get overwhelmed trying to select the best bar code possible for an application. Before evaluating symbologies, first determine the objectives for the application.What does the bar code system need to accomplish?What function will it provide in the automation process? For example, a lab may need to determine the exact location of a specimen at any given time. Another objective may be to encode all relevant information into a bar code on reagent packs so that calibration and expiration date checking can be accomplished automatically.

Next, research all industry standards relevant to the application. Many industry associations have already selected a specific symbology or family of symbologies for certain applications. Some specifications are very general and simply recommend a symbology for a specific application. Other specifications are very detailed, specifying the density, row height, and additional formatting guidelines.

If there is not a standard that applies to the application, then determine the requirements and limitations of the application. First evaluate the physical requirements: How much real estate is available for the bar code? For the bar code reader? Table 1 provides the physical parameters of many standard bar codes. Next, select the required information to be encoded into the bar code. Will the data be numeric only, or will alphanumeric characters be required as well?

Table 1. The physical parameters of common linear and stacked bar code symbologies
7.5 mL Character length Code 39 Code 93 12 of 5 Codabar Code 128 UPC PDF 417
10 characters 1.5" 0.98" 0.7" 1.05" 0.7" 0.75" 0.69" (1 column) 0.95" (3 column)
20 characters 2.75" 1.7" 1.35" 1.92" 1.15" N/A  
50 characters 6.5" 3.78" 3.25" 4.5" 2.45" N/A 0.69" (1 column) 0.95" (3 column)
Check digit X X X X X X X X
Numeric X X X X X X X X
Alphanumeric X X     X   X X

Evaluate the materials to be used. Will the code be applied directly to the object, or will the bar code be printed on a label first? What type of environment will the media need to withstand? Last, based on the real estate available, select a bar code element size (narrow bar). This dictates the overall physical size of the bar code. While selecting a narrow bar code width, evaluate the physical parameters of each of the symbologies under consideration to determine which one will meet the needs of the application.

Before a final decision is made, think about the future. Will the symbol need to contain more data in the future? Will the selected hardware or media meet future needs? For example, will new tests be added, imposing new environment demands on the bar code labels? When possible, try to meet the needs of tomorrow’s applications at the same time. For example, if a lab is implementing a linear bar code system today, but plans to transition to matrix codes in 2 to 3 years, it may be more cost-beneficial to purchase imagers instead of laser scanners. While laser scanners may be less expensive, imagers can read both linear and 2D matrix codes, saving the lab the additional time and expense of replacing the laser scanners down the road.

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