Bar Code Scanning
Authored by: Niels Wartenberg and Susan Snyder; Microscan Systems Inc.
As with selecting a symbology, determining the physical requirements of the application will help determine which type of bar code scanner should be used for the most optimal results.
Selecting a Scanner
First, determine if the application requires a hand-held scanner or a fixed-position scanner. The easiest way to determine this is to answer the question: Does it make more sense to present the bar coded object to the scanner or the scanner to the bar coded object? Even applications that are typically thought of as hand-held applications are extremely successful applications for a fixed-position scanner. Depending on the object and the chemicals involved, it may be more convenient to place an object within the field of view of a fixed-position scanner than to pick up a hand-held scanner, maneuver it around until it reads the bar code, then set the scanner back down again.
What type of symbology will be used?
Consider what type of symbology will be used and the object it will be applied to. If the application calls for a linear black-on-white bar code printed on a thermal-transfer label, a wide selection of bar code scanners should be able to read it. If the application calls for a Data Matrix code etched onto a glass slide, an image-based reader will be required.
How far is the bar code from the scanner?
Another important consideration is the required distance between the bar code reader and the bar code being scanned. The physical distance, along with the X-dimension of the bar code, will determine the read range capabilities.
Is code placement consistent?
Are the bar code labels hand-applied or applied by a machine? Will the bar codes always be in the same location or orientation? The answers to these questions will help determine what type of scan pattern may be required.
What is the speed of the application?
The speed requirements of an application are determined by three factors: the speed the bar code is traveling past the reader, the bar code orientation (ladder or picket fence), and the row height of the bar code. Row height is especially important for bar codes in the ladder orientation. As a general rule, in order to ensure a good read on a symbol, Microscan recommends that the bar code reader obtain a minimum of five good reads on the label.
What are the environmental conditions?
Will the scanner be located inside a freezer? Will it need to read bar codes with condensation on the labels? Will it be exposed to chemicals? If the environment is particularly harsh, work-arounds can always be created to fit the needs of the application. For example, air can be blown on the bar code reader’s window to control the buildup of condensation.
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