Reading Bar Codes

Reading a barcode requires three decisions -- the input device, the decoder, and the interface -- with the input device (wand, CCD, or laser) having the greatest impact on system usability.

Once you have a barcode in hand, you must read it and process the information. Reading barcodes requires three basic decisions. You must decide on the input device, the decoder, and the interface. The input device reads the barcode and transmits the data to the decoder, which converts the data to ASCII characters. The interface is the connection between the decoder and the computer.

Input devices (wands, CCDs, badge scanners, and lasers) are the direct point of contact between the user and the barcode. No other choice you make will have a greater impact on the usability of the system. Naturally, there are several choices across a range of prices. In general, more expensive devices give better performance, but this is not automatically the case. The choice of input device is governed by these factors:

• Volume: Some input devices are inherently more usable and reliable than others. If you have a low-volume application, almost any input device will probably work well for you. A high-volume operation will generally be better served by a high-grade input device. High-grade input devices are fast and reliable.
• Barcode Quality: One advantage of high-grade input devices is their ability to read low-quality barcodes. In applications where barcodes are poor quality to begin with, or are likely to become damaged, using high-quality input devices can save time and reduce errors.

To select an input device, you must weigh all of these factors together. Once you have made a tentative decision, test the system under as many real-world conditions as you can simulate.

Get the input device a little dirty, damage some barcodes, print labels with a slightly worn ribbon or cartridge, test with an untrained employee, and try to anticipate other problems that may arise during normal operation. This way, you can be confident you have made the right choice. The most common input devices are:

• Wands: These are the least expensive input devices available ($140 to $180). They work well for low-volume scanning but have some disadvantages. They require a relatively flat surface, a fairly high-quality barcode, and some skill on the part of the operator. However, in applications where someone must scan one barcode from a sheet full of barcodes, wands are a good choice.
• CCD (Charge-Coupled Device) Readers: These are the next step up from wands ($400 to $600). A CCD has a read head the same width as the barcode (2 to 4 inches). The user places the head of the reader on the barcode, and a series of LEDs scan and read it. This requires less skill than a wand, and it will work with most low-quality barcodes. CCDs still require a relatively flat surface, and must be within 1/4" (0.5 cm) of the barcode to read it. The surface can be slightly curved in the direction of the bars, but no more than roughly the curve of a 1-liter bottle.
• Laser Scanners: These are the best type of input device and, accordingly, the most expensive ($400 to $1,300). They work with curved or uneven surfaces and will read most very low-quality barcodes. They also read over a much greater distance than wands or CCDs, usually 5" to 27" (12 to 65 cm). Laser scanners come in general-purpose and heavy-duty versions.
• Fixed-Mount Laser Scanners: These systems use laser readers that are fixed in place, with barcodes brought to the scanner. The most common example is the scanners used in grocery stores. Another example is a conveyor controller that reads labels on boxes or packages as they move down a line. These are used in the airline industry to process baggage, in warehousing to control conveyors or other equipment, and in many types of manufacturing.
• Slot Scanners: Slot scanners are used for time-and-attendance, security, and other systems. Each scanner has a slot through which you slide bar-coded cards. These scanners resemble the credit card readers seen in retail settings, but they read barcodes instead of magnetic stripes.
• Combination Scanners: You can frequently mix two different types of input devices. For example, you can attach a slot scanner and a laser scanner to a single decoder, allowing users to enter information either way. Percon's PowerWedge 20 dual model is one such device. Many models also let you attach magnetic card scanners to barcode readers, allowing you to process credit or ATM cards with the same system that reads barcodes on packages.