Barcodes: What You Scan Is What You Get

Aug. 1, 2009
Efficiency and reliability are two reasons barcodes are prevalent in material handling.

The technical foundation of barcode technology originated in the 1940s with an effort to automate the checkout process in grocery stores. Interestingly, despite the enormous worldwide success and explosive growth of barcodes everywhere, the fully automated checkout remains the holy grail of automated data collection.

As an alternative to the traditional barcode “zebra-stripes” that we are all familiar with, the past decade has seen some evolutionary growth of non-directional radio frequency identification (RFID) solutions. RFID systems require electronic tags (either passive or battery-based active devices) and radio-frequency excitation/reading portals to activate and detect the presence of RFID tags within range. RFID's ability to find and read data packets from any tagged item or asset in close proximity offers advantages in certain applications; however, technical challenges still remain.

Barcode technologies have similarly marched forward with the development of linear and 2D code formats along with versatile printing and scanning technologies. This progress has allowed barcodes to maintain their utility for automatic data collection and inventory tracking.

Barcodes offer high-speed, reliable data collection and on-the-fly processing. Barcode label printers can generate fixed or variable barcode data (e.g., multiple batch production labels or individual sequential serial number labels). Similarly, barcode readers can scan thousands of items per hour with high accuracy. This allows a supply chain to boost production and packaging rates on the front end, accelerate material handling throughout the distribution channel and record end-user transactions at the far end.

A well trained data-entry clerk will typically make a single error once every 250 to 300 keystrokes. By comparison, worst-case barcode scanning operations generate an error an average of once every 500,000 scans. The latest generation of barcode formats and scanning equipment have error rates better than 1:1,000,000, and in some applications, better than 1:10,000,000.

Types of Barcodes

From baby formula to boogie boards, barcodes have universal reach. Virtually every consumer product sold today carries a UPC (Universal Product Code), a unique identifier that specifies manufacturer and product details. Beyond the consumer market, barcodes are all around us — from hospitals to manufacturing lines, driver's licenses to shipping boxes.

The technology that began decades ago as a graphical representation of Morse Code's dots and dashes has today evolved into more than 30 linear barcodes and, more recently, more than 40 2D barcodes capable of encoding additional data.

The most common linear barcode is the UPC, while other linear codes offer additional versatility, particularly in manufacturing applications for production lot and serial number tracking (Code-39) or postal applications (POSTNET).

Multi-dimensional (2D) codes came into vogue by an effort to increase the data density of barcodes, enabling them, for example, to encode complete delivery address information on shipping cartons. Two widely recognized codes are MaxiCode, originally developed by UPS, and PDF417, developed by Symbol Technologies (now owned by Motorola).

MaxiCode, although now in the public domain, is used by UPS worldwide to facilitate high-speed, automatic package sortation by encoding delivery address records of up to 93 alphanumeric characters.

PDF417 is used on driver's licenses, both here and abroad. Its name reflects its intended use: In this case, PDF stands for Portable Data File, and a full PDF417 implementation can encode more than 1,000 bytes of data.

Material Handling Applications

Barcodes work well with compact data records that can be generated and scanned at high speeds, facilitating rapid identification and tracking of material. Code geometries and advanced scanners are now position-independent and multi-directional, allowing high-speed readers to locate and interpret a barcode label anywhere within its field of view. This permits cartons to be scanned quickly without having to orient them in any particular position.

Contemporary industrial conveyor scanners are capable of processing thousands of scans per second; both UPS and FedEx have implemented automated conveyor package sorting systems that can scan up to 15 million packages per day.

Point and Shoot

One of barcode's strengths is its point-and-shoot characteristic: what you see — or rather, what you scan — is what you get. This advantage lends itself to challenging data collection applications.

Modern-day hand-held barcode scanners generally use either laser-based scanning or CCD imaging to capture raw barcode data. An integral microcontroller then completes the task of code interpretation and data conversion, typically providing either RS232 serial or keyboard-equivalent data that eliminates operator keyboard input. Scanner-generated data can support a variety of PC-based material handling applications.

Such applications tend to be complicated because a number of practical challenges come into play; for instance, sub-zero operation is often essential (such as in a cold-storage facility). This necessitates integral heaters for onboard computers and warming harnesses or heater-cups for hand-held scanners.

In addition to temperature, scanning range comes into play. A lift truck operator needs to be able to scan barcodes at a comfortable and practical distance. While a scanning range of 6 to 36 inches is effective in retail settings, it would hobble a lift truck data collection application.

Lift truck operators maximize efficiency by staying in motion, so a hand-held scanning range of 6 to 36 feet is required. This allows an operator to scan material, pallets or racks without disembarking, and a lift truck-mounted computer operating on a wireless network can provide immediate feedback, confirming right place, right material.

Much of the world's commerce involves large, heavy items that move by lift trucks rather than conveyor lines. With point-and-shoot laser scanners, a lift truck operator can receive pick-and-place instructions from a lift truck-mounted wireless networked computer and then scan and verify the pallet or container to ensure the correct material is moving to the correct destination.

Gregory J. Walker is the founder and president of Citadel Computer Corp., a manufacturer of industrial computers and barcode scanners.

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