Barcode Reading and Accuracy

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Barcode Reading and Accuracy

Barcode translation
Barcodes use different sets of international standards to encode data as a series of white and black bars. The barcode symbology is also used to define the technical aspects of the coding of any particular type of barcode, such as the width of the bars, character sets, data encoding, and checksum specifications. The capabilities of each barcode symbology are often uniquely suited to the purpose or use it was designed for. Table 4 provides examples of barcodes.
Table 4. Barcode Examples.
Barcode TypeExamples
Numeric only
  • PostNet - Used by the United States Postal Service (USPS) for mail sorting
  • Universal Product Code (UPC) - Used for most retail goods
  • Code 128 - Widely used; high reliability
  • Code 39 - General use code; very wide number of uses worldwide
  • Data Matrix - Large data holding capacity; good for specialized uses
  • Quick Response (QR) Code - Used for material control and order confirmations; limitless applications
Barcode scanning
A barcode reader or scanner uses a photo sensor to convert the barcode to an electrical signal by measuring the width of the bars and spaces. It then translates the different patterns into characters that are readable by a computer. Every barcode begins with a special start character and ends with a stop character. Some barcodes may also contain a checksum character. This is an accuracy verification function performed by the reader's decoder, which generates a calculation and then compares the two values to make sure they match. If there is a mismatch, the scan is discarded and the reader throws out the data and re-scans.
Barcode accuracy
Accuracy is one of the most convincing selling points for using barcode technology in laboratory applications. Studies indicate that even the best-trained data entry operator will make an error approximately every 300 keystrokes. In comparison, even the simplest barcode has an error rate of not more than 1 error in 394,000 scans. Table 5 summarizes the "worst case" accuracy rate for various barcodes.
Table 5. Barcode Accuracy Rates.
Barcode Type"Worst case" Accuracy Rate
Data Matrix1 error in 10.5 million
Code 128 1 error in 2.8 million
Code 391 error in 1.7 million
UPC1 error in 394,000