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Glossary of data collection terms

Frequently Asked Questions - Bar Code Labels

I've heard the phrase "two up" used. What does that mean?
When you describe a label size (ie., "4x6"), which number
represents the height, and which number represents the depth?
What is the standard spacing between labels when they are still on the roll,
and what does the "core size" mean?
What are "Direct Thermal" labels?
Does the use of "Direct Thermal" labels have any effect on the life of
my barcode printer's print head?
What are "Thermal Transfer" Labels and how are they different from
"Direct Thermal" Labels?

What is a Barcode?
How Does a Scanner Work?
Why Use Barcode?
What Does the Barcode Represent?
Elements of Barcode
What is a Check Digit?
How Small Can I Make the Bar Code?
Readability vs scannabilty

Barcode is a pattern of bars and spaces which represent numbers, letters or characters.

Code 39, for instance, has a unique pattern. Code 3 of 9, as it is sometimes called, derives its name from the way in which the pattern is created. Each character has nine elements (five bars and four spaces) and three of them are fat.

Why Use Barcode?

Barcodes are accurate. They eliminate manual data entry errors. Research has shown that the error rate due to barcode misreads is less than one thousandth of one percent. Tests have shown that barcoded information had a throughput accuracy rate of 1 error in 10,000,000 characters. Compare that to keyboard entry error rates of 1 error in 100 characters.

Barcodes speed data entry. Even with a simple wand, a barcode can be scanned in a fraction of the time it takes to enter the information manually. CCD and laser scanners are also available for even faster data entry.

Barcodes can be produced easily and cheaply. Barcodes can be printed on most computer printers, for the cost of ink and paper. Even a low cost dot matrix printer can produce barcodes of adequate quality.

How Does a Scanner Work?

Scanners are the devices that read barcodes. A scanner shoots pulses of light. If it falls on a light area, a zero (0) is read. If it falls on a dark area, it reads a one (1). Scanning the barcode generates a string of zeros and ones. This pattern of zeros and ones represents the characters encoded. The scanner software, or firmware, translates or decodes the strings into characters.

The scanner must be able to shoot a straight line across the bars and spaces. The taller the bars the greater the angle and the greater the chances of getting a good reading.

The shorter the bars the less likely the scanner will be able to shoot a straight line through the bars and spaces.

What Does the Barcode Represent?

No matter which barcode is used, the information encoded in the bars and spaces may be displayed above or below the bars. Since this is the aspect understandable to us, the characters are referred to as human readables. The bars and spaces are readable by machine.

UPC (A) is just one of several barcode symbologies. In the typical format, each of the elements of the barcode symbol represent predefined information.

The system digit and the manufacturer number are assigned by the Uniform Code Council, Inc. for UPC (Universal Product Code) in the United States and Canada. UPC is a subset of EAN (European Article Number), the international product code standard throughout the rest of the world.

The product identification number is assigned by the manufacturer. The check digit is used to check the data that is read.

These are, perhaps, the most commonly used barcodes. They can be found on almost all general merchandise.

To apply for a manufacturer identification number call or write:

The Uniform Code Council, Inc.
8163 Old Yankee Road, Suite J
Dayton Ohio 45458
Telephone: (513) 435-3870
http://www.uc-council.org/

If your company is located outside of the United States or Canada, to find the location of the local EAN agency contact:

EAN International
International Article Numbering Association
Rue Royale 145
B-1000 Brussels
Belgium
Telephone: 32-2-227-1020
Fax: 32-2-227-1021
web site: http://www.ean.be/

Elements of Barcode

No matter which symbology you will be using, all barcode share elements that make up the symbol. These are the bars and spaces, the human readables, and the quiet zone. In addition, a symbology may be either Discrete or Continuous.

Bars and Spaces

The bars and spaces determine the pattern of the encoded data. Each symbology represents a different strategy behind the creation of these patterns such as: being as condense as possible, printing as easily as possible, being as easy to decipher as quickly as possible, etc.

Each barcode has slightly different quiet zone requirements. For example, the quiet zone of Code 39 is ten times the width of the thinnest bar/space or 0.25 inches, whichever is greater.

Human-Readables

The human-readable is the data represented by the bars and spaces printed as text for people to read. The actual data encoded here is 3*35353*2. The asterisks are not displayed as human-readables in this example.

The Quiet Zone

The quiet zone is the clear area (free from marks) before and after the bars and spaces. Having a quiet zone is as important to readability as the bars and spaces! Scanners need to establish values for the quiet zone before they can evaluate the bars and spaces. Reading the color and reflectance of the quiet zone establishes how the spaces will read and determines the difference between the spaces and the bars. Barcode cannot be read without a quiet zone.

Even though the quiet zone actually surrounds the code (the Bar/Space image), the clear area above and the below the Bar/Space image is not required for readability of most symbologies.

Discrete vs. Continuous barcode

Discrete symbologies consist of unique bar and space patterns for each character. Continuous codes cannot be separated into individual characters.

ITF is a continuous barcode. You cannot pull it apart into discrete, individual characters. Notice how the bars of the 3 and 5 are embedded in the bars of the 8 and 2.

Codabar is a discrete barcode. You can pull apart characters into discrete, individual units. The spaces between characters do not have critical dimensions.

The pattern of the number five is 310000102 where ć11 is a wide bar or space and ć01 is a narrow bar or space.

What is a Check Digit?

A check digit is used to check that the data is read correctly. Different symbologies apply different formulas to the encoded numbers to yield a single digit. That digit is the check digit. That check digit is usually added to the end of the already encoded numbers.

The computer checks that the numbers were read correctly by comparing the check digit it calculates against the check digit it read.

For example: When encoding the ZIP code 311215-12352 into POSTNET, the check digit is the total of the numbers subtracted from the next higher multiple of ten.

In the POSTNET barcode the numbers to be encoded would be 311215123592. The barcode reader reads 311215123592. Reading a check digit of 392 and calculating a check digit of 392 from the other numbers it read, the barcode reader now is doubly certain that the numbers were correctly decoded.

Barcode technology is millions of times more accurate than typing when it comes to entering information into the computer. Check digits make the systems even more accurate. Tests have shown that operators may do 10,000,000 entries between errors when using check digits.

How Small Can I Make the Barcode?

How small the barcode can be becomes a function of how finely the printer can print and how fine of a barcode a reader can read.

Industry guidelines will strongly caution against undersizing barcodes. This is good advice. There may be times when you want barcode as small as possible, however, this is only true until it becomes less readable. You must then weigh the difficulties that may be encountered when reading the barcode against the advantages of having smaller barcode.

UPC, EAN and JAN codes should never be used below 80% magnification. Even then this should be done only when the printing techniques are controlled and of sufficient resolution to get the tolerances necessary.

UPC, EAN and JAN codes should never be used below 80% magnification.

All of your work should be verified, especially at lower (smaller) magnifications.

Readability vs scannabilty

Readability is the measurement of how well the symbol is interpreted. scannabilty is a measure of the ease with which the scanner can decipher the symbol. For example, if two symbols were equally readable, a tall symbol is considered more scannable than a short one because there is a greater chance that the scanner will see the taller symbol.

Likewise, two symbols that are equally scannable may differ in readability due to the narrowness of the symbols or the quality of the printing.

The specifications that affect the readability and scannabilty of a symbol are width, color, printer dpi, bar width reduction, reflectance, and contrast. Symbol height only affects scannabilty.

In relation to retail checkout counters, first-scan readability is the ideal. In other words, the goal is for the scanner to be able to read the symbol the first time it is scanned. It does no good to create barcode that causes the checker to have to try over and over to read it. After a while the checker will stop attempting to scan your products. Worse yet, your products may be pulled from the shelves and returned to you if they don't scan easily. The goal is for the scanner to be able to read the symbol the first time it is scanned.