View Cart|
|
|||||||||
|
|
|
|
|
|
View Cart |
|||
|
Bar Code Knowledge BaseThe Barcode-Store.com Knowledge
Base is a growing inventory of information and answers to Frequently Asked
Questions on bar code related topics. If you have bar code related questions
that aren't answered here, or if you'd like to suggest an addition to this
section, please feel free to give us a call. One of the most common questions we get is regarding different cable interfaces. Here are the most popular types.
Data Collection: Glossary of Terms
Alphanumeric - The character set that contains letters,
numbers, and usually other characters such as punctuation marks. ANSI - The American National Standards Institute, a
nongovernmental organization responsible for the development of
voluntary standards. Aperture - The opening in an optical system that establishes
the field of view. ASCII - The character set and code described in American
National Standard Code for Information Interchange, ANSI X3.4-1977.
Each ASCII character is encoded with seven bits. The ASCII character
set is used for information interchange among data processing systems,
communication systems, and associated equipment. The ASCII set
consists of both control and printing characters. Aspect Ratio - In a bar code symbol, the ratio of bar height
to symbol length. Bar - The darker element of a printed bar code symbol. Bar Code - An automatic identification technology that
encodes information into an array of adjacent varying width parallel
rectangular bars and spaces. Bar Code Character - A single group of bars and spaces that
represents a specific number (often one) of numbers, letters,
punctuation marks, or other symbols. This is the smallest subset of a
bar code symbol that contains data. Bar Code Density - The number of data characters that can be
represented in a linear unit of measure. Bar code density is often
expressed in characters per inch. Bar Code Label - A label that carries a bar code symbol and
is suitable to be affixed to an article. Bar Code Reader - A device used to read a bar code
symbol. Bar Length - The bar dimension perpendicular to the bar
width. Also called bar height. Scanning is performed in an axis
perpendicular to the bar length. Bar Width - The thickness of a bar measured from the edge
closest to the symbol start character to the trailing edge of the same
bar. Bi-directional - A bar code symbol capable of being read
successfully independent of scanning direction. Check Character - A character included within a string of
data whose value is used for the purpose of performing a mathematical
check to ensure the accuracy of that data. Check Digit - A check digit serves the same purpose as a
check character, but it may assume numeric values only. Concatenation - The ability of a reading system to join
together the data from multiple symbols and interpret it as a single
message. Decoder - As part of a bar code reading system, the
electronic package that receives the signals from the scanner,
performs the algorithm to interpret the signals into meaningful data,
and provides the interface to other devices. Depth of Field - The distance between the maximum and
minimum plane in which a code reader is capable of reading symbols of
a specified X dimension. EAN - European Article Numbering system, the international
standard bar code for retail food packages. Film Master - A photographic film representation of a
specific bar code or OCR symbol from which a printing plate is
produced. First Read Rate - The ratio of the number of successful
reads on the first scanning attempt to the number of attempts.
Commonly expressed as a percentage. Abbreviated as FRR. Font - A specific size and style of printer's type. HIBCC - The Health Industry Business Communications
Council. Input Device - That portion of a bar code reading
system that employs electro-optical techniques to determine the
localized reflectivity of a symbol. Intercharacter Gap - The space between two adjacent bar code
characters in a discrete code - for example, the space between two
characters in Code 39. Interleaved Bar Code - A bar code in which characters are
paired together using bars to represent the first character and spaces
to represent the second, e.g., Interleaved 2 of 5. Laser Scanner - An optical bar code reading device using a
low energy laser light beam as its source of illumination. LED - Light emitting diode. A semiconductor that produces
light at a wavelength determined by its chemical composition. The
light source often used in light pens. Light Pen - In a bar code system, a handheld scanning wand
that is used as a contact bar code reader held in the hand. See Wand
Scanner. Mil - One one-thousandth of an inch (0.001"). Misread - A condition that occurs when the data output of a
reader does not agree with the data encoded in the bar code
symbol. Module - The narrowest nominal width unit of measure in a
bar code. Multidrop - A network topology in which multiple devices,
each with a unique address, are connected to a common set of data
communication lines. Nominal - The exact (or ideal) intended value for a
specified parameter. Tolerances are specified as positive and negative
deviations from this value. Numeric - A character set that includes only the
numbers. OCR-A - An abbreviation commonly applied to the character
set contained in ANSI Standard X3.17-1981. A stylized font choice used
for Traditional OCR printing. OCR-B - An abbreviation commonly applied to the character
set contained in ANSI Standard X3.49-1975. A stylized font choice used
for Traditional OCR printing. Orientation - The alignment of a bar code symbol with
respect to horizontal. Two possible orientations are horizontal with
vertical bars and spaces (picket fence) and vertical with horizontal
bars and spaces (ladder). Port Concentrator - A piece of data communication equipment
that allows several different connected devices to transmit data to or
receive data from a single master communication port. POS - Point of sale. Postnet Code - A symbology used primarily by the U.S. Postal
Service for mail sortation. All bars and spaces are the same width.
ZIP Code information is encoded into the particular arrangement of
tall and short bars. This is a ``height modulated" symbology. Pre-Printed Symbol - A symbol that is printed in advance of
application either on a label or on the article to be identified. Print Quality - The measure of compliance of a bar code
symbol to the requirements of dimensional tolerance, edge roughness,
spots, voids, reflectance, PCS, quiet zone, and encodation. Quiet Zone - A clear space, containing no dark marks, that
precedes the start character of a bar code symbol and follows the stop
characters. Sometimes called the ``clear area." Reflectance - The ratio of the amount of light of a
specified wavelength or series of wavelengths reflected from a test
surface to the amount of light reflected from a barium oxide or
magnesium oxide standard under similar illumination conditions. Resolution - In a bar code system, the narrowest element
dimension that can be distinguished by a particular reading device or
printed with a particular device or method. RFDC - Radio Frequency Data Collection. Manufacturers of
RFDC equipment include Teklogix and Symbol. Scanner - An electronic device that electro-optically
converts optical information into electrical signals. Self-Checking - A symbology is termed self-checking if a
single printing defect will not cause a character to be transposed
into another valid character in the same symbology. Space - The lighter element of a bar code usually formed by
the background between bars. Symbol - A combination of bar code characters (including
start/stop characters, quiet zones, data characters, and check
characters required by a particular symbology), that forms a complete,
scannable entity. Traditional OCR - The first form of two-dimensional OCR
developed, using the stylized OCR-A and OCR-B fonts. Uniform Container Symbol (UCS). Uniform Code Council (UCC) - Previously the Uniform Product
Code Council; the organization that administers the UPC and other
retail standards. Universal Product Code (UPC) - The standard bar code symbol
for retail food packages in the United States. UPC-A - A UPC symbol encoding a number system character, 10
digits of data, and a check digit. UPC-E - A UPC symbol encoding six digits of data in an
arrangement that occupies less area than a UPC-A symbol. Also called a
``zero-suppressed" symbol because a 10-digit UPC-A code can be
compressed to a six-digit UPC-E format by suppressing redundant
zeros. Uniform Symbol Specification (USS) - The current series of
symbology specifications published by AIM; they now include
USS-Interleaved 2 of 5, USS-39, USS-93, USS-Codabar, USS-128, USS-49,
and USS-16K. Wand Scanner - A handheld scanning device used as a contact
bar code or OCR reader. X Dimension - The nominal width dimension of the narrow bars
and spaces in a bar code symbol.
QUESTION: I've heard the phrase "two up" used. What does that mean? ANSWER: It refers to the number of labels across the width of the roll. EXAMPLE:
QUESTION: When you describe a label size (ie., "4x6"), which number represents the height, and which number represents the depth? ANSWER: The first number (the "4") represents the height, and the second number (the "6") represents the depth. EXAMPLE:
QUESTION: What is the standard spacing between labels when they are still on the roll, and what does the "core size" mean? ANSWER: The standard spacing between labels when they are still on the roll is 1/8th of an inch, and the "core size" refers to the diameter of the roll on which the labels are wound. EXAMPLE:
QUESTION: What are "Direct Thermal" labels? ANSWER: Direct Thermal labels are printed on a material that reacts to the heated impact of a direct thermal imaging device. The label has a special coating that turns black when the heated pins of the thermal printer strike it, leaving a mark on the paper. Several different coatings are available. It is important to match the coating to the imprinting device for optimum performance. Our sales force will be happy to assist you in your selection of the appropriate materials for your machine. QUESTION: Does the use of "Direct Thermal" labels have any effect on the life of my bar code printer's print head? ANSWER: Yes. With the Thermal Direct method, the print head is in "direct" contact with heat sensitive paper (i.e. labels), and no ribbon is used. As a result, consumable costs are lower (i.e. no ribbon is consumed), but the print head undergoes SUBSTANTIALLY MORE wear and tear. The smooth wax-resin ribbon produces far less friction than paper, so a print head lasts approximately FOUR TIMES LONGER when printing in Thermal Transfer mode versus Direct Thermal mode. Print heads should be and are considered consumable items - and they add considerably to the overall cost of producing a label. QUESTION: What are "Thermal Transfer" labels and how are they different from "Direct Thermal" labels? ANSWER: Thermal Transfer labels (or indirect thermal) are similar to Direct Thermal labels except for the coating of the material. Thermal Transfer products rely on a coated ribbon in the printer to create the black markings. Thermal Transfer ribbons are available in several different technologies. They can be resin, hard wax, soft wax or other configurations. As in Direct Thermal, the match of ribbon/label material is important to performance. Consultation with our sales force will assure the correct product mix to achieve the combination of quality image and best value/lowest price to serve your needs. Bar Codes: Frequently Asked Questions What is a Bar Code? Bar code 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 Bar Code? Bar codes are accurate. They eliminate manual data entry errors. Research has shown that the error rate due to bar code misreads is less than one thousandth of one percent. Tests have shown that bar coded 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. Bar codes speed data entry. Even with a simple wand, a bar code 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. Bar codes can be produced easily and cheaply. Bar codes can be printed on most computer printers, for the cost of ink and paper. Even a low cost dot matrix printer can produce bar codes of adequate quality. How Does a Scanner Work? Scanners are the devices that read bar codes. 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 bar code 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 Bar Code Represent? No matter which bar code 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 bar code symbologies. In the typical format, each of the elements of the bar code 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 bar codes. They can be found on almost all general merchandise. There are over 24 bar code symbologies, but only about 5 are in common usage. Having said that, someone will dispute my number. Other than the ones listed below, there are 5-7 new symbologies that are attempting to replace the ones in use today. These new codes are good symbologies and will take their place in the ADC world, but it will take some time for them to become common in usage. These are the 2 and 3 dimensional symbologies that are being used for specific applications in the courier and transportation industries. UPC - As of today is the bar code you see in the grocery and retail stores. It is only used for POS in retail applications. The UPC bar code consists of 4 parts. The 1st number is the system identifier; next 5 digits are the manufacturers assigned number; next 5 digits are the manufacturer's own assigned product number and the last digit is the check digit. UCC/EAN- Code 128 symbology is used to identify products on shipping containers. There is a standard format for shipping container labels. The shipping Container Code also uses Code I 2/5 symbology for printing on corrugated containers. Code 39 or Code 3 of 9 is the most common symbology for printing bar codes for other uses than retail. It, and Code 128 are both alpha/numeric and very flexible. Codabar is still used by most libraries today but some are changing to C39. This is due to history rather than design. Codabar was the first symbology to be used by any group and libraries started using bar codes before the retail industry. The manufacturer's assigned number has to be issued from;
Elements of Bar Code No matter which symbology you will be using, all bar code 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 bar code 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. 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. Bar code 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 bar code
Discrete symbologies consist of unique bar and space patterns for each
character. Continuous codes cannot be separated into individual characters.
ITF is a continuous bar code. 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 bar code. 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 å11 is a wide bar or space
and å01 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. 1 + 1 + 2 + 1 + 5 + 1 + 2 + 3 + 5 = 21 30 is the next higher multiple of ten
30 - 21 = 9 the check digit = 9
In the POSTNET bar code the numbers to be encoded would be 311215123592. The
bar code reader reads 311215123592. Reading a check digit of 392 and
calculating a check digit of 392 from the other numbers it read, the bar code
reader now is doubly certain that the numbers were correctly decoded.
Bar code 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 Bar Code?
How small the bar code can be becomes a function of how finely the printer
can print and how fine of a bar code a reader can read.
Industry guidelines will strongly caution against undersizing bar codes. This
is good advice. There may be times when you want bar code 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 bar code against the
advantages of having smaller bar code.
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 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 scan 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 bar code 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. |
||||||||
