Bar Code Knowledge Base
The 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.
Cable Interfaces
One of the most common questions we get is regarding different cable interfaces. Here are the most popular types.
Data Collection: Glossary of Terms
Labels: Frequently Asked Questions
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:
ONE UP
|
TWO UP
|
THREE UP
|
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:
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|
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;
- The Uniform Code Council in the USA
202 - 1009 Lenox Drive, Lawrenceville,
phone: (609) 620-0200 fax: (609) 620-1200 website: http://www.uc-council.org
1500 Don Mills Road, Suite 800,Toronto, Ontario, M3B 3L1
phone (800) 567-7084, fax (416) 510-1916 website: http://www.gs1ca.org/home.asp
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
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 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.
Human-Readables