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Barcode Basics – An Introduction

One of the main requirements of the production and manufacturing processes is the link between the information and the flow of materials, which increasing requires the implementation of Automatic Identification systems. Using barcodes, printed data can be easily and automatically read by means of reliable low-cost reading devices and barcode applications can be found in all fields of industry, retail, in the public sector and in every day life.

The information encoded in a barcode can be read automatically, using a barcode scanner or barcode reader, allowing for significant increases in the speed and accuracy of data transfer. The surrounding conditions can influence the reading and therefore the correct identification of the code.  It is therefore important to specify barcode reading equipment appropriate to the conditions including: speed, environment, barcode orientation and more.

For example, if specified incorrectly and products are “too close” it is possible that the wrong product may be diverted to the wrong location, or for packaging validation applications an incorrect product not identified resulting in Emergency Product Withdrawal (EPW) or Return to Manufacturer (RTM).

Barcodes can be found on moving objects, delivery notes, warehouse schedules, labels, etc., and wherever used it is essential the barcode is legible, and that the data within the barcode is correct.  Package Coding Management is the discipline for complete accuracy from design and data management to deployment and barcode validation.

A Guide - Bar Codes – Getting it Right – is available from the e-Centre on correct implementation of barcodes, common problems and how to achieve a good scan, every scan.

A number of useful links including links to the EAN, UCC and e-Centre are available from the Claricom web-site. (For more information visit www.claricom.com and select Communities)

This document is intended as a simple introductory guide on some Barcode Basic, including:

Linear (1D) Barcodes	European standards:	Choosing a Reading Device	2-Dimensional Barcodes	Typical Applications
Example Auto iD Codes	Common Terminology	Barcode Check-Digits	Glossary - Print Quality	Barcode Contrast

There are a number of different formats and symbologies of codes applicable to different uses and applications.

 

Linear (1D) Barcodes

Barcodes are a relatively recent technology and remain in continuous evolution. In the 1970’s and 80’ standard barcodes were developed and the most widely used have survived with European and world-wide standards.

European standards:

▪ EN 797 Barcode Symbology EAN/UPC
▪ EN 798 Barcode Symbology Codabar
▪ EN 799 Barcode Symbology Code 128
▪ EN 800 Barcode Symbology Code 39
▪ EN 801 Barcode Symbology Interleaved Code 2/5 (ITF)

EAN is the European standard in point-of-sale barcode identification with UPC codes being the American equivalent, while in industry, especially in materials handling, logistics and warehouse management, Code 128 and EAN 128 are increasingly used. It is predicted that Code 2/5 Interleaved (ITF) will, on the other hand, in the longer-term be replaced by Code 128 as the latter allows the encoding of more complex data-types and in an even more compact form.

Code EAN 128 is defined by the EN 799 standard. Full details about codes are available at www.ean-int.org.

2-Dimensional (2D) Barcodes

2D-Codes are based on two-dimensional representation of information.

This means that the standard barcode could be defined as a 1D-code but “stacked” to include a second information level in the Y-axis. By condensing information in this way the area necessary for a 2D-Code can be relatively small. With respect to standard barcodes, the implementation of two-dimensional reading technology leads to a limited increase in costs, provided that the structure of standard barcodes remains unchanged.

Matrix Codes

At a similar period in the late 1980’s and early 90’s a series of codes were developed which can no longer be defined as “barcodes”, but as Matrix Codes, the most common of which in manufacturing is now the Datamatrix code.

MaxiCode was specifically designed for omni-directional sortation of transport packages in a quick and reliable way.

In both Datamatrix and MaxiCode an error-correction algorithm is used to guarantee the reliability of data. A quick image-processing system reads codes by means of a linear camera or a matrix camera whenever necessary.

Data Matrix and MaxiCode are both omin-direction codes but Datamatrix is particularly useful in applications requiring small spaces. Data Matrix is very compact, reliable and can encode a great variety of characters and settings. This is considered a major benefit in the pharmaceutical sector, as well as in different manufacturing sectors.

Typical Auto iD Applications

EAN International and The Uniform Code Council are voluntary standards organizations. The EAN.UCC System standardizes bar codes, EDI transactions sets, XML schemas, and other supply chain solutions.  www.ean-ucc.org

For information on industry standards and EAN barcode allocation visit www.ean-int.org

For information on UCCnet and UPC barcode allocation visit www.uc-council.org

Examples of Barcode Applications

Retail application. The EAN-Code is read at checkout counters in supermarkets (POS = Point-of-Sale). Prices are looked up in the store’s or the checkout counter’s product database. In this field, the reading most commonly takes place by means of fixed-position POS scanners. In shops, on the other hand, a manual reader, such as a pen, a CCD-reader or a hand-held scanner may be used as it can be handled more easily.

Warehouse application. Transit barcodes are a material requirement for most warehouse, distribution and logistics systems; goods-in and goods-out movements are managed through computers and barcodes are used for speed and accuracy of data input. Product code numbers are processed thanks to barcodes and pen readers, and unattended fixed position barcode readers within the sortation systems at distribution centres.

Unattended Scanners are often used for automatic scanning in regional distribution centres and sortation systems. Typically mounted adjacent to product conveyors to read and validate barcodes which may, for example, be printed on cardboard boxes.  These scanners can read from distance and are used to either sort or re-direct product and confirm the product identification to the computer management system.

Validation Scanners are unattended barcode scanners also mounted adjacent to product conveyors, to confirm the barcodes are correct at the point of manufacture.  Warehouse and retail applications rely upon accurate legible barcodes.  Validation scanners can confirm that the barcode is legible, for example, that the barcode label is not damaged, and that the data contain within the barcode is a correct identifier for the product.

Common Terminology - 1D-Barcodes

A barcode symbol consists of a barcode and two “quiet zones”. The barcode includes encoded data, which consists of coloured bars and spaces. The quiet zone precedes and follows the bars and helps to identify the object to read/decode. Common terminology:

Choice of Barcode Symbology

Different barcode symbologies have been developed to meet different needs.   

In simple terms, the better the print quality and the higher the print contrast (bar to space) the easier the identification and decode of the barcode.

The code to be used is often selected from conflicting needs including:
▪ The data required; the amount of data or characters, and whether numeric or alpha-numeric
▪ The security or “self-checking” capability such as a check-digit
▪ The width of the decoding tolerances
▪ The density of the code; how much information can be encoded in a small space
▪ The acceptable print tolerances

The chances for a simple, reliable read, as well as a first read rate, increase with a higher print quality. The risk of substitution errors with a different bar-space sequence decreases as well.  The quality of printed barcodes through an offset or a matrix printer is typically much poorer than by using photographic methods. Barcode Verifiers are available which can measure and record the readability of the code to international standards.

Claricom is a supplier of Package Coding Management Systems and supply a range of ISO/CEN PC-Based barcode verifiers. (For more information visit www.claricom.com and select Quality Control))

Glossary - Print Quality

Barcode Contrast

Red-Light Barcode Readers
The large majority of barcode are pens and laser scanners with a laser tube (approx. 630nm) or the more common scanners using laser diodes (650nm to 670nm).  All of these are red light.

The best contrast, however, is achieved by means of black bars on a white background.

What may appear to the human eye as a good contrast, may not be the case to a red-light scanner.  Red bars appear the same as a white background to a red-light barcode scanner.  These images illustrate some of the colour combinations which do, and do not work, for a red-light barcode scanner.

Infrared readers

Pens, distance readers, hand-held readers with infrared illumination (900nm).   In this instance the print colour of the bar must be opaque on a white background.

Blue-Light Barcode Readers

Barcodes printed in red on a clear background (except for a red one) can be read by means of a CCD barcode reader using blue light such as a fluorescent lamp.

 

Example Auto iD Codes

Check-Digits – a “self-checking” capability

A key factor in barcode printing is the width of bars and spaces. The ratio of narrow to wide bars (or narrow to wide spaces) usually ranges from 3:1 to 2:1 depending upon print method and symbology, which gives a considerable degree of accuracy in decoding or “reading” data.

Most barcodes also have a “check-digit”, which is a further self-check.   The check-digit should always be used.

The check-digit or “control character” is a digit added to the code just before the stop character and is read as part of the barcode. For the barcode to be decoded successfully the check-digit included in the code does must correspond to the one calculated by the decoder using a symbology specific check-digit calculation.

 

Choosing a Reading Device

When choosing the most suitable reading device speed, size and construction (e.g. IP rating) are important, but optical resolution is essential.

Optical resolution closely depends upon the X-Dimension of the barcode (i.e. the width of the narrowest element)

 

Claricom can supply a wide-range of hand-held or unattended fixed-position barcode scanners, including equipment from Accu-Sort, Datalogic, HHP and Erwin SICK.

Claricom is a supplier of Package Coding Management Systems and can therefore advise on selection, installation and configuration of scanning equipment appropriate to your application. (For more information visit www.claricom.com and select Pack Validation)

Choosing a Barcode Symbology

The barcode symbology should be chosen to provide a reliable and accurate solution for the specific application and therefore provide the greatest possible reliability for the system in question.

It is advisable to use simple bar codes, especially for stock management and material handling applications (2/5 family, Code 39, bar codes with only 2 different space and bar widths) and an appropriate printing method adopted for the chosen symbology and vice versa.

Where the digits to be encoded range from 4 to 10, it may be advisable to use a short code, such as Code 39.

If the number of digits within the barcode ranges from 8 to 20, on the other hand, a code such as Interleaved 2 of 5 (ITF) should be used.

It is important to check the standards in place for the application and the bar width should be adapted to the resolution of the reading device (e.g. environment, reading distance etc).

Barcode Density:

Density of barcodes is most commonly measured in characters per inch (CPI).  Where the barcode reading is performed from a distance, it is advisable to use a barcode with a lower density.   It should be possible to select an appropriate barcode based upon barcode symbology and X-Dimension. Through variation of the X-Dimension of a barcode it is possible to vary the barcode density.

Common Symbologies:

Barcode	General	Advantages	Disadvantages
CODE 128 Linear Barcode	Code 128 is able to encode the complete set of ASCII characters without using combinations of characters (such as in Code 39), however, this is only possible by utilising 3 character subsets, A, B and C, which are used according to the problem to be solved. The different subsets can also be mixed. In order to encode the complete set of ASCII characters, the start characters A or B must be used in connection with the special characters of Code 128. Suitable for printing with: Offset, typographical, copperplate, laser printing, thermal transfer printing and phototypesetting	Can encode full ASCII character set. High information density.	Low print tolerance; the code uses four different bar or space widths. All ASCII characters cannot be represented with one character set<
EAN128 Linear Barcode	Logistics code used in trade applications EAN128 are different from Code 128 in that the start character consists of the combination of Start A, Start B or Start C with the character FNC1. (Further information below). Suitable for printing with: Offset, typographical, copperplate, laser printing, thermal transfer printing and phototypesetting	High information density.	Low print tolerance.
Datamatrix Code Matrix Code	Datamatrix has two main subsets, ECC000-140 & ECC 200.  ECC 200 is recommended. Data Matrix has the variable square size of a matrix. Symbols can range from a size of 10x10 to 144x144, thereby representing up to 16x48 symbol elements in a squared area. Datamatrix can encode 2,334 ASCII characters (7 bits) or 1,558 ASCII characters (8 bits). A horizontal and a perpendicular border form a corner, which is used to locate and orientate the symbol for reading. The information density amounts to 13 characters to 100 mm2. Suitable for printing with: all printing methods.	Very compact code. It is very reliable; powerful algorithm for error-correction (Reed Solomon). Even if up to 25% of the code is damaged a minimum amount of error-correction characters will still permit decode.	Reading requires image-processing devices that are typically more expensive and have a lower depth of field than linear barcode scanners.
PDF 417 ”Stacked” Code	PDF 417 is a version of “stacked” code based on its own structure. Characters are encoded in so-called "code words" which are assembled (“stacked”) to form a high-density barcode. At least two code words are used as check characters and error correction can be carried out by means of further code words.	Very compact code. Flexibility in adapting information to a given area thanks to variable width, height and information density.	The stacked structure must be respected during the reading.

EAN 128 Barcodes – Further Information

A subset of Code 128, EAN 128 is characterised by the use of a special character, The use of this combination of characters is reserved to the International Article Numbering Organisations, EAN and to the American Uniform Code Council, UCC. All application identifiers and their data contents can be represented with the UCC/EAN 128 bar code.

Three parameters have to be taken into consideration when defining the maximum length of an EAN 128 symbol:
  i. The number of encoded characters; this must not exceed 48 (excluding function characters)
  ii., The physical length of the code; this must not exceed 165mm (including Light Margins)
  iii. The number of data/symbol characters encoded excluding auxiliary and symbol characters; this must not exceed 35

Application Identifiers

EAN128 barcodes use “Application identifiers” to identify variable or fixed-length data strings within a barcode.   In order to transmit the length of predefined fixed-length strings after the reading has taken place, a table of indicators has been established.

Example: Durability Date

In the retail supply chain all products with a life of less than 42 days should have the life (durability date) encoded within the traded-unit EAN128 barcode.

The appropriate Application Identifiers (AI) are required as below. (*YY is the year.  MM is the month.  DD is the day).

Best Before / Best Before End	AI (15)	YYMMDD*
Use-By Date	AI (17)	YYMMDD*

Example EAN-128 Barcode
(01) Article Number
(15) Durability Date (example Best Before Date of 11^th February 1998)

Use of bearer bars is optional, but will help ensure accurate production of the EAN128-barcode symbol.

Claricom CLARiSOFT Package Coding Design Software includes an EAN128 wizard to help users automatically construct an EAN128 barcode to include the correct barcodes.  CLARiSOFT is one module of the Claricom suite of Package Coding Management software. (For more information visit www.claricom.co.uk/products/clarisoft)

 

© Claricom Limited, Nottingham, England 2004.  All rights reserved.