Bar codes

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Written by: admin day of4/20/2011In the category Sledování výroby "
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Barcodes consist of dark lines and bright spaces printed vertically horizontally next to each other and are read by barcode reader. The lines and spaces are defined by a width and carrier of information. Barcode scanners emit in most of the cases the red light that is absorbed by dark lines and bright spaces reflected. The reflected light is then transformed into a sequence of electrical pulses of varying width and then compared with the corresponding combinations table . If it is found when comparing the corresponding sequence is indicated for the corresponding character string . Groups of lines at the beginning and end of the barcode play a special role - is used to synchronize the reader that supposedly generates a signal start / stop. Based on the technical specifications for the proper operation recommended reading light protective zone without printing from and against synchronization lines. Data that can be recorded and then subsequently read from the barcode can contain almost anything: employee number , product number , the number of manufacturing operations, the person's name , etc.




Features Barcode




   One of the main advantages of bar codes is accuracy. If we enter data manually error occurs every TRIS task , using barcode error will be recorded sometime around one million data capture . Moreover, these errors can be almost eliminated on the basis of the check digit , which is calculated from the previous digits code.
   Speed ​​is another equally important advantage that plays when deciding how to record and manage items produced a major role . Bar code scanners are at least three times faster than manual data entry.
   Barcodes can be printed on any material resistant to moisture , acids, weather fluctuations , etc., and we can customize the size of the product . Flexibility is therefore another important feature . With all these attributes, we can expect higher productivity and efficiency of operations .


Basic elements barcode


X - Width - This is the smallest possible line width or spacing
R - bright band - its width is less than 2.5 mm , but it is advisable to ten times the width of the module
H - height of the code - it is the vertical dimension of the strip code , the recommended length is 10 % of the belt for manual reading , 20 % of the strip read with a scanner , minimum is set at 20 mm and the exception is the EAN bar code , which has a suggested 75 % length of the belt .
L - length of the code - this is the length of the strip from the first signs start to the last stop sign , does not add to the bright band
C - contrast - is determined as the difference between the brightness of the reflection and background brightness of the reflection lines divided by the brightness of the reflection background. For readable code should be greater than 0.7 .
The types most commonly used barcodes




    Barcode in which we can encode a large number of data types. In závyslosti on the type codes can be found in which it is possible to encode only numbers . So just encode characters such as 1, 8, 9, etc. or enabling codes to encode just the basic alphabet. But there are also types that encode both numbers and alphabetic characters , these are called alphanumeric . We also found types of bar codes that can encode a set of 127 or 255 characters of ASCII table. Generally, then barcode types differ in length and structure of the code , the coding method , and finally a typical field of application . If we barcodes compared in terms of length, we would find that some have a variable length and characters are stacked behind or under each other like words in a sentence. Others have a fixed length , such as EAN 8 to EAN 8 digits or 13 digits with 13 . The number and types of codes that are currently used in tens, therefore only a fraction of the total and that even taking into account the possible use in the industry.


EAN 13 and EAN 8


    These codes are the most widely used in commercial networks where referred to as a catalog . Encoded can be 0-9 digits and each digit is represented by two lines and two spaces . As already mentioned, contain 8 digits for EAN 8 and EAN 13 to 13 ( Fig. 1 ) . Each country involved in international association of European Article Numbering ( EAN ) can use this barcode . The first 2-3 digits of the code identifies the state , the Czech Republic has a number of 859 Next 4-6 digits determines the supplier or manufacturer, are reserved for other goods. The last digit is a control function , allows you to verify the accuracy of decoding.


 
FIG. 1: Barcode EAN 13


UCC / EAN 128 , Code 128


    Family of these codes enables you to encode more information than is the case EAN 8 and 13 are alphanumeric codes of variable length . The code can read the packing date , date of manufacture , maximum or minimum durability , length, width, weight , volume, area , article number , etc. These codes are used in industry and are called jimy business or logistics units .
   Using codes UCC / EAN 128 can encode up to 96 characters of ASCII table and 11 functional attributes. Each data encoded in the code has its own application identifier (AI ) , which accurately determines the type of data . Each character is made ​​up of lines or spaces with a total width of 11 modules. UCC / EAN 128 is special standardized version of Code 128
   Do Code 128 (Fig. 2 ) , it is possible to encode all printable ASCII characters ie 128 characters. Always three bars and three spaces depict one character and the total character width is again 11 modules . Line width or spacing can be 1 , 2, 3 or 4 modules .
 
FIG. 2: Barcode Code 128
Code 39


    This code is an alphanumeric code ( Fig. 3 ) is able to encode letters A through Z, digits 0 to 9 and seven special characters. Each character is made ​​up of five lines and four spaces , composed of 3 wide and 6 thin lines or spaces. Characters start and stop us represents the character " Stars " . CODE 39 is not supported by small letters, they are automatically converted to input to uppercase. The code was designed in 1974 for industry and trade. Thanks to its reliability , the error occurs after reading about 30 million characters spread to the automotive , armaments and other industries , is also used for example in health care.


FIG. 3 : Barcode Code 39


Code 2 of 5


    Barcode Industrial 2/5 has been designed for internal industrial applications in 1968 by Identicon Corporation. This code allows for a relatively high density writing , it may be up to 8 characters per 1 cm and its length may vary depending on the density of the registration number or characters . It encodes only numeric digits 0-9 and is made up of character start and stop . Each character of the code is illustrated by five lines, three are narrow and two wide. It is interesting that the bright bands do not carry information. The width of the light strip is recommended to set equal width module X. width wide and narrow element corresponds to a ratio of 3:1. Example coded in Tab. 1, where 0 represents a narrow and one wide element. These codes are suitable for low-quality printing , the substrate hardship reading or receiving the wrong color due to the wide range tolerančnímu .


 
Tab. 1 : Coding table


Source: KODYS , spol . s r.o. . barcode
          http://cs.wikipedia.org
          Cosmotron Bohemia s.r.o. . Barcodes
          Smejkal, Ladislav . Barcode scanners - an overview of the market. • Automation vintage 50 • Number 11 • November 2007
          ELOS Trade , p r o . Barcode
          Ondřej Škrabal : Evidence and analysis of the length of duration of work tasks for mold

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