Guide to reading the report

This guide explains the terms used in reports from GS1 BarcodeCheck. The report is based on a template developed in a global collaboration of trading and logistics companies together with barcode equipment suppliers.

Barcodes are verified against GS1 General Specifications. GS1s standards include relevant parts of ISO/IEC 15416 Bar Code Print Quality Test Specifications for Linear Symbols.

Tests made using the ISO standard compare a barcode with a "perfect" symbol. When a barcode is tested using the GS1 standard, a check is also made of the barcode's readability under the conditions where it is intended to be used. If a barcode is approved under the GS1 standard, it is also approved under the ISO standard.

An exemple of a report from GS1 BarcodeCheck.

1. Picture of verified barcode

The picture shows which barcode has been verified and the area included in the verification.

2. Issue date

The date and time the report was created.

3. Type of barcode

The type of barcode that has been verified.

Note that barcode type EAN/JAN-13 is the same as barcode type EAN-13 since "JAN-13" is the Japanese equivalent of EAN-13.

4. Data encoded

The information that has been read from the barcode.

5. GS1 General Specifications for Linear Symbols tested environments

Here is a summary of the result from the tests accordning to GS1s standard. The barcode is verified as readable in the environment in which it is intended to be used. The are three different environments:

1) Omni-directional retail point of sale (POS)

Here the readability of the barcode on a consumer unit at point of sale is tested.

Barcodes tested in this environment: EAN-13 och EAN-8.

2) General Distribution (pallets, outer cases)

Here the readability of pallet labels and barcodes on outer packages is tested in an environment where scanning is automatic, for example in an automated warehouse.

Barcodes tested in this environment: EAN-13, ITF-14 and GS1-128.

3) GS1 Pallet Label

Here the format of the pallet label is tested, that the barcodes conform to the standard and that the human readbale information is the same as in the barcode.

A pallet label can have more than one barcode printed. The SSCC is in the lowest barcode on the label. Other information is printed above this. The result of verification is reported per barcode.

Result

The result can be:

  • Pass – The barcode is approved for use in this environment.
  • Fail – The barcode is not approved for use in this environment.
  • N/A – The barcode has not been tested for use in this environment.

6. Overall ISO Symbol Grade

Here is a summary of the test against the ISO standard. The barcode is compared with a "perfect" symbol. The result is reported as "g.g/aa/www (G)" where

  • g.g – Measured value of barcode quality according to ISO. A number with one decimal place. The maximum value is 4.0.
  • aa – The reader aperture in mils (in/1000).
  • www – The wavelength of the light source in nm
  • G – Measured value of the barcode quality according to ANSI.

7. Comments

Here is reported if the barcode is approved or not. If it is not approved the reason is given and suggestions for correction made. Note that if the barcode has failed on several points, it is not always possible to give a complete suggestion for a solution.

8. Reading the table

The table shows the results of the checks that have been made against the GS1 standard. For each check, the following are reported:

  • Assessed. Here any measured values are reported.
  • Within Standard Range. Here is an indication of whether the barcode has passed (OK) or failed (NOK) each test. If this parameter has not been tested, this shows N/A.
  • Required. Here the requirements which must be met for the barcode to pass are given.

9. Symbol Structure

A check is made that the symbol is correctly structured. If the barcode is unreadable then this parameter cannot be checked. An incorrect check digit is an example of a structure error.

10. X-dimension

The X-dimension is the width of the narrowest bar. The limits depend on the enviroment the barcode is to be read in and the barcode type.

You can find limits for the X-dimension in the Barcode size guide

11. Bar Code Height

The limits for barcode height depend on the barcode type and are measured differently for different types:

  • EAN-13, UPC-A, UPC-E and EAN-8 – the height is measured from the lower edge of the human readable text to the top of the bars.
  • ITF-14 – the height is measured from the bottom to the top of the bars, excluding the bearer bars.
  • GS1-128 – the height is measured from the bottom to the top of the bars.

You can find limits for the barcode height in the Barcode size guide

12. Quiet Zone (Left), (Right)

There must always be a quiet zone on the left and right of the symbol. The quiet zone is a blank area which ensures that adjacent information such as the package artwork does not confuse the reader. The limits for the quiet zone depend of the barcode type.

You can find limits for the quiet zones in the Barcode size guide

13. Human Readable

The characters under the barcode are compared with the data read and must agree.

14. Bar Code Width

For GS1-128 a specific check is made that the barcode width does not exceed the maximum permitted.

15. Validity of GS1 Company Prefix

A check is made that the data in the barcode has a valid GS1 Company Prefix.

16. Data Structure

Here errors caused by incorrect use of application identifiers in the barcode are reported. Application identifiers (AI) are used to encode data additional to the GS1 identifier in a GS1-128 barcode.

Common errors

  • FNC 1 (function code 1) used incorrectly. FNC 1 is the first character in a GS1-128 symbol which indicates that the information is encoded according to GS1 standards.
  • Wrong number of digits in GTIN. When a GTIN (Global Trade Item Number) is encoded in GS1-128, it must always be 14 digits. If only 13 digits of the GTIN are encoded the remaining information will be misaligned and interpreted incorrectly.
  • Incorrect use of variable length field. When a GS1-128 symbol encodes data of variable length (e.g. batch number or serial number) this field should be placed last in the barcode. If a variable length field is placed between two other fields, then it must be terminated with a separator (FNC1).
  • Parentheses around the AI in the barcode. An application identifier (AI) is a code which indicates what information is in the following field. AIs are printed in parentheses in the human readable text, but these are not encoded in the symbol.
  • Wrong use of AI. An application identifier (AI) is a code which indicates what information is in the following field. e.g. AI (02) is the GTIN for a contained item. AI (02) must always be used together with AI (37) which is the number of contained items.

17. Reading the table

The table shows the results of the checks that have been made against ISO/IEC 15416. For each check, the following are reported:

  • Assessed barcode ISO/ANSI grade. Here measured values are reported for the barcode quality according to ISO/ANSI.
  • Within Standard Range. Here is an indication of whether the barcode has passed (OK) or failed (NOK) each test.
  • Required. Here the requirements which must be met for the barcode to pass are given.

18. Overall ISO Symbol Grade

Here is a summary of the test against the ISO standard. The barcode is compared with a "perfect" symbol. The result is reported as "g.g/aa/www (G)" where

  • g.g – Measured value of barcode quality according to ISO. A number with one decimal place. The maximum value is 4.0.
  • aa – The reader aperture in mils (in/1000).
  • www – The wavelength of the light source in nm
  • G – Measured value of the barcode quality according to ANSI.

19. Decode

This checks that the barcode has been constructed correctly, i.e. that the bar/space combinations give the correct digits, that the check digit is correct and that the quiet zones are large enough.

Common errors Proposed actions
Information in the symbol is incorrectly coded. Correct the symbol to conform to GS1 standards.
The quiet zones are too small and might interfere with correct reading. Correct the quiet zones to conform to GS1 standards.
The check digit has been incorrectly calculated. Recalculate the check digit.
The bar code has too many defects.

Correct the cause of the defects by adjusting print pressure (offset printing).

Change or clean the print head (thermo or ink-jet printing) to minimise for example speckling.

20. Symbol Contrast

In order for a barcode to be readable there must be a distinct contrast between the light and dark parts. Symbol contrast measures this difference.

Common errors Proposed action
Background is too dark and reflect light poorly compared with the bars

Use a lighter material or a material that is more matt and reflects light better.

Change the background colour to one that reflects light better.

Remember to check that any actions do not increase the bar width.

The bars are too light and reflect too much light compared with the background.

Choose a darker colour for the bars so that they reflect less light.

Increase the quantity of ink.

Raise the temperature of the print head (thermo printing).

Remember to check that any actions do not increase the bar width.

21. Minimum Reflectance

In order for a barcode to be readable there must be a difference in reflectance between the light and dark parts. All dark bars have low reflectance and the light spaces high reflectance. The area with minimum reflectance is the symbol's darkest part.

Common errors Proposed action
The bar colour is too light or contains too much red, which means the bars reflect too much light compared with the backgrouond.

Change the colour of the bars to one with lower reflectance.

Increase the quantity of ink.

Raise the temperature of the print head (thermo printing).

Remember to check that any actions do not increase the bar width.

22. Edge Contrast

In order for a barcode to be readable there must be a distinct contrast between a bar and the adjacent light area. Edge contrast measures the lowest such contrast.

Common errors Proposed action
There are colour shifts in the label material which means that the background reflectance varies, for example when using recycled material that contains dark spots. Use a more homogenous material or one that reflects light better.
The quantity of ink in the bars varies which changes their reflectance. Adjust the printing parameters so that pressure is more even across the symbol.

23. Modulation

Modulation is the relation between edge contrast and symbol contrast and measures how well a scanner can detect the difference between wide and narrow elements (bars and spaces).

Common errors Proposed action
There are colour shifts in the label material which means that the background reflectance varies, for eample when using recycled material that contains dark spots. Use a more homogenous material or one that reflects light better.
The quantity of ink in the bars varies which changes their reflectance. Adjust the printing parameters so that pressure is more even across the symbol.

24. Defects

Defects can be dark spots in the light spaces or light spots in the dark bars. They occur, for example, during printing. Defects create "noise" when the symbol reflectance is measured and can result in the barcode being unreadable.

Common errors Proposed action
The quiet zones are too small and might interfere with correct reading. Correct the quiet zones to conform to GS1 standards.
The bars are split by white vertical lines caused by a dirty or damaged print head.

Contact you printer supplier for suggestions on how to correct this.

The error can be caught during printing by printing a horizontal line along the top edge of the symbol. This makes it easier to spot any white vertical lines.

Reading is disturbed by dirt, spots, etc. on the label. Clean the printer and print head regularly.
Poor print quality

Contact you printer supplier for suggestions on how to correct this.

Add ink.

Change label material

25. Decodability

Decodability is a measure of how easy it is to differentiate between different widths of bars and spaces. Printing errors and defects can cause a narrow bar to be confused with a wide one. Each type of barcode has limits for when two bars of different widths can be confused.

Common errors Propoased action
Wrong bar width

Rotate the symbol 90 degrees so that the bars run in the direction of printing

Raise the temperature of the print head (thermo printing).

Contact you printer supplier for suggestions on how to correct this.
Bar widths vary

Check the bar widths in the print master since the error can have occurred there.

Contact you printer supplier for suggestions on how to correct this.