Ebook on Industrial Traceability: How Barcodes Work

Introduction

In recent years, traceability has become a major theme in global commerce. Industries using a large number of component parts that come from many different subcontractors are now beginning to benefit from their investments in traceability. These investments can facilitate better management of product recalls, providing considerable cost savings. They can also improve brand perception in the marketplace. Additionally, traceability gives clients a better understanding about the provenance of a product. It validates whether a product conforms to the needs and specifications of a client. As for the manufacturer, traceability enables better tracking of what is sent to clients and a better understanding of what is produced, assisting in continuous improvement efforts. The sources of real or potential problems can then become easier to identify. Typically, the characteristic traced takes the form of serial numbers, batch numbers, date codes, model numbers, etc., and is linked to a database. 

Alphanumeric serial numbers have been used for decades. They are simple and easily read by workers. Barcodes were created in the emerging information technology age of the 20th century. Barcodes provide unique identifiers for retail products. As they can be read automatically, they reduce checkout times and errors. Barcodes were first introduced in the late 1940s. With the introduction of barcode readers and UPC symbols in the 1970s, the now familiar one-dimensional barcodes became the norm. Since only limited information can be stored in these barcodes, databases are often used. They add context to the information extracted from simple barcodes. In the 1990s, the first two-dimensional codes were developed. 2D codes can be used to store even more information on a smaller surface, often even eliminating the need for separate databases.

This eBook was developed to help you make insightful choices regarding the type of traceability format you require. First, we will explain 1D barcode and 2D code functions, and how they differ. Then, we will discuss how the GS1 standard assures barcode 
quality. Finally, we will explore a comparison of both formats. After reading this document, you should be able to identify the best solution for your needs.

Barcode Structures and How They are Read

2D codes have many traceability advantages, but simple 1D barcodes are still used in many industries. Writing and reading 1D codes is easier than 2D codes as no image processing software is needed. Only a light source and a photodetector are required.

2.1 Common Barcode Types

Numerous structures and standards exist for barcodes. All are based on associating black and white lines with symbols. The symbols may be alphanumeric or simply numeric, depending on the standard.

2.1.1 Code UPC-A

UPC-A barcodes (Universal Product Codes) are very common, particularly in retail. However, the standard only references numbers, letters are not considered. This limits their usefulness for industrial traceability.

2.1.2 Codes 128 and 39

Code 128, named for its capacity to represent all characters of the ASCII 128 set (American Standard Code for Information Interchange) is often used internally in manufacturers’ supply chains to ensure product maintenance and handling

On the other hand, Code 39, a less compact equivalent of Code 128, is mainly used in the automotive and defence sectors.

2.2 Barcode Structure and Readability

Figure 1 shows a Code 128 barcode structure. It is divided into four sections and can host 108 symbols. Three of the symbols identify the beginning of the code and two indicate its end. Each section contains a certain number of symbols. A symbol is an alternating combination of three black lines and three blank spaces with varying widths. Each symbol is in turn associated with a specific alphanumeric character from the ASCII 128 character set. Here is a description of each barcode component:

Figure 1: Example of a 128 barcode and its different sections

1 – Quiet Zones
The beginning and end of the barcode are each surrounded by a quiet zone. These zones improve the code’s retrieval during reading. The quiet zone consists of a series of white lines.

2 – Start/Stop Characters
Every Code 128 barcode has the same three symbols at the beginning and same two symbols at the end. They identify the reading direction.

3 – Code Data
This section always occupies the largest space. It is 103 symbols long and carries the unique information about the marked product.

4 – Validation Character
After the code data, there is a verification symbol to verify if the code data has been read correctly. Each alphanumeric character of Code 128 is associated with a unique number. After decoding the code data, an algorithm takes the numbers paired with the characters and makes a calculation. The result is a new number that represents a unique alphanumeric character. The last symbol of the barcode, the validation character, should be the same as the one calculated by the barcode reader. Otherwise, the code has not been read properly and the barcode will need to be rescanned.

5 – Human-Readable Interpretation
This will be discussed in detail in section 5. Tracking Codes and Global Standards (GS1), for now, suffice to say that it is the message encoded in the barcode spelled out in plain English.

2.3. How Barcode Readers Work

Black lines reflect less incident light than white lines. The barcode reader takes advantage of this fact. A light source is directed within a particular field of view that includes the barcode and a photodetector measures the quantity of light that is reflected. Of course, the total energy measured differs depending upon whether the detector “sees” a black or a white line. The photodetector generates an electric current proportional to the light intensity sensed. The variations in the electric current are then analyzed and the alternating black and white lines are extracted. Finally, the electronic data generated is associated with a product, and, of course, to the product’s information in the database (price, model number, serial number, date, work order, batch number, for example).

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