What Is the Important Comparison Between RFID and Bar Codes?

Can you please explain the differences?

—Name withheld

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There are two big differences between bar codes and RFID. The first is that bar codes require line of sight, while RFID does not. That is, with a bar code, there must be no obstruction between the scanner and the bar code for it to be read. Radio waves penetrate materials, so you could read RFID tags on 100 items inside a box without opening it. This is a critical difference in many applications. For example, if you have boxes in random orientation on a conveyor, it is very difficult to read a bar code consistently. With an RFID transponder, it's relatively easy.

This difference is what makes RFID the only truly automatic data-capture system. You don't need a person to pick up a scanner and orient the bar code to the scanner. It is also the reason why RFID can be cheaper than bar codes. When people talk about cost, they rarely include the cost of the labor required to point the scanner and pull the trigger.

The second big difference is the amount of data that each can carry. A conventional bar code does not store a serial number, so every bar code on a can of Coke, for instance, is the same. 2D bar codes can store more data, including a unique serial number, a URL or some other information. But that's it. Once you've created the bar code with a serial number or URL, you can't add more data. With a passive ultrahigh-frequency (UHF) EPC transponder, you can write a unique 96- or 128-bit serial number to the transponder and then add additional information in user memory blocks. For example, you could write the ID of the store to which an item should be shipped. High-memory RFID transponders allow you to store entire parts histories and other relevant information.

A third—but, to my mind, less important—distinction is the ability to write to the RFID tag. Once a bar code is created, you can't add additional information. With RFID, you could write and rewrite information to user memory. This can be useful for, say, updating information on the status of a tagged item (if an item was returned by a customer, or if a part was defective and should not be used).

There are other differences, but these are the key ones. And this is not to say that bar codes are always inferior to RFID. In applications for which you have line of sight and can orient the bar code to the reader, a bar code might work just fine. As always, you need to choose the proper technology for your particular applications.

—Mark Roberti, Founder and Editor, RFID Journal