Categories of RFID:
RFID can be categorized with respect to;
- Read/Write Property
RFID tags are further broken down into two categories;
- Active RFID Tags
- Passive RFID Tags
Active RFID Tags:
They are battery powered. They broadcast a signal to the reader and can transmit over the greatest distances (100+ meters). Typically they can cost £5 - £20 or more and are used to track high value goods like vehicles and large containers of goods. Shipboard containers are a good example of an active RFID tag application.
Passive RFID Tags:
They do not contain a battery. Instead, they draw their power from the radio wave transmitted by the reader. The reader transmits a low power radio signal through its antenna to the tag, which in turn receives it through its own antenna to power the integrated circuit (chip). The tag will briefly converse with the reader for verification and the exchange of data. As a result, passive tags can transmit information over shorter distances (typically 3 meters or less) than active tags. They have a smaller memory capacity and are considerably lower in cost (less than £1) making them ideal for tracking lower cost items.
There are two basic types of chips available on RFID tags;
These chips are programmed with unique information stored on them during the manufacturing process – often referred to as a ‘number plate’ application. The information on read only chips can not be changed.
With these chips, the user can add information to the tag or write over existing information when the tag is within range of the reader. Read / Write chips are more expensive that Read Only chips. Applications for these may include field service maintenance or ‘item attendant data’ – where a maintenance record associated with a mechanical component is stored and updated on a tag attached to the component.
Another method used is something called a "WORM" chip (Write Once Read Many). It can be written once and then becomes "Read Only" afterwards.
RFID Vs Bar Code:
It is important to understand the significant differences between RFID and bar code to appreciate the benefits RFID can provide. Bar code and RFID are both identification technologies that hold data that is accessed by some type of reader. In actuality, they complement each other very well and can be used effectively side by side in many applications. Bar code is an optical technology, and RFID is a radio technology. The ways these technologies exchange data account for most of the differences between RFID and bar code and help determine where each identification technology is best put to use.
As a radio technology, RFID requires no line of sight between the reader and the tag to exchange data. RFID tags therefore can be read through packaging, including cardboard containers and plastic wrap used to seal pallets. RFID is subject to interference, however, particularly from metal, so potential sources of interference must be recognized and accounted for during system planning.
Because no line of sight is required, tagged objects can be read regardless of their orientation through the use of optimized RFID systems. Items don’t have to be placed label side up onto conveyers to be read, paving the way for unattended handling. If workers are required to place items on conveyers to be read, they will be more productive if they don’t have to locate and align labels when handling objects.
RFID readers can automatically recognize and differentiate all the RF tags/inlays in their reading field. This simultaneous processing capability provides additional flexibility for material handling, packaging, and sorting operations because there is no need to maintain spacing between objects to ensure they will be read. The ability to read dozens or even hundreds of tags per second makes RFID ideal for high speed sorting, receiving, cross docking, and other applications. The data capacity of RFID tags/inlays enables them to carry all the same information as bar codes and more. Just as bar codes differ in data capacity, RFID tags/inlays are available with various memory size and encoding options.