Radio frequency identification (RFID) is a high-tech method of automatic identification that is familiar to pet owners who microchip pets for permanent identification. The technology has many uses in science, livestock management and commerce. An RFID system consists of a tag; an antenna or reader; a controller; and a database to store information about tagged objects. Tags can be attached in various ways and used to track and identify anything from airport baggage to wildlife.
How it Works
RFID antennae or readers, which can be portable or mounted on a floor, on conveyor belts, or elsewhere, receive radio frequency transmissions from tagged objects and pass the data on to a controller. Unlike a bar code reader, some RFID readers do not require a clear line of sight to a tagged object. The controller manages the transfer of data to the host system, which usually is a computer. Controllers are available that can communicate with most networks. Some RFID readers can be programmed.
Passive Tags
RFID tags may be passive, semi-passive, or active, depending on whether they originate communication and how that communication takes place. Passive tags have no battery. They have indefinite life expectancy, but environmental factors such as wind, water and metal can limit the range at which they can be read to 10 feet or less. Communication is initiated by a reader, which transmits radio signals to the tag, where they couple with the antenna on the tag to create a magnetic field. The tag authenticates the incoming signal and responds to the reader. Passive tags are typically used in building access systems and for tracking consumer products through the supply chain.
Semi-passive Tags
Like passive tags, semi-passive tags do not originate communication. They do have batteries, however. The battery provides power for the transponder circuitry, enabling information such as ambient temperature to be stored on the tiny silicon microchip. Semi-passive tags can be combined with sensors to provide a means for monitoring environmental factors such as energy consumption or weather conditions.
Active Tags
Active RFID tags are powered by disposable or rechargeable batteries; the life of the battery dictates how long the tag can operate. An active tag transmits data when interrogated. Active tags are significantly more expensive than semi-passive or passive tags, but they can initiate communication and can communicate over distances of 100 feet or more. Active tags are designed to periodically broadcast data, such as global positioning system (GPS) coordinates, to RFID readers within range.
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