Common RFID FAQ
  • What’s the difference between passive and active tags?
    Active RFID tags have a battery, which is used to run the microchip's circuitry and to broadcast a signal to a reader (the way a cell phone transmits signals to a base station). Passive tags have no battery. Instead, they draw power from the reader, which sends out electromagnetic waves that induce a current in the tag's antenna. Semi-passive tags use a battery to run the chip's circuitry, but communicate by drawing power from the reader. Active and semi-passive tags are useful for tracking high-value goods that need to be scanned over long ranges, such as railway cars on a track, but they cost a dollar or more, making them too expensive to put on low-cost items. Companies are focusing on passive UHF tags, which cost under a 50 cents today in volumes of 1 million tags or more. Their read range isn't as far -- typcially less than 20 feet vs. 100 feet or more for active tags -- but they are far less expensive than active tags and can be disposed of with the product packaging.
  • How much information can the tag store?
    It depends on the vendor and the application, but typically a tag would carry no more than 2KB of data—enough to store some basic information about the item it is on. Companies are now looking at using a simple "license plate" tag that contains only a 96-bit serial number. The simple tags are cheaper to manufacture and are more useful for applications where the tag will be disposed of with the product packaging.
  • What’s the difference between read-only and read-write tags?
    Microchips in RFID tags can be read-write or read-only. With read-write chips, you can add information to the tag or write over existing information when the tag is within range of a reader, or interrogator. Read-write tags usually have a serial number that can't be written over. Additional blocks of data can be used to store additional information about the items the tag is attached to. Some read-only microchips have information stored on them during the manufacturing process. The information on such chips can never been changed. Other tags can have a serial number written to it once and then that information can't be overwritten later.
  • What is reader collision?
    One problem encountered with RFID is the signal from one reader can interfere with the signal from another where coverage overlaps. This is called reader collision. One way to avoid the problem is to use a technique called time division multiple access, or TDMA. In simple terms, the readers are instructed to read at different times, rather than both trying to read at the same time. This ensures that they don't interfere with each other. But it means any RFID tag in an area where two readers overlap will be read twice. So the system has to be set up so that if one reader reads a tag another reader does not read it again.
  • What is tag collision?
    Another problem readers have is reading a lot of chips in the same field. Tag collision occurs when more than one chip reflects back a signal at the same time, confusing the reader. Different vendors have developed different systems for having the tags respond to the reader one at a time. Since they can be read in milliseconds, it appears that all the tags are being read simultaneously.
  • What is the read range for a typical RFID tag?
    The read range of passive tags (tags without batteries) depends on many factors: the frequency of operation, the power of the reader, interference from metal objects or other RF devices. In general, low-frequency tags are read from a foot or less. High frequency tags are read from about three feet and UHF tags are read from 10 to 20 feet. Where longer ranges are needed, such as for tracking railway cars, active tags use batteries to boost read ranges to 300 feet or more.
  • Are there any standards for RFID?
    Yes. International standards have been adopted for some very specific applications, such as tracking animals. Many other standards initiatives are under way. The International Organization for Standardization (ISO) is working on standards for tracking goods in the supply chain using high-frequency tags (ISO 18000-3) and ultra-high frequency tags (ISO 18000-6). EPCglobal, a joint venture set up to commercialize Electronic Product Code technologies, has its own standards process, which was used to create bar code standards. EPCglobal intends to submit EPC protocols to ISO so that they can become international standards.
  • What are some of the most common applications for RFID?
    Tracking objects in the supply chain is one of the most common applications of RFID. Objects that are typically tracked include: consumer goods, reusable assets, high value tools, and manufacturing parts. RFID is also commonly used for access control, inventory management, payment systems, parking systems, and for tracking people, including workers, visitors, and patients.
  • What is EPC standard?
    The Electronic Product Code (EPC) is a standard specification to ensure unique serial numbers for each individual object hence it can be tracked independently. The standard allows different companies to share and exchange information in different data storage types efficiently through the same interface, thereby reducing time spent on integration.
  • What is EPC Gen 2?
    The Electronic Product Code is a global standard created by EPCglobal for use in many industries such as the RFID field. In 2006, the EPC Gen 2 was adopted by the International Standards Organization (ISO) as the ISO 18000-6C standard. ISO mainly focused on standards that deal with air-interface protocol and applications for RFID. EPC deals with more than just how tags and readers communicate; it also creates network standards to govern how EPC data is shared among different companies and organizations.
  • What are the advantages of RFID?
    RFID application enables inventory efficiency as line-of-sight is not required to read RFID tags. Although the initial cost may be high at first, the total cost of ownership can go down over the years and provide a good return of investment. On the other hand, an RFID tag is less vulnerable to damage comparing to barcode as it is protected by an outer case.
  • How does RFID work around water or metal?
    At ultra-high frequencies, it is difficult to track metal products or products with high water content since the radio waves reflect off of metal and are absorbed by water. In order to overcome this problem, RFID systems in these environments can use low frequency tags or high-frequency RFID tags, which work better in those environments.
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