What is an RFID System and how does it work?
Basically, RFID systems have at least two components: readers and tags.
- A reader (or “interrogator”) is a device that has one or more antennas that send electromagnetic waves to RFID tags and receive signals back from the tags. Readers may be handheld, fixed, or vehicle mounted.
- A tag (or “transponder”) is usually a microchip attached to an antenna, both of which are contained within a package (a plastic case, for example) or substrate (such as a label).
- Some RFID tags are “passive” – lacking power sources of their own, passive RFID tags absorb the electromagnetic waves from readers and use them to power their microchips’ circuits, which in turn trigger response signals that broadcast their identification numbers back to the readers.
- Other RFID tags are “active” – powered by batteries or other energy sources, active RFID tags transmit signals containing their identification data at set intervals (every three seconds, every four minutes, whatever – you set the interval to meet your need). Readers pick up these signals and use them to determine the tags’ locations. Active tags also contain on-board electronics – a possible combination of sensors, microprocessors and input/output ports – that enable the tags to be used in more sophisticated applications, where things like an item’s temperature or other handling conditions are critical.
Beyond readers and tags, RFID systems may be integrated with software that can log and interpret tag reads and incorporate the data into your business applications.
What are low-frequency, high-frequency and ultra-high-frequency RFID systems, and which one do I need?
Frequency refers to the rate at which radio waves travel between readers and RFID tags to communicate with each other. Because these waves act differently at different frequencies, some options are better suited than others for particular environments and/or types of object being tagged.
- Broadly speaking, low-frequency RFID systems (which operate at about 125KHz) have a relatively short communication range (from a couple of inches to about 1.5 feet), require little power, and work well on non-metal items, particularly items with high water content. Some low-frequency RFID applications include vehicle immobilization, product authentication from manufacturer to retailer, access control and animal tracking.
- High frequency RFID systems (13.56MHz) have a better read range (up to 3 feet) and can work well with metal items. Some high-frequency RFID applications include library book tracking, airline baggage tracking, healthcare patient tracking, and maintenance data logging for sensitive equipment that requires regular status checks.
- Ultra-high-frequency RFID systems (860–960MHz) have a significantly longer read rate (up to 50 feet under some conditions) and faster data transfer speed, but require more power. Often used in distribution and logistics applications, UHF RFID is also used in electronic highway toll collection systems, manufacturing work-in-process and more.
Because there are so many variables to consider and so many options available, an experienced RFID integrator like Strategic Systems & Technology can be an invaluable resource. We’re here to help.
What’s the read range in a typical RFID system?
The distance across which an RFID reader and tag can communicate with each other is usually referred to as a read range. Read ranges depend on a number of factors, including:
- the frequency over which the RFID system runs (the lower the frequency, the closer the components have to be – i.e., low-frequency systems tend to have a read range of less than 1.5 feet, high-frequency systems around 3 feet, ultra-high systems up to 50 feet);
- the shape of the reader antenna; according to tag manufacturer Omni-ID …
- a circular antenna reads from a much wider angle and shorter distance than a linear antenna, and it can read tags in different orientations, but
- a linear antenna can have better read performance and accuracy when the tag orientation is controllable;
- the shape of the reader antenna; according to tag manufacturer Omni-ID …
- the size of the tag antenna (a larger antenna can absorb and return more energy from a greater distance; incidentally, antenna size tends to influence overall tag size – the larger the antenna, the larger the overall tag size);
- and the power output of both the reader (more power enables reads from greater distances) and the tag (if it’s an active tag with a healthy battery, the range is longer – up to 300 feet in some instances; passive tags are dependent on the energy output of the reader to enable the echo-back of its signal, but somewhere between 20 and 50 feet for UHF systems).
Furthermore, environmental conditions also can affect read range: liquids can absorb RF energy, metals can shield or reflect RF energy, competing radio waves from different devices can interfere with each other, the proximity density of the tagged items may mandate using an RFID system with a shorter read range, and so on. But don’t worry. Remember, we’re here to help.
What kinds of – and how much – information can be stored on an RFID tag?
Passive RFID tags generally carry between 64 bits and 1 kilobyte of memory, while active tags can hold much more. The majority of tags in use today carry less than 256 bits of memory, with 96 bits being the most common. Data encoded on RFID tags ranges from simple serial numbers to the same types of information found in barcodes; however it also is possible to include such details as product size, color, date of manufacture – even a history of the product’s touch-points along its path to the distribution center or showroom floor.
Often, the context for the read – the location, time and/or setting where a tag is read – provides the business-critical intelligence that makes RFID such a valuable technology. For more than a decade, Strategic Systems & Technology has been designing custom software applications that understand this information in relation to our customers’ business requirements, providing the tracking and reporting they need.
Are RFID tags reusable?
With respect to lifecycle, passive RFID tags can be used practically indefinitely; active RFID tags, due to the power source requirement, may need new batteries or may need to be replaced entirely every two to three years. Whether or not tags can be used to track more than one item over their lifetime or for maintaining different types of information for a particular item over its lifecycle depends on whether the microchips inside the tags are read-only, WORM (write-once, read-many), or read-write.
- Information contained on read-only tags is determined at the point of manufacture and cannot be changed.
- WORM tags may carry a serial number from the manufacturer and can be encoded with additional information just once, but cannot be overwritten afterward.
- Read-write tags generally contain an unchangeable serial number but also a number of protectable data fields that can be overwritten as often as needed.
How much do RFID tags cost?
The price of RFID tags, like any highly configurable technology, depends on many factors: whether the tag is active or passive, the memory capacity of the microchip, the material encasing the tag, the durability of the tag, the adhesive type, order volume, and much more. Because of these considerations, tag vendors typically do not give out blanket quotes.
RFID Journal addresses the question this way:
Generally speaking, active tags are $25 and up. Active tags with special protective housing, extra-long battery life or sensors can run $100 or more. A passive 96-bit EPC inlay (chip and antenna mounted on a substrate) costs from 7 to 15 U.S. cents. If the tag is embedded in a thermal transfer label on which companies can print a bar code, the price rises to 15 cents and up. Low- and high-frequency tags tend to cost a little more.
In general, the more widespread adoption of UHF RFID systems has brought the cost of UHF tags down most dramatically, making them some of the most affordable RFID tags on the market.
We at Strategic Systems & Technology do not manufacture RFID tags, but we do partner closely with the industry’s leading tag and inlay manufacturers – including Omni-ID, Avery Dennison and Alien Technologies – to source the most appropriate components for our customers’ complete RFID solutions. Click on Contact Us or Ask a Question, or call us at 678-389-7200 to discuss your RFID needs with us.