Introduction to RFID
RFID technology is all around us, seemingly operating like a bit of magic. RFID transponders are in your car for E-ZPass and, you can frequently find RFID tags on clothing in retail stores. (Have you ever been embarrassed or annoyed at the alarm that went off as you were leaving the store?) The RFID market continues to grow and is expected to rise to over US$18 billion by 2026. In this article, we will look at a few common questions about RFID. Most of the questions here relate specifically to passive UHF RFID. Other forms of RFID, such as active RFID, are not addressed in this article.
What is RFID?
RFID stands for Radio Frequency IDentification. It is similar to barcodes in that the RFID EPC (Electronic Product Code) is a number that can be used to identify a specific item. It expands on barcodes by allowing user data to be stored in the RFID tag that provides additional information about an item. For example, the RFID tag could store the manufactured or expiration date. Sometimes, the EPC number is printed on the RFID tag with a matching barcode so the tag may be read with a barcode scanner, as well. Some newer RFID tags have sensors, such as temperature and humidity, that enhance RFID’s capabilities.
How does RFID work?
RFID readers generate radio waves at specific frequencies. These waves interact with the RFID antenna on a tag to create a tiny amount of energy. This energy powers the RFID chip to allow it to respond to the identification, read or write requests from the reader. The energy is also used in passive sensor tags to measure humidity or temperature and report it to the reader.
Is RFID expensive?
RFID tags do cost more than barcode labels, and the RFID reader, also called an interrogator, is more expensive than barcode readers. The cost has come down significantly in recent years. Readers typically cost several hundred dollars (often less than $1000), and tags can range from a few cents (high quantities of paper tags) to a few dollars (highly rugged tags) each. A discussion of goals, with subsequent time and material savings can help calculate a return on investment.
Is RFID appropriate for my use case?
Any company which needs to track people, things, or events can make use of RFID. Probably a better question is whether RFID is effective for your specific needs. As discussed above, it is important to consider your objectives in conjunction with expected savings to determine the return on investment. Additionally, environmental conditions can impact your decision on whether or not to use RFID. For example, placing RFID tags on metal surfaces increases the cost of the tags (special metal-mount tags are required), and metal creates reflection (bouncing of the RFID signals). You will need to consider these factors when using RFID in this environment. Metal-mount (aka “anti-metal” or “universal”) tags are effective and have been used in many environments, but one must consider the placement and expectation of those tags.
How far does RFID read?
The short answer is that RFID can read from a few inches to many feet (e.g. 100 feet in ideal conditions). The long answer is complex. A lot of factors determine how far (or near) RFID can read. As was mentioned above, the RFID radio waves “excite” the tag’s antenna, creating power. So it depends on the antenna design, antenna power, tag design and material, other surrounding material, other neighboring readers, and much more. It is important to note that the RFID power can be turned down to reduce the range that RFID is reading.
How many RFID tags can I read at once?
Again, the answer is complex. The short answer is that you can read a few to hundreds of tags per second. In optimal environments, a reader may be able to scan 1000 tags per second, while in more challenging environments only a handful of tags may be read per second. The process of inventorying tags is much more complex, and directly relates to the RAIN or Gen2 protocol specification for UHF RFID. To understand RFID settings and configuration, you will need to learn about RFID Sessions or consult an RFID expert.
How is RFID used for triggering events?
As part of the business logic of the application, events can be triggered programmatically when an RFID is in range of a reader or when it leaves the area. A technical person can program events for specific tags or range of tags or by the data that is present in a tag. For example, when a forklift moves a pallet into a truck, passing an RFID reader at the dock door, an event can be triggered to indicate that an item has been shipped.
Can RFID be enhanced with other technologies?
Yes, here are a couple of examples.
Most RFID readers have support for external triggers. These General Purpose Input and Output (GPIO) capabilities can either receive or send events to external hardware. For example, a Reed Switch can be used to trigger the detection of an opening or closing door (input or GPI). Or, a door can be unlocked when an authorized person presents her RFID badge (output or GPO).
Through software, other technologies can be paired with RFID to create additional functionality. For example, when a Bluetooth Low Energy (BLE) Beacon is present, the beacon can represent a zone of proximity to the RFID tags. More specifically, the presence of a beacon can mean that I am near a certain manufacturing area or room. This information can be used by an RFID reader to associate tags with a location.
The basics of RFID are straightforward, but understanding the details of RFID requires a lot of learning. We have only touched the surface of RFID questions and answers. To learn more, you can refer to these resources:
RFID Wikipedia Page: https://en.wikipedia.org/wiki/Radio-frequency_identification
RFID News and Education: https://www.rfidjournal.com/
RAIN RFID documents: https://rainrfid.org/resources/documents/
EPC UHF Gen2 RFID: https://www.gs1.org/standards/epc-rfid/uhf-air-interface-protocol