RFID Frequently Asked Questions

What is RFID?

Radio frequency identification, or RFID, is a general term for technologies that use radio waves to automatically identify individual items. There are several methods of identifying objects using RFID, but the most common is to store a serial number that identifies a product, and perhaps other information, on a microchip that is attached to an antenna (the chip and the antenna together are called an RFID transponder or an RFID tag). The antenna enables the chip to transmit the identification information to a reader. The reader converts the radio waves returned from the RFID tag into a form that can then be passed on to computers that can make use of it.

How does an RFID system work?

The system consists of a tag, which is made up of a microchip with a coiled antenna, and an interrogator or reader with an antenna. The reader sends out electromagnetic waves that form a magnetic field when they “couple” with the antenna on the RFID tag. A passive RFID tag draws power from this magnetic field and uses it to power the microchip’s circuits. The chip then modulates the waves that the tag sends back to the reader and the reader converts the new waves into digital data.

Is RFID better than using barcodes?

RFID is not necessarily “better” than barcodes. The two are different technologies and have different applications, which sometimes overlap. The big difference between the two is barcodes are line-of-sight technology. That is, a scanner has to “see” the barcode to read it, which means people usually have to orient the barcode towards a scanner for it to be read. Radio frequency identification, by contrast, doesn’t require line of sight. RFID tags can be read as long as they are within range of a reader. Barcodes have other shortcomings as well. If a label is ripped, soiled or falls off, there is no way to scan the item.

Will RFID replace barcodes?

Probably not. Barcodes are inexpensive and effective for certain tasks. It is likely that RFID and barcodes will exist together for many years to come.

Is there an issue using RFID around metal and water? 

RFID can be used to track metal cans or liquids. Typically radio waves bounce off metal and are absorbed by water at higher frequencies. That makes tracking metal products or those with high water content problematic, but good system design and engineering can overcome this shortcoming. In fact, there are applications in which RFID tags are actually embedded in metal auto parts to track them.

What’s the difference between active and passive 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. The Auto-ID Center is focusing on passive tags, which cost under a dollar today. Their read range isn’t as far – less than ten feet vs. 100 feet or more for active tags – but they are far less expensive than active tags and require no maintenance.

How much information can the RFID 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.

What is the read range for a typical RFID tag? 

The read range of passive tags 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, 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.

What are some of the most common applications for RFID? 

RFID is used for everything from tracking livestock and pets to triggering equipment down oil wells. The most common applications are tracking goods in the supply chain, tracking assets, tracking parts moving to a manufacturing production line and security (including controlling access to buildings and networks)

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