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What Is the Smallest Tag That Can Be Read From 10 Feet Away?
Could a tag the size of a postage stamp be read indoors from that distance using a low-cost reader? Are tags powerful enough yet to do that?
RFID tags don't have power—they reflect a signal from a reader. Read range depends on a number of factors; some relate to the tag, and some don't.
On the tag side, one factor is the efficiency of the tag chip—whether it can use power from a reader efficiently enough to reflect back a signal that can be picked up by that device. Another is tag antenna size; a larger antenna enables a tag to "harvest" more energy from a reader and reflect back a stronger signal that can be read from further away.
There are also factors that influence read range that have nothing to do with the tag. One is the reader antenna's sensitivity power. All readers are limited in power output by the Federal Communications Commission (FCC) in the United States, the European Telecommunications Standards Institute (ETSI) in Europe and other regulators in Asian and Latin American countries. But power can be dialed down, and handhelds usually have reduced power output that limits range. Other issues include how sensitive the reader antenna is (whether it can pick up a weak signal from far away), the materials you are trying to read through, what other "noises" are in the environment, and so forth. For this reason, it is impossible to say that a given small tag can be read from 10 feet away.
There are certainly a variety of tags you could test on your objects. Avery Dennison produces a variety of small tags, such as the AD-805, which measures 16 millimeters by 16 millimeters (0.6 inch by 0.6 inch); the AD-814, which measures 22 millimeters by 22 millimeters (0.9 inch by 0.9 inch); and the AD-828, which measures 15 millimeters by 40 millimeters (0.6 inch by 1.6 inches)—click here to see a list of the company's tags. Alien Technology's ALN-9629 "Square" inlay measures 22.5 millimeters by 22.5 millimeters (0.9 inch by 0.9 inch)—click here to see a list of its tags. And Invengo, UPM RFID and other companies make small tags as well.
I would suggest you try to get samples of those that fit your size requirements, and test them. Under good conditions, some of the above tags can be read at a distance of 10 feet.
—Mark Roberti, Founder and Editor, RFID Journal
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