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What Problems Does Aluminum Pose With Regard to UHF RFID?
I have heard that the technology doesn't work well with aluminum since the metal is used as a conduit. We store aluminum shapes (tubes, angles and extrusions). If each bundle has a tag on it, and if two bundles are together, is it true that an RFID system might read only one and not the other?
There are two issues you would face when tracking any object made of metal with a passive ultrahigh-frequency (UHF) RFID system. The first is that the metal would detune the antenna, so if you took an ordinary passive UHF RFID label and affixed it to a piece of aluminum, the metal would detune the antenna greatly, reducing the range from which you could read the tag, or even rendering it unreadable. This is akin to taking a metal coat hanger and touching an AM or FM radio antenna. Instead of a clear signal, you would get static. To overcome this issue, you would need to use a special on-metal tag. There are many different types of on-metal tags available, including tags that can be printed with an RFID label printer.
The second issue involves shielding or blocking the signal from the reader antenna from reaching the tag, or vice versa. If one tagged bundle of aluminum products were behind another, it might not be possible to read the tag—however, I would not say this definitively. It would depend on how tightly the bundles were packed, as well as whether the signals could get to and from the tag from a different direction. You could bounce the signals off of the metal backing of a shelf, for example.
I hope this answers your question.
—Mark Roberti, Founder and Editor, RFID Journal
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