Can RFID Inventory Tagged Parts Within a Cage?

Published: November 4, 2009

Is it feasible to scan an entire cage full of RFID-tagged parts, and then have the cage report a quantity by item number (counting inventory, finding containers contaminated with multiple item numbers and so forth)?

—Name withheld

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It is difficult to answer your question without knowing the size and material of your cage, the number of parts, the materials those parts are made of and so on.

If the cage is composed of metal, and the parts are metal, small and densely packed, then it could be difficult to read passive RFID tags on every part, every time. The metal parts might detune the antennas of tags on other parts, or block the signal from the reader, which means some tags would receive insufficient energy to send back a signal.

If, however, the parts are larger and there are air gaps between them, it might be possible to read every tag. Omni-ID manufactures small ultrahigh-frequency (UHF) tags that perform well on metal parts. And Magellan Technology makes high-frequency (HF) transponders that can be read in close proximity to one another, so if these are properly mounted on metal, they could work.

A good systems integrator with experience tagging metal parts would be able to help determine the feasibility of your application, or whether there is a suitable alternative, such as reading tags on parts as they are moved into and out of the cages.

—Mark Roberti, Editor, RFID Journal