Can RFID Sound an Alarm If Two Items Are Separated?

By RFID Journal

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Ask The ExpertsCan RFID Sound an Alarm If Two Items Are Separated?
RFID Journal Staff asked 8 years ago

Is this use of the technology possible?

—Name withheld


It depends on what you are trying to achieve. If you have two tagged items within an area covered by a reader antenna, you could have the reader issue an alert if one item were to leave the read field. Ordinary passive ultrahigh-frequency (UHF) antennas, however, do not give you a perfectly defined read field. So if a tagged item were to be moved to the edge of the read field, it would likely be interrogated sometimes and not at other times.

If the defined area is a small section of a shelf—say, 4 square inches—then a high-frequency (HF) reader can provide a well-defined read field. This would allow you to set up software to alert you if an item left that 4-by-4 space.

If the items are large and of high value, you could use an active ultra-wideband (UWB) system. UWB provides the greatest location accuracy of any RFID system, down to a few centimeters. So you could put a tag (which costs around $50) on each item and set up software to sound an alarm if the items moved more than, say, a foot apart.

—Mark Roberti, Founder and Editor, RFID Journal

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