I'm looking for a way to detect the user closest to a certain object that has the RFID reader attached to it. Therefore I need my RFID reader to restrict itself to the user closest to it and not read any other tag. I'm open to using other technologies too.

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    \$\begingroup\$ I'm pretty sure this is impossible with passive RFID alone. \$\endgroup\$
    – Hearth
    Jan 18, 2019 at 16:24
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    \$\begingroup\$ Doesn't the reader have to read the tag to know if it's THE tag?? \$\endgroup\$ Jan 18, 2019 at 16:25
  • \$\begingroup\$ Is this possible with any other technology then? I want this functionality but I'm not really sure about how I should go about it? \$\endgroup\$
    – Htnamus
    Jan 18, 2019 at 16:29
  • \$\begingroup\$ Don't ask a new question in the comments. If you want to ask a different question, make a new question. \$\endgroup\$ Jan 18, 2019 at 16:40
  • \$\begingroup\$ Before you write up a second question, it appears you have a specific purpose in mind and reason for wanting this functionality, so you should describe your form factor and use case. If you want an idea why, google "XY problem stack exchange". \$\endgroup\$
    – K H
    Jan 18, 2019 at 23:30

1 Answer 1


An RFID reader can't guess distance, and especially not until trying to "read" a tag.

Some RFID standards (there's different ones, do your research what fits your purpose best) allow for collision avoidance; but those basically "partition" the ID space to "detangle" interaction.

But physically, an RFID reader has no way of knowing which tag is closest. Sure, it might have an option to guess based from signal strength, but that's pure guesswork and won't work well with different tags in different orientations and different media in between reader and tag.

If "closest only" is a strict requirement, you'd probably have a use case for optical technologies like bar codes or text labels.


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