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How Can I Deal With Stray Reads?

Posted By RFID Journal, 01.10.2020

Are there any cost-effective options for eliminating bounce reads of passive tags? The one supplier I found wanted $115 per square foot, which would not be practical for most portal installations.

—John,

———

John,

There are a variety of ways to deal with stray reads. You may be able to turn down the antenna gain to reduce the reader's range without affecting your ability to read tags coming through the portal. Another option, if you know what tags are expected to come through the portal, is to use software to filter out stray reads. In other words, if you know that only tags with serial numbers starting with 123 should be going through the portal on a given day, then you can filter out or ignore tags that start with 345.

If those options don't work, a simple Mylar curtain should do the trick. RF energy will bounce off the Mylar, eliminating stray reads. Note that some antennas are designed to emit energy in opposite directions. If you are using one of these, you should replace it with an antenna designed to emit energy only in a single direction.

—Mark Roberti, Founder and Editor, RFID Journal

USER COMMENTS

Vladimir Boryaev 2020-01-15 01:18:13 AM
John, I agree with Mark – there are a lot of way to reduce stray reads. Can I offer one more way: «guaranteed number of readings». Normally you read tags inside your portal or tunnel minimum 4 and more times (each tag). But stray reads occur 1-2 times. If you implement inside your software functionality = Tag is read (and go into your database) only if it was read “X” times during “Y” milliseconds. Example: if some tag was read 4 times for half second – number of this tag goes to database (or your software). This functionality helps us a lot to stop stray reading. And one more way. If you use only same tags in your company and all tags are stable (they have reading deviation not more than 10%) you are able to use «signal strength» filter. For instance: if all tags inside your gate or tunnel have «signal strength» RX -40 -50, but stray tags have RX -60 -70. In this case you are able to implement into your software «signal strength» filter and stop or reduce stray readings. Best wishes, Vlad
Harley Feldman 2020-01-16 10:29:06 PM
The way we deal with stray reads is through an algorithm measuring RSSI (Relative Signal Strength Indicator). If two or more of our readers see the same tag, our RSSI algorithm determines which reader the tag is closest to. We do this with every tag read eliminating the need for any shielding.

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