Can Passive Transponders Quickly Count Items Moving From a Factory to a Store?

By RFID Journal

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Ask The ExpertsCan Passive Transponders Quickly Count Items Moving From a Factory to a Store?
RFID Journal Staff asked 9 years ago

I would like to mount a "bridge" of passive RFID readers in a garage door, and have small trucks carrying 6,000 lingerie items tagged with passive ultrahigh-frequency (UHF) RFID transponders. The goal would be to ensure that the number of items leaving the factory was the same as the number delivered to the shops. Is this possible?

—Name withheld


It would certainly be possible to employ passive UHF RFID transponders to quickly count items leaving a factory and the amount arriving at a store. I cannot say for sure whether it could be done in the way you are proposing, though. There are a couple of issues that would affect your ability to read 6,000 items leaving the factory.

One issue would be the truck's speed. If it were passing through the reader portal very quickly, there would be insufficient time to interrogate the serial number of every tag on all 6,000 items. Another issue could be how densely the items—and, thus, the tags—were packed. If the tags were in close proximity to one another, this could affect the system's ability to read them, since one tag could prevent energy from reaching another.

A third issue would involve the material from which the truck was made. If the truck had an open area in which the lingerie items were kept, then this would not be an issue. But if the truck had a metal or aluminum storage area in which the clothing items were stored, then the RF energy would not penetrate the metal and reach the tag.

In most cases, I have seen companies conduct inventory counts of clothing items on a rack either by pushing the rack through a portal or waving a handheld reader around the tagged items. In both cases, workers might need to manipulate the items a bit by hand, in order to ensure that all tags were read. It might take 30 seconds to read all 6,000 tags on items leaving a factory and another 30 seconds to read the items arriving at a store.

I would suggest working with a skilled systems integrator to set up and test a portal to determine if you can read all of the tags. Try having the vehicle stop for a moment if all of the tags are not read. If you cannot interrogate all tags consistently, you might need to use the method I describe above.

—Mark Roberti, Founder and Editor, RFID Journal

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