How Can RFID Tags Be Located in Warehouses When Items Are Removed from a Rack?

Are there any sensors capable of tracking items within a warehouse?

—Anirudh

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Anirudh,

There are generally three ways in which to employ radio frequency identification in a warehouse. One option is to tag pallets, cases, bins or items that are stored on racks. If you need to find one of these things, you can enter into a handheld RFID reader the serial number of the tag associated with the item you want to find. Then, someone can walk around the facility waving a reader in all directions to locate the tagged item. As the reader picks up the signal from the correct tag, it beeps increasingly louder so that you can easily hone in on it. This way of using RFID has the advantage of being low-cost, since there is no fixed infrastructure to install, but it also requires labor to go out and find the tagged unit you seek.

A second option is to put a reader on a forklift truck and tags in the floor or on racks. When a forklift drops off an item at a specific location, the system records the serial number of the object being stored, along with the location of its rack. If you need to retrieve the tagged unit, a pick order is generated by the warehouse-management system with the exact rack, thus saving time required for workers to search for that item.

The last option is to install overhead readers that are always on and constantly interrogating tags. The readers can tell you roughly where a tagged item is, or the location where the tag was last read. Overhead readers often cannot interrogate every single tag within a warehouse every time, because one or more tags might be blocked by metal shelving. But it should provide a general location where an item is located or was last seen.

I hope that answers your question.

—Mark Roberti, Founder and Editor, RFID Journal