Which RFID Reader Would Give Us 100 Percent Read Rates?

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Ask The ExpertsCategory: QuestionsWhich RFID Reader Would Give Us 100 Percent Read Rates?
Mark Roberti Staff asked 6 days ago

We are trying to reduce theft by reading the tags on all items placed on a truck. But when we attempt to read the tags on those goods inside the vehicle, we cannot achieve more than 80 percent read rates. What model of RFID reader would allow us to read all of the tags all of the time?

—Roger

= = =

Roger,

There is no RFID reader that can capture the ID number of every tag on every item every single time. Passive UHF RFID tags offer a great advantage over other Internet of Things devices since they have no battery, but this means it can be challenging to get energy to every tag to power it up and receive a response.

If you were to put a passive UHF tag on a case of Coca-Cola cans, for example, then stack that case in the middle of a pallet containing multiple cases, you would not be able to read the tag with any reader. This is because the metal of the cans around the case in the middle would prevent energy from reaching the tag at the center of the pallet. To achieve high read rates, you must have the right tag and reader, the proper tag placement and the correct reader antenna setup.

Tags: Some tags are made for being read on metal items. Some are designed for short-range reading of items on shelves, and others for longer-range reading in a warehouse. Some tags are meant to be read in a specific orientation to a reader. Others are built to be read in any orientation. It’s important to select the right tag for your specific application.

Placement: You’ll need to place each tag at a location on an item where it can be read. If a tag isn’t designed to work on metal or near water, it should be affixed at a spot where there is no metal or water present, such as at the neck of a bottle. If items are stacked, the tags should not all be in the same place on those products, because a tag placed in front of another will block energy from reaching the one behind it.

Readers: While some RFID readers are clearly better than others, most passive UHF readers will be able to read a tag in free air from roughly the same distance and achieve somewhat similar read rates in ideal conditions. But you would need to determine whether you should use a handheld, fixed, tunnel or overhead reader for your particular use case.

Antenna setup: If the reader antennas are not positioned correctly, the items might not remain in the read field long enough to receive sufficient energy to reflect back a signal to the antennas. In addition, it’s more difficult to interrogate tags on stationary items than it is for those that are moving, so it may be easier to read tags on goods as they move through a portal than if they were sitting on a loading dock.

It’s important to consider what you are trying to achieve and to then design the system in a way that will get you the results you want. I don’t know what technologies or processes your firm uses to move goods, but if pallets are involved, you could build the pallet, read all of the tags, shrink-wrap the pallet and affix a tag to the outside of the wrap. If you were to then read the pallet tag, you would know how many items were associated with that particular pallet. And if the pallet arrived with the shrink-wrap still intact, then you would know that no items had been removed and could thus confirm that the right number of items had arrived at the store.

Mark Roberti
Founder and Editor
RFID Journal

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