Performance. Everyone knows there are requirements for 100% read rate for RFID pallet tags on receiving and cartons on conveyors. The distance requirements are also well known. We're not going to review those requirements here because if you don't know, either you're not supplying Wal-Mart or the Department of Defense (DoD) and you don't need to know right now, or you're in serious trouble.
What we will look at is how to achieve reliable performance. The first consideration is the antenna design. Dipole antennas tend to produce a cigar-shaped field, in other words, directional. This isn't necessarily bad but it's not going to produce a nice omnidirectional field. For that, you need an X-shaped (or other complex shape) antenna. These produce omnidirectional fields.
These fields, however, are affected by the next "P," and your selection of the antenna design here may depend on it.
Product. You're probably already aware that both metal and liquids are problematic for UHF RFID so if you're shipping cans of liquids or electric motors, for example, you know you have to be careful. But metal and liquids show up in a surprising number of places. Produce, for example, typically has a high water content; rice typically has a high iron content; shoes can contain metal stiffeners in the soles or toes; and so on.
The point here is that these problematic substances are generally known by those shipping them but are often overlooked as considerations when placing RFID labels. Finding, or providing, adequate air space over which to place the RFID label may require some thought.
Placement. If you're shipping materials that will absorb RF energy, you may have to carefully consider where to put the label. Here's where both product and antenna design come into play.
If you're shipping, say, cans of oil, there's a natural air space next to the carton between adjacent cans. Using an omnidirectional antenna will bring the field into contact with the metal and liquid, not a good thing. A dipole antenna mounted parallel to the cans, however, may have enough air space to avoid adverse effects of the product.
If you're shipping to the DoD, of course, you should consult the latest draft of MIL-STD 129 for placement requirements.
However, for non-DoD requirements, customer requirements and performance criteria are the rule. Most want the long side labeled although there is growing sentiment for placing the label on the top of the shipping container. In other words, your bar code shipping label and RFID label may be in different places.
Privacy. Actually, this is both privacy and productivity. Most people have at least heard about the furor over privacy concerns brought about by the HP printers being sold at Wal-Mart and Sam's Club --complete with the Wal-Mart mandated RFID label on the shipping container which just happened to be the point of sale unit.
Now, aside from the fact that most of the concerns expressed by privacy advocates are based on entirely mythical properties for RFID labels and the fact that you don't need a fancy RFID scanner to see who's carrying the big box with the HP logo on it, privacy concerns and productivity share a common requirement: locating the darned thing on the box.
Having the RFID label clearly identified (so that consumers know it's there and can remove, deactivate or destroy it) addresses many of the privacy advocates concerns.
However, even if you don't sell into retail, you can address these privacy concerns and reap a benefit in the supply chain at the same time. A clearly identified RFID label tells employees not only where the RFID label is but that it's there to begin with. Knowing a label has an RFID transponder means that employees don't waste time trying to read something that's not there.
Addressing these "Ps" may not be quite as problematic as you might think.
There are two free documents available from AIM Global to help you address placement and privacy issues. AIM is the world-wide trade association for manufacturers and suppliers of RFID and other automatic identification and data collection technologies.
The first document offers RFID labeling guidelines developed by AIM's RFID Experts Group (REG). While intended as recommendations for the DoD, it is the best information on general labeling considerations currently available. (The REG is nearing completion of a commercial supply chain version of this document but, in the interim, the DoD-centric one is still extremely useful.)
AIM has also published the "AIM RFID Mark" standard. The AIM RFID Mark document defines a standard mark to be used on labels as well as printers and readers that 1) graphically represents an RFID transponder as a visual aid in finding the appropriate label, and 2) contains a two-character code that identifies the transponder type, frequency and the authority for the data content (e.g., EPC). The AIM RFID Mark has been received enthusiastically by privacy advocates as a very positive step in addressing notification concerns.
Both documents are free downloads from the AIM Global web site (under the "Download" section). Graphic files for the AIM RFID Mark are also included to simplify implementation.
Bert Moore
| REG Label Guidance: AIM RFID Mark: |
