RFID: Hold it Right There!

Sept. 1, 2006
Consider using RFID to track items and assets that aren't moving.

Okay, a lot of the attention on RFID has been to show that it can be used to increase efficiencies by tracking items as they move through the supply chain. But have you ever stopped to think how useful it could be for things that aren't moving?

You can look at this two different ways— and both are valid—things that should be moving but aren't, and things that have moved that you can't find.

In the first case, it may simply be a matter of using the data you already collect from RFID-tagged (or even bar code labeled) items to flag exceptions. Whenever a tagged/labeled item passes a read point, it is read, recognized and recorded. But if it has stopped moving through your facility, it won't be read.

Most systems are designed to provide exception handling when a tag or label doesn't read but not nearly as many are designed to look for something that isn't there. For example, if a pallet of material is received but is never recorded as "stored," it essentially "disappears" from the system. You may know (or are fairly certain) you have it, you're just not sure exactly where it is. And, unless the system is designed to look for incomplete moves or transactions on a routine basis, you might not know that you don't know where it is.

The problem could be logistical, operational, equipment failure or even communications. But whether the problem was that the pallet couldn't be stored immediately and was put in a "temporary" location then forgotten, the lift truck driver neglected to read the tag/label, the tag/label was damaged or the reader failed, or the WiFi or wired network went down, the lack of data should point you to the problem area and the probable location of the pallet. For items smaller than a pallet, the problem of locating them gets larger.

However, even large items—typically facility assets—that move on a regular basis can be problematic. Medical equipment (such as infusion pumps, wheelchairs and gurneys) is a classic example of this type of asset but industrial equipment (such as mobile safety devices, mobile welding carts or tanks, bins, totes and racks) can be equally difficult to track and locate.

Even if one of these items passes through a reading location, that information may not be sufficient to actually locate it.

In this case, a real time locating system (RTLS) could provide the answer. RTLS uses active RFID tags that periodically broadcast their identity and typically communicate to a receiver on a WiFi backbone. The period between broadcasts can be set by the user depending upon how often the item location needs to be updated. Less frequent transmissions extend battery life. More frequent transmissions help locate frequently moved items.

When a tag broadcasts its identity, one or more readers picks up the signal and records the tag's location. One antenna may be sufficient for confined spaces such as storerooms or corridors since an employee just needs to be directed to the right vicinity. For larger areas, two antennas can give relative position along a line. Three or more antennas provide more precise location data.

RTLS tags can also be temporarily attached to incoming material that may need to be stored in a large, open area. When material is picked, the tag can be removed and reused.

Whether you're trying to track things that should be moving but aren't or things that are difficult to find, there will be an expense involved. And, while no one likes to spend money these days, consider the expense of labor looking for—or having expedited replacement of—material that's gone "missing."

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