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How Accurate Can RFID Tracking Be?
Does the technology offer high accuracy for monitoring items?
There are two different meanings of "accurate" in the context of RFID tracking. One issue is read accuracy. That is, if you have 100 tagged items, how many tags will you be able to read? If you push the items through a portal and read 99 of them, it is said that your read accuracy is 99 percent. We also talk about location accuracy, which means this: If there is a tagged item at a specific location, how accurately can we pinpoint its location? Can we locate the item on a facility map to within 10 feet or 10 inches? Since I do not know which type of accuracy you are referring to, I will address both.
Read accuracy depends on what is tagged, how it is stacked, the types of systems being used and so forth. If you use active tags, read accuracy is usually 100 percent, since the tags broadcast their information like a cell phone. Passive tags are subject to interference, and if the signal is blocked by metal, the tags cannot be interrogated. So, you might read 99 percent of the tags on RF-friendly clothing, but you would not be able to read tags on cases of Coca-Cola in the center of a pallet of the beverage.
Location accuracy also depends on the type of RFID system that you choose. A passive RIFD system tells you only that a tag is in the read field, so with a passive high-frequency (HF) system, you would know a tag was within about 3 feet of a reader. With a passive ultrahigh-frequency (UHF) system, you would know that a tagged item was within 20 to 25 feet of the reader antenna, and perhaps no more than 10 feet to the left or right of that antenna.
Active tags can tell you that an item is within 300 feet of a reader, but there are also active RFID real-time location systems (RTLS) that can triangulate on a tag and tell you its location to within 10 feet. Active ultra-wideband (UWB) systems can tell you the location of a tagged asset to within a few centimeters. This is because UWB systems compensate for something called multipath, which can affect the ability to determine a tagged asset's location.
—Mark Roberti, Founder and Editor, RFID Journal
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