It
is worth noting that although using barcodes for tracking is a slow and manually intensive
process, it is rare to miss a read other than by human error. With RFID tags, this human
element can be eliminated but unfortunately, the technology usually cannot guarantee
100% accuracy in real-world applications.
Read accuracy at a portal obviously depends on factors such as the quality, reliability, and
capabilities of the tags and readers used, as well as the speci?¬?c application domain. However,
when considering a ?¬?xed technology (tag=reader) and application, the design of the
RFID-equipped portal becomes critical. Tag reads can be missed because of many factors
including limitations in the read range, tag orientation, or interference (from water, metal, or
other tags). Another complicating factor is that in an automated RFID-scanning process the
locations of tags are often not ?¬?xed because items are of different sizes and might be moving
on a truck, or material-handling equipment such as a pallet, forklift, or conveyor belt. In fact,
not only the location but also the orientation of each tag may differ when the interrogation
process starts within a portal??”this is especially true with item-level applications.
To compensate for the problem of imperfect read-rates, multiple reader antennas are
commonly used in portal design, and a major determinant of read accuracy is the correct
placement of reader antennas at the portal.
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