We would appreciate a recommendation for an RFID system with the following functionality: This system should detect certain items in the range of 20 meters (66 feet), and the controller (base) should alert someone as soon as any tag gets out of range. What would you suggest?
Active RFID-based real-time location system (RTLS) solutions can detect items from a distance of 100 meters (328 feet) or more. It is possible to identify zones in most RTLS solutions, and to create alerts if an item leaves a particular zone. There are a few points to consider, however.
One is the object’s size. If it is a wheelchair or a forklift truck, an active tag would be fine. These tags are fairly large because they have a battery and a printed circuit board, so they might not be suitable for a smaller item. In addition, most RTLS offerings are accurate to within about 10 feet. If your application requires you to know, with certainty, that an item is 1 foot outside the zone, then you would likely need an ultra-wideband (UWB) system, which is a form of active RFID that uses multiple frequencies to overcome the issue of multi-path and achieve greater location accuracy.
If the items you are tracking are smaller and less expensive, you might be able to use a passive ultrahigh-frequency (UHF) system. New overhead readers allow you to detect the locations and movements of tags within a defined area. The issues with passive RFID overhead systems are that you would need multiple readers with overlapping read zones to cover a given area, and the read zone would not be precisely defined. You would not be able to draw a line on the floor and say, for instance, that a tagged object was 1 inch inside or 1 inch outside the line.
The best solution depends on a variety of factors and your application requirements. Without knowing more about what you are trying to do, it would be difficult to recommend the best solution, but I would suggest investigating both options above to see which best meets your needs.
—Mark Roberti, Founder and Editor, RFID Journal
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