What is the best tag, antenna and reader to use to determine the number of spare parts stored inside a carton?
That's a difficult question to answer without knowing more information about your particular application. You could use passive ultrahigh-frequency (UHF), high-frequency (HF) or low-frequency (LF) RFID tags. HF and LF tags have a short read range (within 3 feet). One of the big questions I have is whether the parts are composed of metal, plastic or some other material. Metal can make it difficult to read passive RFID transponders, while LF tags have the best performance in the presence of metal.
If you want to use EPC-standard technology and achieve a longer read range, then you will likely employ passive UHF technology. If the parts are made of metal, you will need special metal-mount tags. If they are subjected to extreme temperatures, you will need a tag that can survive such temperatures. If they are small metal parts packed closely together within a box, you might have trouble reading the tags, no matter what type of tag or reader you use. If they are metal parts with a lot of air or packaging foam around them, it might be much easier to read the tags.
In terms of choosing a reader antenna, the choice is not so much about brand as the type of antenna. Some passive UHF antennas are linear-polarized, meaning they direct the energy in a thin beam, while others are circular-polarized. They emit energy in a kind of spiral. If the parts are stacked inside the box in a specific orientation, then you can utilize a linear-polarized antenna and align the beam with the direction of the tag antennas (horizontal or vertical). If the parts are in random orientation, then you will want to use a circular-polarized antenna.
There are many readers on the market that will likely meet your needs. You will want to make sure the reader is certified for use in your country or region, and that it performs well enough to read your tag. Like cars, there are high-performance reader models, as well as others designed to be lower-cost and work in less challenging applications.
—Mark Roberti, Founder and Editor, RFID Journal
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