How Much Information Can I Store When Tagging Small Items?

Passive high-frequency (HF) or ultrahigh-frequency (UHF) RFID transponders that would fit your application cost anywhere from 10 cents to 30 cents apiece, depending on the volume purchased (if you buy 1 million or more, the price of each UHF tag would be around 10 cents). Putting them on pens and pieces of paper might prove to be very costly, and not worth the effort. What's more, you would need a different-shaped tag for a pen, which is long and narrow, than you would for a book or a piece of paper. Specially designed tags would be more expensive, and if you also wanted the tag to be embedded in a bar-coded label, that would increase the cost even more.

But to answer your question: Passive HF and UHF tags based on the Electronic Product Code (EPC) standard have blocks of user memory allotted that you can use to write data to a tag. This either can be locked, so that it can't be changed, or it can be rewritable. Different types of RFID transponders can hold different amounts of data, but you can buy UHF tags with up to 32 kilobytes of memory, which is equivalent to roughly 16 typewritten pages.

You won't be able to write the same information that is on the tag to the reader. Instead, that data is stored in a database. Each object's serial number is associated in the database with information regarding that particular item. So the database would tell you, for example, that tag 12345 was on a specific book.

As for tag range, it really depends on the type of RFID system that you are using. It can range from 1 millimeter (0.04 inch) for a small 2.45 GHz passive tag, to 1,500 feet or more for an active (battery-powered) tag. If you use passive UHF tags—which is what I discussed above—the read range would be from 3 feet to 75 feet, depending on the tag model chosen. Small labels that might be placed on a pen would have a short read range, whereas large devices, such as Omni-ID's Ultra tag, can be read on a shipping container from a distance of 75 feet.