How can I be sure the tags are being read?
Accuracy usually refers to the ability to locate tags. I think what you are really asking about is reliability—how consistently you can read tags on metal. The answer is that it depends on the tag. If you were to stick a generic RFID label on something made of metal, you would not be able to read that tag because the metal would detune the antenna. However, if you purchased a tag designed to work on metal, from companies such as Omni-ID, William Frick & Co., The Tag Factory, Xerafy or several others, it would likely work 100 percent of the time. The read distance might even be greater on metal than when read in free air, in fact, since the tags are designed to have energy reflect off the metal to the back of the antenna, in addition to the energy hitting the antenna’s front.
—Mark Roberti, Founder and Editor, RFID Journal