RFID Tag Application and Performance
There are tag designs that will work with metal in near proximity. They do require a non-metallic "spacer" (e.g., air, cardboard, plastic, etc.—essentially something that puts a sufficient buffer in between items) in order to function properly.
How do you deal with multiple RFID tags on a product—for example, a manufacturer's tag inside the box and my tag on the outside?
All RFID technology being used in logistics applications has the ability to read multiple tags in the field at the same time. The source of the tag should not make any difference providing that the system has been configured to receive the data from the tag. However, the system does need to be designed so that it "knows" which tag to read at a specific event—for example, arrival at a dock door. Many tags have the ability to differentiate themselves using application identifiers that will alert the system as to whether they are an item-, case-, or pallet-level tag.
How well will RFID work in a military manufacturing environment where metal tools, metal weapons, etc. are present?
Again, there are tag designs that will work with metal in near proximity, and the military has found that this is not an impediment to using RFID in specific applications. More information can be found at www.dodait.com.
Does each application require a custom-designed antenna or does the standard tag work for all applications?
If one is talking about EPC UHF Class 1 Gen 2 tags, there are many designs from which to choose, and it is very likely that one of those will work well with your application, unless extreme conditions (for example, temperature or humidity) exist. However the performance of a tag in terms of readability depends on much more than antenna design. In general, the larger a tag's antenna the more likely an interrogator can read it, but read rates between large antennas and smaller antennas are not necessarily dramatically different. Other areas that need to be considered are the tag's ability to extract/consume/reflect an RF signal from an interrogator, whether distance or orientation to the interrogator changes a tag's performance, how nearby materials affect read rates, and the power of the backscatter. The cost and availability of tags needs to be considered, too. It is wise to conduct a number of tests on a variety of products under different conditions to arrive at several tags that match the application.