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How to choose an RFID tag?

Each RFID tag has a set of characteristics by which its physical and environmental limitations can be determined for a given application. With respect to the requirements of a specific RFID system, these limitations help narrow the search and find the optimal tag for a given application.

What factors should we consider when looking for an RFID tag for our project?

1. Frequency of the tag

Passive RFID tags operate at LF, HF and UHF RFID frequencies.

In the most general terms, the higher the operating frequency, the faster the reading speed and the longer the tag reading range, while lower frequencies are more resistant to interference.

We will use LF tags wherever we read single objects at close range.

HF tags will enable us to take readings from a distance of up to one meter. They offer higher memory capacity than LF tags.

UHF tags have the highest reading speed - hundreds of reads per second, and are read from the greatest distance - up to 35 meters. They will prove useful in all those applications where there is a need to read multiple tags from a distance of more than one meter.

When selecting RFID tags for an existing RFID system, we must choose tags that are compatible with that system. LF RFID readers will not be able to read UHF RFID and HF RFID tags.

We must also keep in mind the standards that apply in each country. For UHF RFID frequencies, the applicable European standard is the frequency range of 860-868 megahertz, for the United States 902-928 megahertz. If we buy a reader designed for the U.S. market and not for Europe, it will not read UHF RFID chips, which operate only in the European band.

2. Environmental conditions to which the tag will be subjected

If it will be exposed to high temperatures (above 85 degrees Celsius), dust, water, detergents in repeated cleaning processes, will be subjected to laundry processes, will be exposed to high pressure, shock, etc., it is necessary to select such a tag that will survive in these specific conditions, or even is specially adapted to them, such as Omni-ID high-temperature tag, Fujitsu laundry tag.

In secure indoor environments, such as tagging office equipment for inventory purposes, less resistant RFID tags can be used for tagging, while industrial conditions require the use of a hard-cased tag.

RFID tags can also be used in all those applications where the tag is treated as a one-off - it is read only for the purpose of some single process, such as order picking, and is not used later.

3. Material of the marked object

Each RFID tag is designed to attach to a specific substrate. RFID tags generally work well on materials such as plastic, wood, cardboard, but only some will work well on metal, liquid-filled objects or glass. Tags that work on metal and that are not bothered by the presence of liquid are generally more expensive than standard RFID tags.

4. Amount of available space on the tagged object: maximum dimensions of the tag

RFID tags are available in a variety of shapes and sizes to better suit the requirements of a project. The amount of space on the object to be tagged can be key to selecting the right tag. Some applications require tags in a really small size, such as the tagging of surgical instruments.

Also note that in UHF RFID tags, the dimension of the tag's antenna, and therefore ultimately the dimension of the tag, is important to its read range. The smaller the antenna, the smaller the tag, the smaller the read range of that tag.

5. The fifth issue is how to attach the tag

The optimal attachment method depends on several factors: whether the tag will be exposed to environmental factors, what material the tagged object is made of, what shape it has. 

The available mounting options, as a rule, are specified in the tag specifications. This generally applies to tags in hard cases. Since RFID tags are essentially self-adhesive, there is only one attachment method. As for how to attach hard tags, there are many options:

  • screws, rivets, staples – many tags have special mounting holes for their use,
  • zip ties,
  • various adhesives, epoxy resins,
  • embedding the tag in the object to be marked, such as milling a hole in a metal surface, inserting the tag there and encapsulating it with epoxy resin,
  • welding,
  • ultrasonic welding

6. Required tag reading range for the project

The reading range depends on the frequency at which the tag operates, and in the case of UHF tags it depends on the size of the tag - small tool tags have a small reading range, such as Fit 100 - 1.1 m.

Large container tags much larger: Dura 3000 – 35 meters.

The reading range of a tag given in its specifications is the maximum range. The reading range obtained in real conditions is influenced by the reader's power, antenna gain, tag position, and environmental conditions.

7. Tag's memory capacity

In standard designs, only a number is stored in the tag, with other information about the object stored in the database associated with it. However, the specifics of a given application may require storing more information in the tag itself, in which case you should choose a tag on a chipset that offers more bits of memory, such as Higgs 3 has a 96-bit EPC, 64-bit TID and 512 bits of user memory.

8. Personalization and programming of the tag.

If a particular project requires a company logo, barcode to be visible on the tag, you need to choose a tag that has this option. Usually, personalization of the tag is an additional fee.

As for programming the tag with a specific number, all UHF RFID tags are programmable and the information stored in them can be changed repeatedly. The programmed information can also be protected with a password to prevent unauthorized people from reading and changing the information.

Considering all of the above will help select the perfect tag for our project.