RFID Tag Selection Guidance
To select the most appropriate RAIN RFID Tag for your purpose, it is important to identify some key requirements. These requirements consider both the actual performance of the Tag and the environmental factors in which the Tag will be used.
RFID tags are mainly used to identify objects. These objects, therefore, have or will have a digital identity, or a code that simply identifies them. This code can pre-exist the Tag or be associated later. Very often, the syntax developed by GS1 is used for the electronic product code (EPC - Electronic Product Code). The most used scheme is SSCC-96, which requires at least a 96-bit memory for the EPC. This requirement is met by all RAIN Tags produced by Impinj, NXP or Alien, you can find on this website.
However, sometimes a different type of scheme may already be in use, or it may take longer for the EPC. In this case, you need to opt for UHF chips with more memory dedicated to the EPC, such as the Impinj Monza 4E, or the NXP UCODE G2iL, G2iM+, or the UCODE 7xm.
There are two mechanisms for securing Tags that are closely interrelated.
- Passwords: required to perform certain actions.
- Locking: defines what can be done with and without a password.
The RAIN RFID tags have two passwords.
- Access password: used to (prevent) reading and writing specific memory banks in the chip.
- Kill password: used to (prevent) chip neutralization. A killed tag no longer works, so it is important that only those who know the password can neutralize it permanently.
Not all chips have passwords, as this is not mandatory according to the standard. For example: the Impinj Monza R6 chip does not have access and kill passwords, which means that the chip cannot be protected from writing or killing. The Impinj Monza R6-P and R6-A chips still have access and kill passwords. The lock command is a mandatory requirement in the RAIN standard.
The performance characteristics that determine the detection/identification/traceability of a tagged object are a crucial point in choosing the Tag.
First of all, please note that the real reading distance varies according to different factors:
- the size of the Tag (in particular its antenna);
- the type of chip (in particular its sensitivity);
- environmental conditions;
- the object on which the Tag is placed;
- the RFID Reader.
As you can see, not all these factors actually depend on the Tag. Regarding the dimensions, it must always be kept in mind that a larger antenna corresponds to a greater reading distance. As for the chip, it is good to choose those with a lower sensitivity. The best chips, from this point of view, are those that belong to the most recent UHF "families" NXP UCODE 9 and Impinj M730 / M750.
When implementing an RFID system, it must be kept in mind that there are materials that negatively interfere with radio frequencies. These materials are metals (and in general all conductive materials), liquids and the human body.
All non-radiolucent conductive materials, such as metals, can create the Faraday Cage effect, which prevents the RFID Reader from detecting the Tag. To overcome this problem, special Tags have been designed, called Anti-metal, or On-metal Tags, which guarantee a good reading even if applied above or behind metal surfaces.
Furthermore, UHF frequencies are attenuated by liquids. However, there are transponders that can be applied to liquids with suitable insulating materials.
As for the human body, we must consider the possibility of positioning the Tag "on sight", so that the interference is reduced to a minimum.
There are several standards that govern the use of UHF RFID frequencies worldwide. The two main ones are: ETSI for Europe and FCC for the United States and North America. While the protocol remains the same, the frequency and the technique to communicate with the Tag are different. This involves some precautions in choosing the reader and RFID antennas, but also in the Tags. Generally, RAIN RFID Tags are compatible with both standards, but it is always a good idea to check. Furthermore, depending on the standard used, there are different performances.
Now, a less technical and more practical question: how to apply the Tag to the item. The most common format of an RFID tag is the Wet inlay, which is a very thin adhesive label.
If the Tag has to be applied in more hostile environments, for example outside, or in industrial contexts, with high temperatures or subject to humidity, contact with chemicals or other substances, there are more resistant RFID Tags, with better glues or with holes to be fixed more firmly.
Last but not least, it is necessary to assess whether additional printing or customization is required. For example, with regard to labels, it may be necessary a barcode, or to be printed or programmed with an RFID printer. In this case, it is necessary to evaluate the specifications of the printer in use.
Not all types of tags can be customized, and in any case not all in the same way. So, if this is a crucial element, you need to check before buying.
Although this guide has been written to be as accurate as possible, it does not replace the expertise and the advice of an expert in RFID solutions. For more information, please contact us.