RFID System Performance Problems - Liquids, Metals, and More Environmental Issues

Posted by Suzanne Smiley on Mar 31, 2017

Updated April 24, 2024

Liquids, Metals, Florescent Lighting, & Other RF Waves

Deploying an RFID application without consideration of the environment can potentially lead to thousands of dollars spent with less than stellar read rates. If positive results cannot be provided within the required timeframe, the project may be abandoned and the organization deprived of potential time and cost savings.

Whether the RF waves are absorbed (as with liquids) or reflected (as with metals), any source of interference in the environment may cause problems unless properly mitigated.

What’s the Problem with Liquids and RFID?

Liquids absorb RFID energy, which makes it hard for the RFID tag to send back an RF signal (tagging liquid-filled containers) or to receive an RF signal (liquids in the application environment).

How do you Tag Liquid-Filled Containers with RFID?

In the past, it was nearly impossible to tag liquid-filled containers like soda bottles or bottles of laundry detergent because the absorption of RF energy by the liquid would leave little RF energy for the RFID tag to receive, much less to backscatter in reply to the RFID reader. Now, there are quite a few options for tagging liquid-filled containers.

Option: Use Low Frequency (LF) RFID instead of High or Ultra-High Frequency. LF RFID does not have the issues with water that higher frequencies struggle with, so it can be used for animal tracking or water-filled items. The downside is slower data transmission speeds and shorter read ranges relative to the higher frequencies.
Option: Use UHF labels approved specifically for use on water-filled containers like the Omni-ID IQ 600 Labels and the Confidex Silverline.
Option: Use UHF Near-Field tags approved for use on water-filled containers like the Alien SIT tag and the SMARTRAC Trap.
Option: Use regular UHF inlays or labels and place a spacer between the liquid and the tag made from foam, silicon, or another thick material (e.g. the Foam-Backed ShortDipole).

How do you Tag Items in Liquids with RFID?

Impossible with UHF until a few years ago, tagging items in liquids can now be done thanks to the better tag construction and design.

Option: Use Low Frequency (LF) RFID instead of High or Ultra-High Frequency. LF RFID does not have the issues with water that higher frequencies struggle with, so it can be used for animal tracking or water-filled items. Again, the downside is slower data transmission speeds and shorter read ranges relative to the higher frequencies.
Option: Use UHF Near-Field tags approved for use in water-filled containers like the Alien SIT tag. The read range will be very short, but these tags will still read. NOTE: there is no guarantee that this will work consistently for an application; testing is always key.

How do you Deal with Liquids in the RF Application Environment?

Whether the application is outdoors near lakes or ponds, or indoors around water tanks or water-filled machinery, liquid can play a role in an RFID application because it absorbs RF energy.

Option: Use Low Frequency (LF) RFID instead of High or Ultra-High Frequency. LF RFID does not have the issues with water that higher frequencies struggle with, so it can be used for animal tracking or water-filled items. Again, the downside is slower data transmission speeds and shorter read ranges relative to the higher frequencies.
Option: Set up the RFID system with extra hardware to ensure that the necessary RF energy gets to the tagged objects and not significantly absorbed by the liquid. RFID Power Mappers are a great tool for measuring UHF RF energy in any given area and determining if enough energy is reaching the designated read zone.

What’s the Problem with Metal and RFID?

Metal reflects RF waves which can lead to the RFID tag antenna detuning (tagging metal objects) or multiple null zones in your application environment (metal in the environment).

How do you Tag Metal Objects with RFID?

Metal objects were an issue to tag when RFID tags were first being manufactured, but now RFID tag manufacturers have created metal-mount RFID tags that can mitigate that problem and allow for easy tagging of metal objects. For more information on metal-mount tags, read our article about Metal and RFID Metal Mount Tags.

Option: Use metal-mount RFID tags which are produced specifically for tagging metal surfaces. Examples of metal-mount tags are the Omni-ID Exo 750, Xerafy Micro XII, and the Vulcan Custom Universal Asset Tag.
Option: Place an embeddable, metal-mount tag into a drilled or pre-made hole in the object. In some applications, embedding works even better than adhering on the object (such as in rugged environments). When embedding an RFID tag, always leave one side with no metal covering and protect it with epoxy or something similar to ensure it can be read. (NOTE: an RFID tag completely encased in metal cannot be read).

How do you Deal with Metal Objects in the RF Application Environment?

Metal in the environment reflects RF waves, potentially creating null zones where the RFID tag cannot be detected. More metal in an environment will lead to an increased number reflections, ultimately causing multiple null zones.

Option: Place RF absorbing materials in front of metal objects to absorb the RF waves instead of reflecting them back into the environment. RF absorbing materials can be substances like carbon-loaded foam and polyurethane foam.
Option: Set up the system with extra hardware to ensure that the necessary RF energy gets to the tagged objects. RFID Power Mappers are a great tool for measuring UHF RF energy in any given area and determining if enough energy is reaching the designated read zone.

What's the Problem with Florescent Lighting and RFID?

Fluorescent lights, when on, can reflect RF waves causing the same issue as metal - reflected waves colliding with the original RF waves creating null zones.

How do you Deal with Florescent Lighting in the RF Application Environment?

Fluorescent lights can, in some instances, reflect RF waves causing null zones. Fluorescent lights become more of a problem the closer they are to the RFID system or tagged object.

Option: Using RF absorbing materials, such as carbon-loaded foam, between the fluorescent lights and the RFID system will allow the RF waves from the lights to be absorbed effectively negating interference.
Option: Because fluorescent lights only affect an RFID system in close proximity, the lighting could be moved or replaced with LED or incandescent lighting (if possible).
Option: Set up the system with extra hardware to ensure that the necessary RF energy gets to the tagged objects. RFID Power Mappers are a great tool for measuring UHF RF energy in any given area and determining if enough energy is reaching the designated read zone.

What's the Problem with RF Waves and RFID?

Additional RF waves from other RFID systems can cause reflection and null zones which can mean that your RFID tagged objects are not read in specific places.

How do you Deal with Additional RF Waves in the RF Application Environment?

Other RFID applications or machinery that emit electromagnetic waves can create additional RF waves in the environment that create null zones and difficulty reading RFID tags.

Option: RF shielding or absorbing material like carbon-loaded foam can be used to separate the waves from the two systems so that there is little to no interference. To find out if there are existing UHF electromagnetic waves in the application environment, try using an RF Power Mapper that detects RF energy and then map out where exactly it is. Then shielding can be installed to keep the waves from interfering with the RFID system.

Conclusion

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