How to Troubleshoot RFID System Errors

By Megan R. Nichols

When developing and implementing an RFID solution, it's a good idea to test early and often.

Radio frequency identification systems have become increasingly popular in recent years. These tags are now commonly used in a range of applications—like in employee badges or warehouse goods. However, RFID systems can often work improperly due to subtle design mistakes that can result in cascading or difficult-to-notice errors.

These issues can be challenging to troubleshoot, simply due to the number of things that can go wrong. Fortunately, it is possible to achieve a near-100 percent read rate on RFID tags, so long as you know common errors to look out for. Here are 10 different ways to troubleshoot an RFID system.

1. Review Material of Tagged Products
When troubleshooting an RFID system, review handbooks to ensure material type or density do not cause issues with signal transfer. Dense or water-laden materials can absorb radio waves, preventing unpowered tags from reflecting signals to RF readers. Metal can also cause detuning, which will prevent connections.

If you need to use an RFID tag on a metal object or a product that contains a large amount of liquid, consider using on-metal versions. You can also use battery-assisted passive tags, which can send a stronger signal on products containing liquid. When possible, ensure workers aren't holding tags when reading them and are not standing between a tag and reader. The human body is mostly water and can easily absorb an RF signal.

2. Check Tag Orientation
Some tags can be read regardless of their orientation. However, in some systems, if the reader and tag aren't well-aligned, it won't receive enough energy to return a signal. If a reader can't consistently read a tag, make sure they are aligned correctly when scanning.

3. Manage Reader-Antenna Cable Length
The longer the cable connecting an antenna and reader, the more energy will be lost. If it's too long, the reader may not even have enough power to send an adequate signal. If you're experiencing difficulties like this, ensure antenna cables aren't too long. When possible, try to minimize the distance between the reader and antennas.

4. Consider Tag Size
In general, small tags will have shorter read ranges. If you are struggling to read a particular RFID tag, consider upgrading to a larger tag size. For example, replace a button tag with a card tag.

5. Prevent RF Interference
When possible, test for and limit sources of interference that can degrade RF signals and prevent tags from being read altogether. Common sources of RF interference include dirty power in industrial settings, consumer devices like smartphones and electronics with design failures that are causing issues with electromagnetic compatibility.

6. Manage RFID Reader Density
RFID readers can crowd each other out, especially in applications for which the available RF spectrum is limited. This problem is most likely to occur in situations in which there are a large number of mobile RFID readers—such as in a retail environment or a warehouse that has integrated RFID into its bookkeeping or picking-and-packing process.

Interference or collision between RFID readers can cause signals to degrade, reducing performance to the point at which individual readers become temporarily unusable. Keep tabs on the number of RFID readers you have and the amount of RF spectrum that's available. If you have difficulty scanning tags, make sure you can rule out reader collision before moving on to other troubleshooting methods.

7. Manage Tag Density and Organization
Overlapping tags and those that are crowded together can prevent successful readings. Managing density and organization can help to avoid tag collision. Preventing tags from overlapping can also help you avoid issues like shadowing, in which multiple ones are lined up in front of each other. When this happens, only the first tag will absorb the reader's energy and return a signal.

8. Test New Tags in the Right Environment
Ambient RF interference and other issues can make it difficult to properly test tags in the environment where they are deployed. This is especially true if your facility is regularly adding in new technologies that may or may not contribute to RF interference. If you are uncertain whether or not a read rate issue is being caused by the tag or its environment, you can test it in an anechoic chamber designed for RF testing. This test can let you know how effective it is and determine things like tag read range.

9. Regularly Monitor Your RFID System
Start with the best possible data by periodically monitoring your RFID system. If you aren't doing so already, keep track of where tags and readers are located, and maintain records of read failures. Monitoring can help you better identify what may be causing issues, and it can also rule out common obstacles—like reader or tag overcrowding, or RF absorption caused by certain materials.

10. Perform Early Real-World Tests
Ideally, before an RFID system is taken live, you should test it in the environment in which it will be applied. This can help you catch common problems, such as material interference with RFID tags or other issues that may prevent it from being read. Mitigate or prevent them before the system is integrated into work processes.

Managing Common RFID System Errors
RFID systems can run into a range of common issues, especially in work environments containing significant levels of radio noise. When developing and implementing an RFID system, it's a good idea to test early and often. This will allow you to catch potential issues as soon as possible and give you the best idea about what may be causing read failures.

Megan R. Nichols is a STEM writer who contributes to sites like Sensors Online and EPS News. Megan has also published easy-to-understand manufacturing and engineering articles on her personal blog, Schooled By Science. Keep up with Megan by following her on Twitter.