In over 12 years of operation in the field of RFID technology, we have helped our customers solve many problems, and below are the 7 most common reasons for RFID chips or readers to not work properly. If you need professional advice, we are available at info@rfidspecialist.eu.
 
1. Metallic materials are interfering with the operation of the RFID reader or RFID/NFC chip

If the RFID reader is attached to a metal housing or if it lies on a metallic base, the reading distance between the reader and a tag can be reduced due to electromagnetic interferences. The solution is to raise the reader a few millimeters away from the metal base using an additional wooden or plastic layer, or you may use the very thin protective layers made from ferromagnetic materials. These layers are used inside electronic devices as smart phones, etc. and are called ‘EMI shielding material.’ One of such materials is 3M™ Flux Field Directional Material.

Just as the metal base interferes with the operation of the reader, it also interferes with the operation of the chip. If a chip is applied on a metallic surface and does not contain a protective layer, the metal reduces the radio frequency signals and the chip does not respond. The solution is to use transponders with special protection from ferromagnetic materials known as on-metal or anti-metal protection. It should be noted that sometimes, despite the use of transponders with on-metal protection, the operation of the reader is not completely normal, because the metal also affects the reader and weakens the signal. 


2. The chips are not compatible with the reader even though they operate at the same frequency

The operating frequency of the chips and the reader is not a guarantee that the reader will work with certain kinds of chips. To be sure that the both are compatible, it is necessary to check the communication protocols as well. The most popular HF readers that operate on the frequency 13.56 MHz are compatible to ISO/IEC14443 standards and don’t work with 13.56 MHz chips ICODE® SLIX that are compatible with ISO/IEC 15693. 

Another good example, is that the Mifare Classic® chips, which are operating at the same frequency as NFC chips, are not compatible with NFC standards. Some NFC devices may read the ID code anyway, but they cannot operate with a chip’s memory.

Even the 125 kHz readers do not read all 125 kHz transponders. If you buy a transponder with a 125 kHz T5577 chip the reader won’t read it because it has to be encoded first. The 125 kHz chips EM4550 are read-write chips and they won’t work with standard read-only readers.


3. The same RFID reader model can read the same RFID chip differently

Buying the exact same model of reader as the ones you have in your system does not guarantee that they will work the same because they can be set up differently. On some readers, (like the 125kHz reader Syris RD200-LF or 13.56 MHz reader Syris RD200-M1) you can setup the chip ID code reading format and other properties in more than 50 ways, while other readers can have a custom setup done during a manufacturing process. Before adding new devices to an existing system, it is recommended to test if the new equipment works the same as the existing. You can do this by reading the chip ID with a new reader (in a Notepad) and compare it to the ID code provided by the existing reader.

4. NFC readers usually do not read all types of NFC chips

NFC technology is a subset of RFID technology and is defined by NFC standards. There are five types of NFC transponders and they have their own specifics. To read the desired type of transponders, the reader must support the specific protocols.

- NFC Type 1: ISO/IEC 14443-3A protocol, Broadcom Topaz chips
- NFC Type 2: ISO/IEC 14443-3A protocol, NTAG213, NTAG215, NTAG216, Ultralight . . .  chips,
- NFC Type 3: JIS 6319-4 protocol, Sony FeliCa chip
- NFC Type 4: ISO/IEC 14443-4 A/B protocol (NXP DESFire chip, ST Microelectronics M24SR),
- NFC Type 5: ISO/IEC 15693 protocol, NXP ICODE SLIX chips, Texas Instruments Tag-It, EM423x, ST Microelectronics ST25DV
   
The inexpensive keyboard emulating 13.56 MHz RFID readers are not suitable for reading NFC chips because they usually read only 4-bytes of the chip’s ID code (8-digit HEX number), and the NFC chips have a 7-byte UID (14-digit HEX number). Such a reader only reads a part of the ID code, and it may happen that you get the same reading even for different chips.

There is another reason why the fully combatable NFC reader cannot read the NFC tag and this is that sometimes NFC tags contain very small antennas that can be read only if you buy specialized equipment.

5. Something can be wrong with a USB cable

Although seemingly all USB cables are the same, there are some USB cables that serve only for charging and do not have wires for data transfer. When using such a cable, the reader will not work. It is always recommended to use the cable which comes with the reader and this usually solves the problem. We also had a special case where the problems were caused by electromagnetic interference, as low-cost readers do not have shielded USB cables and are therefore are not resistant against electromagnetic interference. 

6. The chips or readers are locked by the solution provider

Some solution providers increase the security of their solutions by using locked RFID transponders that cannot be read with standard readers. They can use specially designed readers as well. In this case, you cannot use the standard components and you must purchase them from solution providers or authorized dealers.

7. The media or reader is not of adequate quality

We have had several instances of customers who have purchased RFID media or readers through eBay, Alibaba, and other online stores at attractively low prices and have encountered unexpected problems. Seemingly identical RFID cards, key fobs, and other transponders may differ in the quality and size of the antenna, the quality of the chip, the quality of workmanship, causing a very short reading distance or having a short lifetime.
Such white RFID cards do not necessarily have a special layer that allows a thermal print and such cards cannot be printed.

The renowned proximity reader manufacturer Advanced Card Systems Ltd. issued a declaration against counterfeit ACR122U NFC readers which are available on such online stores and sold at uncompetitive prices. These readers have only the appearance of the case in common with the original, but the electronics and firmware are completely different.