Pepperl+Fuchs Blog

Frequently Asked Questions on RFID (Part 2)

Posted by Klaus Schmitt on Fri, Feb 19, 2016

General questions about RFID readers

1. What is an RFID reader?

An RFID reader is an active device that uses radio frequency to read information contactless from a data carrier like an RFID tag. Most of the readers are also able to function as write units. Typically, RFID reading devices contain a microprocessor or digital signal processor.

Industrial RFID Questions Part 2 RFID ReadersAn RFID reader is equipped with an internal or external antenna that grabs the information from the RFID tags. The data is then passed on by the reader to a communication unit that transmits the information via interfaces (PROFIBUS, MODBUS, PROFINET, Ethernet, Serial, and many more …) to an external host system which allows the interpretation of mass data or the targeted search for certain tagged pieces. These can include warehouse management systems, production planning systems, or ERP systems.

2. What are the most common types of RFID readers?

RFID readers don’t come in standardized forms or shapes, but are available for a variety of industries and different applications. Thus, there are several different criteria to cluster them: range, frequency, protocol types, power … the main distinction that can be made between them is in regards to stationary and mobile RFID readers.

For industrial applications, stationary readers are permanently mounted at relevant positions in a plant or factory. In access control applications, a stationary RFID reader is, for instance, mounted next to a security door and waits for workers to identify themselves with their personal RFID tag. In both cases, the RFID reader communicates directly with an external host system.

Mobile RFID readers (also known as RFID handhelds) offer similar functionalities but feature a more compact, cell phone-like design and do not require a power connection. Data is stored temporarily on the mobile readers and then submitted to a host system later on. This happens either via Wi-Fi or by plugging the mobile RFID reader into a docking station. For instance, at a loading dock, a mobile RFID reader is a great tool for workers to quickly identify packed goods on a pallet.

3. What is reader collision and how to deal with it?

The term “reader collision” refers to possible cross-talk between RFID readers that are mounted in proximity to one another. This is an issue that especially earlier UHF read/write heads suffered from. Today, this is not much of a challenge anymore: modern UHF RFID read/write heads, like the ones we manufacture, are equipped with so-called “frequency hopping algorithms” or “dense reader mode.” This operation mode prevents UHF RFID readers from interfering with one another. Readers use a certain frequency range and switch channels on that frequency range often. Another more conservative and more expensive approach is to use shielding for the readers.

4. How does antenna polarization affect the performance of UHF RFID readers?

The polarization of radio waves that a UHF RFID reader sends out is critical to the reliable identification of objects. There are three major polarization types: linear vertical, linear horizontal, and circular. For linear vertical and linear horizontal polarization, the direction of the vector transmitted from the electromagnetic field component remains constant in space. Other RFID readers use a circular polarization where electromagnetic fields are emitted in a corkscrew-like fashion. To achieve a UHF system’s maximum detection range, the read/write head’s polarization must match the tag’s polarization. RFID tag antennas are typically linear polarized. Simply speaking, linear polarized antennas tend to have a greater read range than circular polarized antennas with the same gain when polarization matching can be achieved by proper alignment. On the other hand, circular polarized antennas fare better when it comes to reading tags of varying orientation.

The latest RFID readers, like our F190 and F192 RFID UHF read/write heads, make use of different polarization types to achieve the most reliable identification results: In applications where tag orientation is steady or known, simple linear polarization gets the job done. You can fine-tune the adjustment of the antenna polarization to the tag, reduce the power level, and you are good to go. But when orientation of the RFID tag is unknown or may vary, you can also run these advanced RFID readers in automatic switching mode. Using this combined approach of vertical and horizontal linear polarization, reliable detection becomes independent of tag orientation. This is very useful when it comes to identifying unsorted cargo.

5. Which reader should I choose?

Picking the right reader for your application depends on several considerations. As mentioned before, antenna polarization is one factor that weighs in. But of course there are other things that you want to pay attention to: Confined installation spaces in factories or plants demand extremely compact readers.

  • Which housing designs does your supplier provide?
  • How about the durability of the reader?
  • Will it be used in washdown areas or exposed to high temperatures?
  • Will your identification solution be rolled out on a global basis?

Here you benefit when one supplier can provide the same exact RFID reader for different regional frequency ranges.

You might also enjoy:
Frequently Asked Questions on RFID (Part 1)
Frequently Asked Questions on RFID (Part 3)
Frequently Asked Questions on RFID (Part 4)

Questions about Industrial RFID?  Ask an Expert!

Topics: RFID

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