Learn how to understand and compare RFID reader read ranges and select the readers that best fit your RFID system implementation.
If you’re or have previously been in the process of searching for UHF RFID systems in general, you probably have noticed that it is not easy to understand specifications, let alone compare them.
Even if there are other specs these systems work with (user data, sensors, data logging, etc.), RFID solutions are all about identification and read range.
Read Range is dependent on multiple variables
Comparing memory space available for example is very easy between tags. However, you will find some trouble when trying to understand how the read range of a tag compares to another one.
You will read about IC sensitivity, tag antenna gain, meters of read range or even output power of a reader. Once again, for simplicity, the key to understand is that there are three main parts in an RFID system that heavily impact the read range: RFID tag IC, RFID tag antenna and RFID reader.
These three different parts may use different words in their datasheet or commercial collateral to eventually address the read range you can obtain with them. Let’s go one by one:
‘Decoding’ rfid reader read range information
Readers will generally give their rfid reader read range specification as output power. It is a value in dBm, the higher value meaning more power being transmitted from the reader. Remember that there a country regulations limiting the output power from the reader (have a look at the GS1 regulations table as a reference).
However, you can also get the rfid reader read range as output power value in Watts. To make things simple, you shall take 30 dBm as 1W output power. From there, every 3 dBm higher the power doubles and every 3 dBm lower the power is just the half of the previous value.
ERP vs EIRP, what the hell is that and how can I compare them?
You will also notice that some readers will show Watt values as ERP while others share it as EIRP. This means that the output power is given including the gain of the reader antenna – you will usually find this in handheld readers and integrated readers, as both of them have an antenna of their own. Basically, EIRP thinks about using a completely isotropic antenna – isotropic antennas have a lower RF field intensity as the radiation pattern is wider.
You will notice that 4W EIRP and 2W ERP are very common values for readers. The reason behind that is country regulations – ETSI regulation (Europe) using 2W ERP and FCC regulation (USA) using 4W EIRP.
A post from Impinj about the ERP and EIRP power output is quite clear about it. As you can see, the FCC allows for a little bit more output power, which in turn allows the complete system to achieve slightly longer read ranges.
RFID reader read range in meters, beware!
Some reader manufacturers will just share a distance in meters as the reader performance. I personally find it very interesting as they are sharing the performance in exactly the terms you as a user are interested in.
However, it is not that easy. RFID system read range is also determined by the reader antenna being used and the tag being read. If you are able to do so, gather more information about what the conditions for those RFID reader read ranges are – meaning understanding what the total power output is and what tag they are using for the specification. Read ranges of 3 meters can be achieved both with a 20dBm output power and a very good tag and with a 33dBm output power and a very bad tag.
We will go deeper in decoding RFID system read ranges in the next post by addressing the RFID tag side. There too the information can be found in different ways and we will try to help you compare and select the best fits for your applications.