Simultaneous RFID Tag Reader Hookup Guide

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Contributors: Nate
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Example 10 - Range Test

The PCB antenna on the shield will allow you to read tags up to around 24 inches at max read power (27dBm). If you really want to push the limit of read range you’ll need an external antenna. With a good external antenna we’ve seen read distances of up to 16 feet (4.5 meters)!

Keep in Mind: Ensure that personnel do not stand in the radiation beam of the antenna unless they are more than 21cm away from the face of the antenna (to adhere to FCC limits for long-term exposure). See Datasheet for more information.

Load Example10-Range Test onto your Arduino. As you bring a tag into range of the antenna you should hear a high pitched beep. When a tag is no longer detected you should hear a low pitched beep.

We are able to get more than 16 feet (4.5m) using the external antenna, with an external power supply (LiPo 1Ah battery), using SparkFun interface cables, and the URA software with the output power set to 27dBm. We didn’t heat sink the module but it quickly approached 60C as we were testing over the course of 5 minutes.

UHF Passive RFID range test

Large 7MB image showing distance from reader to tag

This is a large image but if you open the image in a new tab and look closely you’ll see the passive RFID tag hanging off the jaw of the T-Rex. Each carpet square is 2 feet and we were able to constantly read the tag more than 16 feet away! The NANO M6E is truly amazing.

But I’m not getting 16 feet!?

16 feet is really the best, most ideal situation. Our demonstration has no metal, no water, the tag is aligned with the antenna over open air and the power supply is as clean and powerful as possible (battery at 27dBm). Your real world results will vary greatly depending on many factors. It’s best to get the hardware and test in the environment your application will be within.

Check out our troubleshooting recommendations for RFID systems here.

Tag Location

Can I tell where a tag is located? Can I use UHF RFID for location within a room?

The short answer is no. The reader emits a ‘bubble’ of energy and any tag within that bubble will be energized and report itself to the reader. You’ll know if a tag is in the bubble but you won’t be able to tell where it is within the bubble. If your reader is capable of reading tags from 16 feet away, that’s amazing, but that means you won’t know if the tag is 1 foot or 10 feet from the reader. There is a caveat: the reader reports the RSSI (basically signal strength) for each tag. This means you’ll be able to tell qualitatively which tag is closer to the reader (tag 1 has a stronger signal so it’s roughly closer to the read than tag 2) but you won’t be able to tell quantitatively (you cannot tell if tag 1 is 1.5 feet or 2 feet from the reader).