My company grows Kumamoto oysters in floating bags, and would like to control individual bags with RFID tags. What types of tags could I use that would be waterproof 24/7 in salt water? The tags would not normally be immersed, but would always be at least wet, and they would need to be attachable to the PVC plastic pipe that we utilize to make floats. We would like to be able to read tags on a walk-by basis, or at a distance of up to 1,000 feet, if possible. What type of reader would best suit my needs?
—John (Oysterville, Wash.)
The easiest way to do this would be to use passive ultrahigh-frequency (UHF) RFID tags and a handheld reader. You would not achieve a read range of 1,000 feet, but it would be a simple solution to deploy.
With a handheld interrogator, you would be able to walk by the bags and capture their ID numbers. Motorola's MC9090-G and MC3090-Z models have what the firm calls a "Geiger Counter function," enabling the units to beep louder as a user gets closer to a tagged object being searched for. There are other handheld products on the market that could also do the job, including the CS101, from Convergence Systems Ltd. (CSL), and Intermec's IP30 with CK61 and CN3.
Using an active solution would allow you to read tags at longer range, but the tags would be more expensive, and you would need to install multiple readers around the oyster farm in order to locate the oyster bags in real time.
As for tags, Confidex offers several waterproof models that should work for this application. I suggest testing both the Carrier and Carrier-Pro models, both of which come with adhesive backing that would provide an excellent bond to PVC. Invengo also produces waterproof tags; specifically, the company's Hang Tag XCTF-8606 and Hang Tag XCTF-8113-C02 could be affixed to PVC.
—Mark Roberti, Founder and Editor, RFID Journal
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