Do Any Companies Make Handheld Units That Can Read RFID and Measure Distance?

By RFID Journal

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Ask The ExpertsDo Any Companies Make Handheld Units That Can Read RFID and Measure Distance?
RFID Journal Staff asked 8 years ago

Can we identify silos, measure the height of grain and then download that information to a network using Wi-Fi or a docking station?

—Name withheld


The answer to your question is, essentially, no. Handheld readers measure received signal strength, which allows them to beep louder as they get closer to a tag, or to provide other indications of proximity to a tag. However, the received signal strength indicator (RSSI) does not correlate precisely to distance. This is because there are many factors that can influence signal strength, such as whether metal is reflecting the signal back to the handheld device, or whether heavy moisture in the air is attenuating the signal slightly.

Given that your environment is likely fairly static (I presume that not much changes besides humidity levels), it might be possible to mount an overhead reader at the top of the silo and then place a tag that floats at the top of the grain, moving up or down as grain is added or removed. The fixed reader could probably be calibrated to measure RSSI more precisely than the handheld and, in a controlled environment, could give you a pretty good sense of how much grain remains in the silo at any given time. Since each interrogator has its own unique ID number, you would know which unit is reporting on which silo. We recently published a premium-content article that you might find interesting—see What You Need to Know About Overhead RFID Readers.

—Mark Roberti, Founder and Editor, RFID Journal

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