RFID Journal Staff asked 5 years ago Can I be sure that the meter will give me an accurate reading?
—Mohammed
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Mohammed,
To answer your question, I reached out to Dave Mapleston, the founder of ePix and the inventor of the Power Mapper. Here is his answer:
"To do accurate measurements of RF power requires a test house chamber; these chambers absorb radio waves so they don't reflect back and cause constructive or destructive interference. Any reflection from walls, metal objects and water will cause any meter to give results which could vary by 20 percent. So it's not the accuracy of the meter you need to be concerned about. It's the environment that causes errors in the results.
We have calibrated the Power Mapper at 1 meter with the -7 dB switch on. One meter is ideal, as it is far enough away to allow polarization to form and for the magnetic energy to dissipate, yet close enough to reduce the effects of reflections. With your reader set to 2W ERP in Europe or 4W EiRP in the U.S., the Power Mapper should read approximately 100 percent in an open environment. This can also depend on the calibration of the reader to account for circular polarization (-3dB).
In summary, no meter will give you an accurate reading unless used in a test house chamber; so for accreditation. you will still need to use a test house. However, for installation and comparisons of power outputs, and finding the areas of constructive or destructive interference, there is no better instrument than the Power Mapper."
—Mark Roberti, Founder and Editor, RFID Journal
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