MaxiProx optimum read range Continued
AN010f.doc
PAGE
Date: 1-28-
99
by Eric Sprik
Updated 5/21/01
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Switching power supplies can generate electrical “noise” that is radiated or
conducted. This inherent electrical noise can interfere with card data
transmission to the reader, reducing read range.
MaxiProx readers surround themselves with a radio frequency
excite field. This RF energy field provides power to HID
Proximity cards. The field is elliptical in shape and extends
about three feet in front of and behind the reader. The field also extends about
8” from the edges of the reader.
Metal of any type (aluminum, copper, lead…) should be avoided when
mounting a MaxiProx. Even non-ferrous metal within the field can affect reader
performance in two ways:
1. Metal absorbs the excite energy that is meant to power the card.
2. Metal de-tunes the reader’s antennas.
Reduced read range is the result. The degree to which the read range is
affected is dependent on how much and how close the metal is to the reader.
If metal is unavoidable, then absorption loss will be likely. But the de-tuning
effect can be somewhat compensated by re-tuning the reader. Some tips on
mounting and tuning are included later in this document.
Since all RFID (Radio Frequency Identification) readers are
radio frequency devices, care should be taken to avoid
Radio Frequency Interference (RFI) in the mounting area.
Some electronic equipment can generate RFI at a frequency that interferes
with the card data transmission to the reader. As an analogy, when a vacuum
cleaner is plugged into the same power line as a television, the TV’s
reception becomes very poor, but the picture quality returns to normal once
the vacuum is turned off. There is nothing wrong with the TV; the vacuum
motor generates “noise” (unwanted electrical frequencies) on the power line.
Some computer monitors, vehicle detect loops, and industrial equipment can
emit RFI that causes interference with the card data transmission to the
reader. Most equipment does not emit an interfering frequency. But it is best
to plan the placement of readers away from equipment that generates RFI.
MaxiProx readers can also interfere with each other, so they should not be
mounted closer than six feet back to back, or three feet side by side. Cross
reads can also occur. This will cause the card data to be transmitted by the
wrong reader.
METAL
RF NOISE
