Influence Of Metals - Siemens SIMATIC RF600 Series System Manual

RF600 system planning
4.5 The response of electromagnetic waves in the UHF band
Reducing the effect of reflections/interference on transponder identification
● Reducing the transmit power:
To minimize interference, we recommend that the transmit power of the reader is reduced
until it is sufficient for an identification rate of 100%.
● Increasing the number of antennas:
More antennas (3 or 4) in a suitable antenna configuration can prevent gaps in reader
coverage.
4.5.2

Influence of metals

Metal can have an effect on the electromagnetic field depending on the arrangement or
environment. The effect ranges from a hardly determinable influence through to total
blocking of communication. The term metal in this context also includes metallized materials
that are either coated with metal or shot through with metal to such an extent that UHF
radiation cannot penetrate or only to a minimal extent.
The effect of metal on the electromagnetic field can be prevented as follows:
● Do not mount transponders on metal.
The on-metal transponders designed specifically for use in metallic environments are an
exception to this.
● Do not place metallic or conducting objects in the propagation field of the antenna and
transponder.
Influence of metal on transponders
Normally transponders must not be mounted directly on metallic surfaces. The transponders
designed specifically for use in metallic environments are an exception to this (e.g.: RF690L,
RF620T, RF625T, RF630T, RF640T, RF680T).
Due to the nature of the electromagnetic field, a minimum distance must be maintained
between the transponder antenna and conductive materials. For more detailed information
on the special case of attaching transponders to electrically conducting materials, refer to the
relevant transponder sections.
In the case of transponders that are not designed for mounting on metallic materials, the
minimum permissible distance from metal is 5 cm. The larger the distance between the
transponder and the metallic surface, the better the function of the transponder.
Influence of metal on antennas
Note that metal surfaces located directly in the antenna field reflect the transmitted power
directly to the antenna. Due to the nature of the electromagnetic field, a minimum distance
must be maintained between the antenna and conductive materials. You can find more
detailed information on this in section "Specified minimum and maximum spacing of
antennas (Page 46)".
If the reflected energy becomes too strong in the receive path of the reader, this activates a
protective circuit that shows itself as an antenna error without there actually being an error in
the configuration or a defect on the antenna.
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System Manual, 11/2018, J31069-D0171-U001-A21-7618
SIMATIC RF600