Siemens SIMATIC RF600 Series System Manual page 57

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.
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.
This effect depends very much on the transmitted power, the components being used (cable,
antenna) and the distance from the metallic surface to the antenna. In this case,
repositioning/realigning the antenna or reducing the radiated power can remedy the
situation.
SIMATIC RF600
System Manual, 10/2016, J31069-D0171-U001-A19-7618
4.5 The response of electromagnetic waves in the UHF band
RF600 system planning
57