Baumer Ident OIS-P PC 3100 series, Руководство по установке

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20 Baumer Ident OIS-P, PC3141/03 Manual
3.2 Metallic objects
Microwaves at 2.45 GHz have an excellent
capability of penetrating through foreign
substances, as described in section 3.3. However,
like all electromagnetic waves, microwaves cannot
penetrate through metallic objects.
Therefore, installations should be planned in such a
way that metallic objects are not present between
antenna and Data Tag when communication with
an Data Tag is to take place. However, small
metallic objects like metal shavings etc will not
influence negatively on the communication.
Further, both Antenna and Data Tags can be
mounted directly onto metal surfaces.
Any system operating in the MHz range or higher,
will have a communication range in which the
signal strength varies, due to wave reflections.
To minimize this phenomenon, the PC3100 system
features circular polarization, which suppresses
microwaves reflected from metal surfaces an odd
number of times. The suppression is equivalent to
6 dB or more.
To avoid the risk of negative interference from
metal surfaces, one of the following situations
should be established.
Environmental influence
A. Communication with the Data Tag is
performed in motion.
Any negative influence of reflections will result in
a slightly longer communication time. This
should be added to the communication time with
a margin dependent on the actual case, normally
a factor 2 (See section 2.1).
B. Communication is performed with the Data
Tag at standstill .
Metal surfaces in positions where they could
reflect microwaves from the antenna towards
the Data Tag should be studied. Generally they
should be at a position equivalent to a 6 dB
lower signal strength than the Data Tag, to
avoid negative influence. This can usually be
achieved by reducing the distance between
antenna and Data Tag.
Depending on reflections there may be points with
stronger or weaker signals and the position of the
antenna and/or the Data Tag should then be
adjusted to achieve a strong signal. The distance
between points with strong signal is normally 12.4
cm.