Influence Of The Environment; Setting The Read And Capture Repetitions; Static And Dynamic Applications - Balluff BIS U-4A7-082-01C-07-S4 Betriebsanleitung

BIS U-4A7-082- _1C-07-S4
Industrial RFID system - Read/write head
5
Application planning (continued)
5.10

Influence of the environment

The environment in general has a strong influence on the
behavior of radio-based technical systems and can affect
functions of the RFID system.
The following measures can reduce negative effects:
– Set the transmitting power correctly (see chapter 5.8
on page 16)
– Keep the line of sight between the data carrier and the
read/write head as free as possible from conductive
objects and liquids
– Do not point the read/write heads against each other,
but point the main beam direction in different directions
– Change the position or orientation of the read/write
head (sometimes a few centimeters or degrees are
sufficient)
– Attach shields
Intra-system interference/external interference
The radio waves of a transmitting read/write head can be
reflected by metallic structures and scattered back so that
they are received again by the antenna. As a result, the
backscattered radio signal can overlay signals from data
carriers and interfere with reception. Radio signals from
one read/write head can also cause interference in the
receiver of another read/write head.
Destructive interference and over-coverage
Multipath propagation can occur due to reflections at
different metallic structures. In this case, the radio signal is
reflected at different metallic structures in different
directions, where it can then also be reflected again by
other metallic structures. Particularly when several read/
write heads are used simultaneously, this can result in a
complex interference field that causes local maxima and
minima.
Put simply, this means that places can arise where a data
carrier can be detected particularly well (over-coverage)
and places where this is less possible or not possible at all
(destructive interference).
Superimposition of radio signals from several read/
write heads
Due to reflections, radio signals from several readers that
have different detection ranges can overlap in such a way
that data carriers in one detection range receive signals
from several read/write heads simultaneously. Under
certain circumstances, this can lead to a disturbed,
superimposed signal arriving at the data carriers and data
carriers thus not being able to decode requests from the
read/write head.
5.11

Setting the read and capture repetitions

The Number of repetitions parameter can be used to set
the number of repetitions after an unsuccessful access
attempt to a data carrier or a capture request.
The setting has an influence on the duration of the
command processing. The higher the value of the
parameter setting, the longer the response time in the
event of an error.
18 english
The setting depends on the application:
– For dynamic and time-critical applications, a small
parameter value should be selected.
– In an environment with major electromagnetic
interference, a larger value can lead to better results.
5.12

Static and dynamic applications

In static applications, the objects to be detected are
brought to the detection area with the data carriers and
then remain stationary during the read/write process. Once
the process is complete, the objects are transported on to
the next station for the next process. In dynamic
applications, the objects continue to move during the read/
write process.
Static applications
In static applications, the phenomena described in
chapter 5.10 on page 18 may occur more frequently. If
these phenomena lead to problems, they can be
eliminated or reduced, as also described in chapter 5.10.
Dynamic applications
In dynamic applications, the environment plays a rather
subordinate role, since the objects to be identified move
and therefore pass locations with good and poor
reception. More important is the speed at which objects to
be identified pass through the detection area and therefore
how long these objects stay in the detection area. The
longer objects stay in the detection range, the more time
the desired read/write operation can take.
The section Access times for the detection of data carriers
on page 19 provides guidance on the time it takes to
detect data carriers.
By aligning the read/write head to the direction of
movement of the object, the duration of stay in the
detection area can be varied.
1 Short travel path in the limit area (should be avoided)
2
Normal travel path parallel to the read/write head
3 Long travel along the main beam direction
Fig. 5-13: Travel paths