Configuring with the WBM
7.3 The menu items of the WBM
SIMATIC RF650R/RF680R/RF685R
Configuration Manual, 03/2018, C79000-G8976-C386-06
57
Parameter
Description
RSSI threshold
The RSSI threshold specifies the signal strength above which a transponder is
identified. Only the transponders that reach the RSSI threshold are entered in
the list of identified transponders.
In reflecting environments (metal reflects UHF waves), transponders could be
detected that are not located directly in the antenna field and therefore should
not actually be "read". The RSSI value of these transponders is usually no-
ticeably lower than the RSSI value of transponders located directly in antenna
field. Such transponders can be filtered out with a suitable RSSI threshold
value.
In the "Diagnostics - Tag monitor" menu item, all the detected transponders
are displayed along with their RSSI values. From the RSSI values of the tran-
sponders that should be read and the RSSI values of the transponders that
should not be read, it is possible to derive an RSSI threshold value.
Value range
0 ... 255
Increment
1
Input attenuation
The input attenuation weakens the strength of received transponder signals at
the reader input. Increasing the attenuation means that received weak tran-
sponder signals are no longer identified by the reader. This attenuation applies
both to transponder responses as well as to signals of neighboring readers.
Adapting this parameter helps to reduce disruptions caused by neighboring
readers and transponder populations.
Value range
0 ... 31.75 dB
Increment
0.25 dB
Polarization
The polarization indicates the alignment of the waves of the antenna and de-
pends on the antenna being used. Most antennas have an unchangeable
polarization.
The polarization of the internal antenna of the RF685R reader can be set - just
like the RF680A antenna. If you use the internal antenna of the RF685R read-
er, you also need to enable the required polarization using the corresponding
check box. If more than one check box is selected, the polarization is changed
with each inventory. This increases the probability of identification in difficult
radio conditions but does, however, increase the access time (time required
for the additional inventories).
Algorithms
Compared with other frequency bands (LF, HF), UHF RFID has the following special
properties:
●
Large distances in the range of several meters,
●
Reflection of the waves on metal surfaces,
●
Region-dependent bandwidth restricted by regulations
In conjunction with the fact that electromagnetic waves in the UHF range are not visible, this
often leads to unwanted or incomprehensible responses in UHF systems. Typical, simple
examples include:
●
Not everything is read or even nothing is read.
●
Reading works but writing does not.
●
Transponders are identified that should not be identified at all.
