16
●
Problems in practical use
In some circumstances user adopts a star configuration in practical connection. The termination
resistors must be connected to the two equipments that are father away from each other, such as
equipment1# and 15# (refer to picture 4-1.3). As the star configuration is not in conformity with the
requirements of RS485 standards, problems such as signal reflections, lower anti-interference
performance arise when the cables are long in the connection. The reliability of control signals are
decreased with the phenomena that the dome dose not responds to or just responds at intervals to the
controller, or dose continuous operation without stop.
In such circumstances the factory will recommends the usage of Rs485 distributor. The distributor
can change the star configuration connection to the mode of connection stipulated in the
RS485standards. The new connection achieves reliable data transmission (refer to picture 4-1.4)
1#
6#
Master equipment 32#
15#
Fighure 4-1.3
Figure 4-1.4
120
Ω
120
Ω
2#
B-
120
Ω
120
Ω
120
Ω
A+
1#
3#
.
.
.
