If the master does not have RS485 communication port, a converter has to be
used. Normally a RS232/RS485 or USB/RS485 is adopted. The topology of RS485
net can be line, circle and star.
1. Line
The connection from master to Ai205 meter is one by one in the RS485 net as
in fig. 2.32.
In fig. 2.32 the Rt is a anti signal reflecting resistor 120-300 Ohm/0.25W.
Normally, it added to the circuit beside the last Ai205 meter, if the communication
quality is not good.
2. Circle
Ai205 meters are connected in a closed circle for the purpose of high
reliability. There is no need of anti signal reflecting resistor.
27
Fig 2.32 Line mode
Fig 2.33 Circle mode
Converter
Resistor
Master
PC
232/485
Converter
Master
PC
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