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galvanically disconnected. This feature helps to solve problems created by leaking
communication lines.
Repeaters may be needed in two cases:
1.
When the RS485 line gives poor results and the signal needs strengthening.
2.
When the system contains several 2 wired channels and we want to isolate each
channel from the others. In this case the first 2W interface, which is fed directly from
the DREAM does not require a repeater, but all the others will be fed separately and
will have their RS485 communication line isolated by repeaters.
In the second case, we want to eliminate crosstalk between the various two wired channels,
therefore we have to create galvanic isolation between them. There is a great importance to the
way the repeater board is energized by the 12v DC, the energizing has to be from the side of
the output where the 2W interface is connected and not from the side of the input, which
arrives from the DREAM. Otherwise, we shall loose the effect of isolation. For this purpose, the
repeater board has the ability to be powered either from the input side or from the output side
while the two sides remain galvanically isolated. For feeding from the output side, the 4
jumpers JP7, JP9, JP10, JP11 should be in right position (opposite to what appears in the
picture above).
The dipswitches in this case function as a baud rate selector with the following options:
1-2400
2-4800
3-9600
4-14400
5-19200
6-28400
In the peripheral RS485 communication channel of the DREAM system the baud rate used is
9600 baud, therefore the third option need to be selected.
9.2.2
2 or 4 Analog inputs interface
The jumper that decides the functionality of the board
for serveing as an analog inputs interface is jumper JP12
that should be set in left position as demonstrated in
the drawing to the right.
When the
REBRAN
board
is used as an analog inputs
interface,
it will be added a
plug in unit that contains the
terminals for the analog inputs
connection and the dipswitches
for selecting between 4-20 mA
and 0-5v sensors.
Input side
RS485
JP12 set for ANALOG
INTERFACE function
S1 - Address switch
S2 - selects between
4-20mA or 0-5v input