EMC INDUSTRIAL GROUP LTD Connections
MW61A_IM_ALL_SV6.09d_en 13/47
Multidrop Systems
ModWeigh instruments can be connected using the COM2 RS485 bus. Up to 10 systems may be con-
nected on the bus. A ModWeigh display can select any one of the systems on the bus to work with.
A multidrop connection can also be used with any other Modbus master device such as a PLC. If a non
ModWeigh master is used on the bus, then the ModWeigh instruments are unable to communicate with
one another. An external Modbus master can alternatively be connected to an RS232 COM1 port.
An MR1 unit cannot share the bus with a non ModWeigh master such as a PLC. A PLC could be con-
nected using the COM3 port on the MR1.
To connect in mutidrop use the RS485 connection COM2. The wiring should be made in a daisy-chain,
with one instrument connected to the next. If a stub connection is used to a main cable as shown in the
diagram, then make sure its length limit is adhered to.
Two MAT line terminators must be fitted, one at each end of the cable run.
The +D, -D and a 0V terminal must all be connected together through the data cable.
][
40
m
n
Li ≤
][500 mL
if D = MD1,MD2 Display, then n ≤ 10
if D = PLC master, then n ≤ 32
3
2
Allows corner adjustment and individual
monitoring of loadcell outputs
optional sense for 6 wire
connection
2
+E
+E
Loadcells Wired to Junction Box
For best accuracy use a 6-wire connec-
tion to controller
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