EMM-R4h EMM-
μ
4h
instruction manual
IM441-U v0.7
pag. 15
COMMUNICATION INTERFACE EIA485 (RS485)
It is possible to exchange information between the instrument and a PC, PLC or other compatible system, through the
asynchronous serial line RS485. The interface EIA485 allows a multi-drop connection, in order to connect various
instruments in the same network. The maximum suggested length for a RS485 connection is 1200m. For longer
distances provide the use of low attenuation cables or signal amplifiers. On the same RS485 it is possible to install up to
32 units, beyond this number of units it is required to place a signal repeater, each one of them will be able to manage up
to 32 instruments. The higher is the number of connected instruments on the same serial line, the lower will be their
response speed.
Not shielded connection
As shown in the diagram, it is necessary to place a serial
RS232/485 converter between the RS232 PC's outlet and
the instrument/s.
it’s necessary to insert a line termination resistance
(Rt=100÷120 ohm) between the twisted pair of cables,
placing it between the converter and the end of the network
(last instrument connected). Use always twisted cables with
minimum section of 0,36mm
2
(22AWG) and lower capacity
of 60 pF/m (i.e.: BELDEN cable type EIA RS485-
Ref.3105A).
Shielded connection
Should it be the case of long distance networks, ambiences
where there have been placed energy transporting cables or
ambiences subject to be electrically disturbed, it is
suggested to use 100÷120ohm 1/2W resistors, placed
between the common of the RS485 outlet and the shielded
cable.
For other information on the serial line it’s better to see the manual of EMI1 serial converter.
DIMENSIONS
R S48 5/2 32 con ve rte r
Max 32 EMM; max 300 meters
R=120
A1
B1
A2
B2
serial converter
C1
R1*
R2*
C2
LINE 1
LINE 2
]
]
RS232
RS485
CONNECTION WITH NOT SHIELDED CABLE
PERSONA
L COMPUT
ER
RS485/ 232 converter
PERSONA
L COMPU
TER
Max 32 EMM; max 1200 meters
R=120
A1
B1
A2
B2
serial converter
C1
R1*
R2*
C2
LINE 1
LINE 2
]
]
RS232
RS485
CONNECTION WITH SHIELDED CABLE
68
68
R3
72
72
cut panel
72
81
14
9
65
.8
EMM-µ4h
L
L1
L2
L3
electrical
multi meter
kWh
kVArh
...h
V
A
P.F.
W
VAr
VA
V
L-N
L-L
V
L-N
Hz °C
V
L-L
alarm
k
max
avg
maxD
max
avg
K
M
92
92
R3
96
96
90
96
56
9
20
cut panel
k
M
k
V
L-N
L1
L2
L3
L
Hz
electrical
multi meter
V
A
P.F.
W
VAr
VA
V
L-N
L-L
°C
V
L-L
alarm
kWh
kVArh
...h
max
avg
max
maxD
avg
EMM-R4h