EMM-5
instruction manual
IM441-EU-F v0.4
pag. 13
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.
RS485 /23 2 con vert er
Max 32 EMM; max 300 meters
R=120
:
]
]
CONNECTION WITH NOT SHIELDED CABLE
RS485/ 232 converter
Max 32 EMM; max 1200 meters
R=120
:
serial converter
]
]
RS232
RS485
CONNECTION WITH SHIELDED CABLE
www.fanox.com
Tel: 0034 94 471 14 09
Fax: 0034 94 471 05 92
Pag 13