Contrel EMA-D9, Руководство пользователя

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EMA-D9 - USER MANUAL
-23-
7.4) SERIAL OUTPUTS
Through the combination of an asynchronous serial RS485 and RS232 communication line it is
possible to exchange information between the instrument and PC, PLC or other compatible systems.
All transmitted characters are in ASCII (American Standard Code for Information Interchange) format.
RS485 allows a multi-drop connection, in order to link-up several instruments on the same network, on
the other hand RS232 allows a single point connection. This last connection must be carried out when
both systems are turned off and disconnected from the power line, in order to avoid damages on the
serial output. RS232 may be 9 or 25 pin connection, please follow up the enclosed table:
Signal Description DB9 DB25 EMA-D9
DCD Data Carrier Detect 1 8
RX Receive Data 2 3 38
TX Transmit Data 3 2 37
DTR Data Terminal Ready 4 20
GND Signal GrouND 5 7 39
DSR Data Set Ready 6 6
RTS Request To Send 7 4
CTS Clear To Send 8 5
RI Ring Indicator 9 22
Warning: to communicate with a PC, use only one of the 2 standard serial outputs.
The maximum suggested length of a RS 485 connection is about 1200 mt., while for a RS232
connection about 5 mt.
For longer distances, cables with low attenuation, or connection to line amplifier are recommended.
Up to maximum 32 units can be wired on the same serial line (RS485), exceeding this number it is
imperative to insert a signal repeater, each repeater can manage up to 32 instruments.
The polling time is directly proportional to the instruments number connected on the same serial line.
7.4.1) RS485 CONNECTION NOT SHIELDED
Once a RS485 network has been configured; to communicate between the Host (computer) and the
instrument(s) (EMA) a serial interface converter must be wired between PC and instrument(s) as
mentioned on the above picture. In serial line over 500 mt, connect a line termination resistor
(Rt=100
Ω
- 120
Ω
) between the two twisted pair cables leading from the converter at the end of the
network (last connected instrument). It’s recommended to use always twisted pair cable with minimum
cross-section of 0.36mm
2
(22AWG) and capacity less than 60 pF/m (i.e. BELDEN cable type EIA
RS485-Ref.3105A).
EMA-D9 EMA-D9
RS232/RS485
converter
A A B B
Rt
Max 32 EMA; max 1200 mt
Rt
B1 B1 A1 A1
RS485(1)
RS485(1)
Rx Rx Com Com
RS232
RS232
Tx Tx
!