EMA11 - USER MANUAL
-26-
8.4) 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
EMA11
DCD
Data Carrier Detect
1
8
RX Receive
Data
2
3
2
TX Transmit
Data
3
2
1
DTR Data
Terminal
Ready
4
20
GND Signal
Ground
5
7
3
DSR Data
Set
Ready
6
6
RTS
Request To Send
7
4
CTS Clear
To
Send
8
5
RI Ring
Indicator
9
22
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.
8.4.1) 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 11
EMA 11
RS232/RS485
converter
COM
RX
TX
TX
RX
Rt
Max 32 EMA; max 1200 mt
Rt
COM
Summary of Contents for EMA11
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