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Doc # E107706 V1.25 5-21
5.17:
Remote
Communication—RS-2232
EIG recommends using RS-485 wiring with a Modem Manager. See section 5.13.
For RS-232 communication, use Port 1. Set the selector switch under the port to RS-232 (Fig. 5.3).
Use an RS-232 serial extension cable connected to the 9-pin female serial port of the Nexus
1250/1252 Meter’s Port 1. Program this port for Modbus ASCII. See the Communicator EXT User
Manual for details.
The link using RS-232 is capable for up to 50 feet (1219 meters).
You must use a Null Modem or Null Cable between the Nexus Meter and the remote modem when
using RS-232. A Null Modem enables two DCE devices to communicate. The figure below details
how a null modem reconfigures the RS-232 pins. Note: Connecting the Nexus Meter to a modem
via RS-485 protocol with EIG’s Modem Manager converter eliminates the need for a Null
Modem; see section 5.13.
The remote modem must be programmed for auto-answer and set at a fixed baud rate of 9600 with
no Flow Control. See section 5.19 and the Communicator EXT User Manual for further details.
1 6547
20
832
1
2 3 4 5 6 7 8
20
Pins at Null Modem Female End
Pins at Null Modem Male End
Figure 5.19: Standard Null Modem Configuration
5.18:
Remote
Communication—RS-4485
Use any Port on the Nexus 1250/1252. If you use Port 1, set the selector switch beneath the port to
RS-485 (see Figure 5.3). The link using RS-485 is viable for up to 4000 feet (1219 meters).
Use Communicator EXT software to set the port’s baud rate to 9600 and enable Modbus ASCII
protocol. See the Communicator EXT User Manual.
You must use an RS-485 to RS-232 converter and a NULL Modem. EIG recommends using its
Modem Manager, a sophisticated RS-232/RS-485 converter that enables devices with different
baud rates to communicate. It also eliminates the need for a NULL modem (see section 5.12), and
automatically programs the modem to the proper configuration. Also, if the telephone lines are poor,
Modem Manager acts as a line buffer, making the communication more reliable.