Nexus 1250 - 2: Remote Communication-RS485; 3: Programming Modems for Remote Communication

Doc# E107706 5 - 15
5: Communication Wiring
Electro Industries/GaugeTech
The Leader In Power Monitoring and Smart Grid Solutions
Electro Industries/GaugeTech
The Leader In Power Monitoring and Smart Grid Solutions
NOTE: Connecting the Nexus® meter to a modem via RS485 protocol with EIG’s
Modem Manager converter eliminates the need for a Null Modem (see Section 5.8.2).
• The remote modem must be programmed for auto-answer and set at a fixed baud
rate of 9600 with no Flow Control. See Section 5.8.3 and the Communicator EXT
TM
4.0 and MeterManager EXT Software User Manual for further details.
5.8.2: Remote Communication-RS485
Use any Port on the Nexus® 1250/1252 meter. If you use Port 1, set the selector
switch beneath the port to RS485. The link using RS485 is viable for up to 4000 feet
(1219 meters).
Use Communicator EXT
TM
software to set the port's baud rate to 9600 and enable
Modbus ASCII protocol. See Chapter 13 in the Communicator EXT
TM
4.0 and Meter-
Manager EXT Software User Manual for instructions. Remember, Modbus RTU will not
function properly with modem communication. You must change the protocol to
Modbus ASCII.
You must use an RS485 to RS232 converter and a Null Modem. EIG recommends
using its Modem Manager, a sophisticated RS232/RS485 converter that enables
devices with different baud rates to communicate. It also eliminates the need for a
Null modem 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.
5.8.3: Programming Modems for Remote Communication
You must program a modem before it can communicate properly with most RS485 or
RS232-based devices. This task is often quite complicated because modems can be
unpredictable when communicating with remote devices.
If you are not using the EIG Modem Manager device, you must set the following
strings to communicate with the remote Nexus® meter(s). Consult your modem’s
manual for the proper string settings or see Section 5.8.3.1 for a list of selected
modem strings.
NOTE: Use a Modem Manager! The product was designed to make this task “plug and
play.” We highly recommend it for all serial modem solutions.