NHA2768503-07

RS-485 wiring

Connect the devices on the RS-485 bus in a point-to-point configuration, with the (+) and (-) terminals from one device connected to the corresponding (+) and (-) terminals on the next device.
NOTE:

Straight-line topology only. Loop or ring topology is not supported.

Resistor is an optional accessory that you can order separately. To terminate a series, it is recommended to use a 120 Ω / 0.5 W resistor.

RS-485 cable

Use a shielded 2 wires or 1 twisted pair RS-485 cable to wire the devices. Use the twisted pair to connect the (+) and (-) terminals.

RS-485 terminals

C Common. This provides the voltage reference (zero volts) for the data plus and data minus signals
Shield. Connect the bare wire to this terminal to help suppress signal noise that may be present. Ground the shield wiring at one end only (either at the master or the last slave device, but not both.
- Data minus. This transmits/receives the inverting data signals.
+ Data plus. This transmits/receives the non-inverting data signals.
NOTE: If some devices in your RS-485 network do not have the C terminal, use the bare wire in the RS-485 cable to connect the C terminal from the meter to the shield terminal on the devices that do not have the C terminal.

RS-485 maximum cable length

The total distance for devices connected on an RS-485 bus should not exceed 900 m (2953 ft).

RS-485 network configuration

After you have wired the RS-485 port and powered up the meter, you must configure the serial communications port in order to communicate with the meter. Each device on the same RS-485 communications bus must have a unique address and all connected devices must be set to the same protocol, baud rate, and parity (data format).

NOTE: To communicate with the meter using ION Setup, you must set the serial site and all connected devices in the RS-485 network to the same parity setting.

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