RS-485 Connections ION 8000 Series User Guide
Page 78 Chapter 6 - Communications
External Modem Connections
NOTE
Optical isolation voltage is 750 V peak for 10 seconds at 62 Hz. There is optical isolation from all other
inputs and outputs except COM1 (RS-485 port).
RS-485 Connections
Refer to the ION 8000 Series Installation Guide for the RS-485 specifications.
If you have not installed the I/O Expander or the communications break-out cable,
a custom cable is required to connect the D+ and D- pins from the male Molex
connector to the RS-485 data bus. The I/O Expander box is wired as a DTE device
and does require a NULL modem cable/adapter to connect to the serial port.
NOTE
Optical isolation is from all other inputs and outputs (the COM1, RS-485 port is not isolated from the
COM1, RS-232 port). Isolation voltage is 750 V peak for 10 seconds at 60 Hz.
The break-out cable’s twisted pair provide connections for both of the meter’s RS-
485 serial communications ports. The first set is for COM1 RS-485 connections. The
second set is for either COM2 or COM4 RS-485 communications, depending on the
options ordered for your meter.
NOTE
The second RS-485 twisted pair connection is either COM2 or COM4 or inactive. The following points
determine their status, however check the communications LEDs on the side of your meter to see which
options are on the meter: If the meter has an optional COM4 port on the meter, then the RS-485 twisted
pair is COM4. If the meter has an internal modem (and no COM4), the pair is inactive. Otherwise, the
pair is COM2.
Up to 32 devices can be connected on a single RS-485 bus. Use a good quality
shielded twisted pair cable for each RS-485 bus, AWG 22 (0.33 mm
2
) or larger. The
overall length of the RS-485 cable connecting all devices cannot exceed 4000 feet
(1219 m). The RS-485 bus may be configured in straight-line or loop topologies.
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