For All Rs485 Connections - Eaton IQ 100 series User & Installation Manual

IQ 100 Series (130/140/150) Meter
Communication Installations
The figure below shows 2-wire RS485 connection in detail.

For All RS485 Connections:

• Use a shielded twisted pair cable 22 AWG (0.33 mm 2 ) or thicker, and ground the shield, preferably at
one location only.
• Establish point-to-point configurations for each device on a RS485 bus: connect (+) terminals to (+)
terminals; connect (-) terminals to (-) terminals.
• You may connect up to 31 meters on a single bus using RS485. Before assembling the bus, each
meter must have a unique address.
• Protect cables from sources of electrical noise.
• Avoid both "Star" and "Tee" connections (see figure on the next page).
• No more than two cables should be connected at any one point on an RS485 network, whether the
connections are for devices, converters, or terminal strips.
• Include all segments when calculating the total cable length of a network. If you are not using an
RS485 repeater, the maximum length for cable connecting all devices is 4000 feet (1219.20 meters).
• Connect shield to RS485 Master and individual devices as shown in the figure below. You may also
connect the shield to earth-ground at one point.
• Termination Resistors (R T ) may be needed on both ends for longer length transmission lines. How
ever, since the meter has some level of termination internally, Termination Resistors may not be
needed. When they are used, the value of the Termination Resistors is determined by the electrical
parameters of the cable.
The figure below shows a representation of an RS485 Daisy Chain connection.
40 User and Installation Manual IM02601003E- July 2010 www.eaton.com