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7 RS-485 Installation and set-up
7.1.1 Overview
RS-485 is a two-wire bus interface compatible with multi-
drop network topology, i.e., nodes can be connected as a
bus, or via drop cables from a common trunk line. A total
of 32 nodes can be connected to one network segment.
Network segments are divided up by repeaters. Please
note that each repeater functions as a node within the
segment in which it is installed. Each node connected
within a given network must have a unique node address
across all segments.
Terminate each segment at both ends, using either the
termination switch (S801) of the unit or a biased
termination resistor network. Always use shielded twisted
pair (STP) cable for bus cabling, and always follow good
common installation practice.
Low-impedance ground connection of the shield at every
node is very important, also at high frequencies. This can
be achieved by connecting a large surface of the shield to
ground, by means of a cable clamp or a conductive cable
connector, for example. It may be necessary to apply
potential-equalizing cables to maintain the same ground
potential throughout the network, particularly in instal-
lations where there are long lengths of cable.
To prevent impedance mismatch, always use the same
type of cable throughout the entire network.
Cable: Shielded twisted pair (STP)
Impedance: 120 Ohm
Cable length: Max. 3,396 ft [1,200 m] (including drop lines)
Max. 1,640 ft [500 m] station-to-station
7.1.2 Network Connection
Connect the unit to the RS-485 network as follows (see
also diagram):
1. Connect signal wires to terminal 68 (P+) and
terminal 69 (N-) on the main control board of the
unit.
2. Connect the cable screen to the cable clamps.
NOTE!
Shielded, twisted-pair cables are recommended in order to
reduce noise between conductors.
130BB022.10
61 68 69
Figure 7.1 Network Terminal Connection
130BB021.10
12 13 18 19 27 29 32 33 20 37
Remove jumper to enable Safe Stop
61 68 69 39 42 50 53 54 55
Figure 7.2 Control card terminals
7.1.3 RS-485 Bus Termination
Use the terminator DIP switch on the main control board
of the unit to terminate the RS-485 bus.
RS-485 Installation and set... VLT Active Filter AAF 00x
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