Installation Guide

3-44
40
10.5
17
27
68.5
50
8.5
13.5
21.5
55
60
7
11
18
45.5
70
6
9.5
15.5
39
80
5
8.5
13.5
34
90
4.5
7.5
12
30.5
100
4
6.5
10.5
27.5
110
3.5
6
9.5
24.5
120
3.5
5.5
8.5
22.5
RS-485 Serial Cable
It is recommended to use the following materials for RS-485 serial cables:
 UL-certified twisted pair cables that meet the standards of UL2464 and UL20276.
 Category-3 and higher cables that meet the overall cabling standards. The cable core can range
from 22 to 28 American Wire Gauge (AWG). 24 AWG and 26 AWG are recommended.
The impedance of the cable should be in the range from 90 ohm to 150 ohm. The RS-485 port
supports long distance communication; however, you must ensure that the overall cable attenuation
is no more than 6 dB. For an encoder or a decoder, the total cable length should be no more than
900 m (2952.76 ft.), and the baud rate is recommended to be no more than 9600 bps. If a higher
baud rate is required, choose the cable length according to the following table. If a too long cable is
required, it is recommended to use repeaters to extend the transmission distance. A T-shape or
Z-shape connection is preferred, or a star-shaped connection is adopted after an RS-485 hub is
deployed at the device side.
Table 3-5 Maximum length of an RS-485 serial cable at different baud rates
Baud Rate (bps)
Maximum Length
1200, 2400, 4800, 9600, 19200
900 m (2952.76 ft.)
38400
850 m (2788.71 ft.)
57600
550 m (1804.46 ft.)
76800
400 m (1312.34 ft.)
115200
250 m (820.21 ft.)