Wiring Instructions
82/86
netTAP NT 50 | Gateway Devices
DOC091202UM09EN | Revision 9 | English | 2013-02 | Released | Public
© Hilscher, 2010-2013
Bus requirements:
The bus cable must be a shielded twisted pair cable where the shield
should be connected at both ends with large contact areas to the potential
equalization system.
On each end, the bus requires a termination resistor (LT) between the lines
D1 und D0 of approximately the amount of the characteristic wave imped-
ance of the cable, which usually amounts to a value between 120
Ω
and
220
Ω
.
The pull-up and pull-down resistors should have a value of 390
Ω
up to
650
Ω
.
Cable requirements:
The workmanship of bus cabling is an important factor of the reliable opera-
tion and also for the electromagnetic compatibility and emission. It is man-
datory to use shielded twisted-pair cables. The shield of the cable must
consist of a copper wire mesh.
Parameter
Value
Characteristic wave
impedance
150
Ω
± 15
Ω
Capacitance
< 30 pF/m
Loop resistance
110
Ω
/km
Wire gauge
0,64 mm
Table 80: Electric Requirements to RS-485 Cables
The following lengths of lines can be achieved:
Max. overall length of
line
Max. Baud rate
Max. length of a single
branch line
120 m
1 MBit/s
0,3 m
600 m
500 kBit/s
0,6 m
1200 m
100 kBit/s
1,5 m
Table 81: RS-485 Cable Lengths
