
6-7
Cabling and Wiring the System
SIMATIC 545/555/575 System Manual
Table 6-1 lists the characteristics of the Belden cables recommended for
Series 505 installations.
Table 6-1 Series 505 Cable Characteristics
Belden
Cable Type
Center
Conductor
Outside
Diameter
Impedance Capacitance Velocity
9860
16 AWG solid
13.8 ohm/km
0.44 in.
11.2 mm
124 ohms 35.8 pf/m 0.78 c
9271
25 AWG 7x33
104.3 ohm/km
0.24 in.
6.1 mm
124 ohms 40 pf/m 0.66 c
9182
(89182)
22 AWG 19x34
46 ohm/km
0.35 in.
8.9 mm
150 ohms 28.9 pf/m 0.78 c
The cable you use should have a specified characteristic impedance between
100 and 150 ohms, 124 ohms being optimum. Also look for the following
features in the cable you select:
• A high uniform twist and spacing of conductors (usually found in cables
called “twin axial”).
• Shield coverage approaching 100%.
• DC resistance of the installed cable length smaller than the
characteristic impedance.
• A jacket suitable for the installation.
NOTE: When selecting cable connectors, be aware that shells with strain
relief provide the most dependable long-term operation.
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