Alternate Cables; Table 4-3 Cable Characteristics - Siemens SIMATIC TI555 System Manual

Alternate Cables

TI545/TI555 System Manual
Three commercially available cables provide an acceptable level of I/O
communication in an industrial environment when used in accordance with
Table 4-2.
Belden cable 9860 is a large conductor cable that provides a low
attenuation and distortion for long trunk lines.
Belden cable 9271 is a smaller and more flexible cable suitable for short
trunk lines and all drop line cables.
Belden cable 9182 provides an intermediate level of size, flexibility, and
useful length. The 9182 cable is also available in a version (89182)
rated for a higher level of fire resistance and low smoke producing
properties.
Alternate cables should have a specified characteristic impedance between
100 and 150 ohms; 124 ohms being optimum. Other considerations for
alternate cables include: a high uniform twist and spacing of conductors
(usually found in cables called "twinaxial"), shield coverage approaching
100%, DC resistance of the installed cable length smaller than the
characteristic impedance, and a jacket suitable for the installation.
Characteristics of the cables listed in Table 4-2 are provided in Table 4-3 as
a guide for selecting alternate cables.

Table 4-3 Cable Characteristics

Belden Center
Cable Type Conductor
16 AWG solid
9860
13.8 ohm/km
25 AWG 7x33
9271
104.3ohm/km
9182 22 AWG 19x34
(89182) 46 ohm/km
Outside
Impedance Capacitance Velocity
Diameter
11.18 mm 124 ohms
6.15 mm 124 ohms
8.89 mm 150 ohms
Cabling and Wiring the System
35.8 pf/m 0.78 c
40 pf/m 0.66 c
28.9 pf/m 0.78 c
4-13