2. Installation and Wiring
11
Serial Bus Cable Wiring
The signals passing through the serial bus cable (twisted pair cable with shield) are low voltage
type.
The desirable order of priority of wiring routes is given below. Use the exclusive serial bus route
(1) as much as possible.
(1) Use the exclusive serial bus route.
(2) Use the exclusive system route.
(3) Use the general instrumentation route.
(4) Use the shield duct.
The shielded twisted pair cable specifications are given in Table 2.1.
Table 2.1 Shielded twisted pair cable specifications
Item Specification
Minimum insulation resistance
10 M
km
Characteristic impedance
100
Minimum allowable bending radius 25 mm
Precautions in serial bus wiring
Observe the following precautions in wiring the serial bus cable.
The wiring should be confined to the same cabinet or at most 2 jointed cabinet, and have total
length within 30 m.
As a rule, multi-drop wiring from the controller.
If the cable is to be bent, observe the specified minimum bending radius (see Table 2.1), or
cable vender’s recommendation.
Precautions in extending the serial bus, for example when expanding the system
Observe the following precautions when expanding the intelligent PI/O system.
Keep the total length of serial bus wiring within 30 m.
If wiring must unavoidably extend outside the cabinet, always observe the "wiring inside
cabinet" precautions of wiring outside cabinet.
When adding another communication base unit, note that the maximum number that can be
connected is 15.
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