Endress+Hauser iTEMP TMT 165 FOUNDATION Fieldbus Betriebsanleitung Seite 88

4 Wiring
88
Cable structure
Wire size
Loop resistance
(DC)
Impedance at
31.25 kHz
Attenuation at
39 kHz
Capacitive unsymmetry
Envelope delay distortion
(7.9 to 39 kHz)
Shield coverage
Max. cable length (incl.
spurs >1 m)
Suitable fieldbus cables from various manufacturers for the hazardous area are listed
below:
• Siemens: 6XV1 830-5BH10
• Belden: 3076F
• Kerpen: CeL-PE/OSCR/PVC/FRLA FB-02YS(ST)YFL
Maximum overall cable length
The maximum network expansion depends on the type of ignition protection and the
cable specifications. The overall cable length combines the length of the main cable
and the length of all spurs (>1 m). Fig. 5-1 on page 94 shows the structure of a fieldbus
network. Note the following points:
• The maximum permissible overall cable length depends on the cable type used (see
table above).
• If repeaters are used the maximum permissible cable length is doubled.
A maximum of three repeaters are permitted between user and master.
Maximum spur length
The line between distribution box and field unit is described as a spur.
In the case of non ex-rated applications the max. length of a spur depends on the
number of spurs (>1 m):
Number of spurs
Max. length per spur
Number of field devices
According to IEC 61158-2 a maximum of 32 field devices may be connected per
fieldbus segment. However, this number may be restricted in certain circumstances
(type of ignition protection, bus power option, current consumption of field device).
A maximum of four field devices can be connected to a spur.
Shielding and grounding
The optimum electromagnetic compatibility of systems is only guaranteed if system
components and in particular lines are shielded and the shielding provides the most
complete coverage possible. Shield coverage of 90% is ideal.
FOUNDATION Fieldbus temperature transmitter
Type A
Twisted pair,
shielded
2
0.8 mm
(AWG 18)
44 Ω/km
100 Ω ± 20%
3 dB/km
2 nF/km
1.7 µs/km
90%
1900 m
* not specified
1...12 13...14
120 m 90 m
Type B
Single or lore twisted pairs, fully
shielded
2
0.32 mm
(AWG 22)
112 Ω/km
100 Ω ± 30%
5 dB/km
2 nF/km
*
*
1200 m
15...18 19...24
60 m 30 m
Endress+Hauser
25...32
1 m