9
3-3. F
oundation
Fieldbus™ cable specification
3-3-1. Cable type
Twin-core cables are required for connecting the device to the Foundation Fieldbus™ H1.
Following IEC 61158-2 (MBP), four different cable types (A, B, C, D) can be used with the
Foundation Fieldbus™, only two of which (cable types A and B) are shielded.
Cable types A or B are particularly preferable for new installations. Only these types have
cable shielding that guarantees adequate protection from electromagnetic interference and
thus the most reliable data transfer. In the case of cable type B, several field buses (same
degree of protection) may be operated in one cable. No other circuits are permissible in the
same cable.
Practical experience has shown that cable types C and D should not be used due to the lack
of shielding, since the freedom from interference generally does not meet the requirements
described in the standard.
The electrical data of the fieldbus cable have not been specified but determine important
characteristics of the design of the fieldbus, such as distances bridged, number of users,
electromagnetic compatibility, etc.
Type A
Type B
Cable structure
Twisted pair, shielded
One or more twisted
pairs, fully shielded
Wire size
0.8 mm
2
(AWG 18)
0.32 mm
2
(AWG 22)
Loop-resistance (direct current)
44 Ω/km
112 Ω/km
Characteristic impedance at 31.25 kHz
100 Ω ± 20%
100 Ω ± 30%
Attenuation constant at 39 kHz
3 dB/km
5 dB/km
Capacitive asymmetry
2 nF/km
2 nF/km
Envelope delay distortion (7.9 to 39
kHz)
1.7 ms/km
*
Shield coverage
90%
*
Max. cable length (incl. spurs >1 m)
1900 m (6233 ft)
1200 m (3937 ft)
* Not specified
Suitable fieldbus cables (type A) from various manufacturers for non-hazardous areas are
listed below:
Siemens: 6XV1 830-5BH10
Belden: 3076F
Kerpen: CeL-PE/OSCR/PVC/FRLA FB-02YS(ST)YFL