FMC Corporation - Talstar 80 - Handbuch (Seite 26)

Wiring Proline Promass 80 PROFIBUS PA
26
4 Wiring
#
Warning!
When connecting Ex-certified devices, see the notes and diagrams in the Ex-specific supplement to
these Operating Instructions. Please do not hesitate to contact your FMC Technologies sales office
if you have any questions.
!
Note!
The device does not have an internal power switch. For this reason, assign the device a switch or
power-circuit breaker which can be used to disconnect the power supply line from the power grid.
4.1 PROFIBUS PA cable specifications
4.1.1 Cable type
Twin-core cables are recommended for connecting the device to the fieldbus. Following
IEC 61158-2 (MBP), four different cable types (A, B, C, D) can be used with the 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 type B multi-pair cables, it is permissible to operate
multiple fieldbuses with the same degree of protection on 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.
Suitable fieldbus cables 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
Type A Type B
Cable structure Twisted pair,
shielded One or more twisted pairs, fully shielded
Wire cross-section 0.8 mm
2
(AWG 18) 0.32 mm
2
(AWG 22)
Loop-resistance (DC) 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 μs/km *
Shield coverage 90% *
Max. cable length (incl. spurs >1 m) 1900 m (6200 ft) 1200 m (4000 ft)
* Not specified