KROHNE H250 M40 FOUNDATION FIELDBUS - Manual (Page 9)

ELECTRICAL CONNECTIONS
3
9
H250 M40
www.krohne.com 02/2014 - 4001208201 - AD H250 M40 FF R02 en
3.4 Cable types
The cable types are specified according to IEC 61158-2. Shielded cables offer the advantage of
malfunction-free operation with adequate protection against electromagnetic influences, and
make it possible to employ the full performance of the Foundation Fieldbus system.
In non-hazardous areas the maximum number of field devices is limited to 32. For detailed
information refer to the following table.
In non-hazardous areas the ignition protection class of the devices and the limited electric power
available limit the number of field devices to 4.
All bus segments must be fitted with a terminator at both ends.
3.5 Shielding and grounding
• For optimum electromagnetic compatibility of systems it is extremely important that the
system components, and particularly the bus cables connecting the components, are
shielded and that such shields - if possible - form an unbroken cover.
• In Ex systems an adequate equipotential bonding in the hazardous and non-hazardous
location along the entire Fieldbus installation is strongly recommended.
• Minimum requirement for EMC is a one-sided grounding of the shield on the “master” side.
Multiple grounding of the shield is of advantage.
Core cross-section 0.8 mm 2 or
AWG 18
0.32 mm 2 or
AWG 22
0.13 mm 2 or
AWG 26
1.25 mm 2 or
AWG 16
Cable type A A A A B B B B C C C C D D D D
twisted pair,
individually
shielded
individual or
multiple twisted
pairs with overall
shield
multiple twisted
pairs, without
shielding
multiple non-
twisted cables,
without shielding
Max. length
incl. branch line
1900 m / 6200 ft 1200 m / 3900 ft 400 m / 1300 ft 200 m / 650 ft
Number of devices Cable lengths for number of devices per branch line
1 device 2 devices 3 devices 4 devices
25...32 1 m / 3.3 ft 1 m / 3.3 ft 1 m / 3.3 ft 1 m / 3.3 ft
19...24 30 m / 100 ft 1 m / 3.3 ft 1 m / 3.3 ft 1 m / 3.3 ft
15...18 60 m / 200 ft 30 m / 100 ft 1 m / 3.3 ft 1 m / 3.3 ft
13...14 90 m / 300 ft 60 m / 200 ft 30 m / 100 ft 1 m / 3.3 ft
1..12 120 m / 400 ft 90 m / 300 ft 60 m / 200 ft 30 m / 100 ft
INFORMATION!
The use of twisted and shielded cables is strongly recommended, otherwise EMC protection of
the signal converter cannot be assured.
AD_H250_M40_FF_R02_en_4001208201_PRT.book Page 9 Friday, February 21, 2014 11:25 AM