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PROline Prosonic Flow 93 FOUNDATION Fieldbus
Network configuration for FOUNDATION Fieldbus H1
General remarks
Various aspects are to be considered when configuring a FOUNDATION Fieldbus H1
segment and these must essentially be checked by two general types of considera-
tions:
Functional considerations
In the functional considerations, the characteristic of the technical function data laid
down in IEC 61158-2 for the transmission technology of the FOUNDATION Fieldbus H1
and the physical network structure is checked. Here it must always be ensured that the
total base currents of all bus participants does not exceed the maximum permissible
feed current of the bus power supply and that the field devices are always supplied with
a minimum bus voltage of 9 V.
Technical safety considerations
For use of the FOUNDATION Fieldbus H1 in an area with an explosion risk, proof of
intrinsic safety is to be provided for the entire bus segment by means of the technical
safety considerations. Proof of intrinsic safety for the intrinsically safe bus segment can
be made by using one of the following models:
Entity model
The safety considerations correspond to those in a conventional 4...20 mA measuring
circuit. The only exception is that here more than one field device is supplied by the
power supply. The safety considerations must result in the knowledge that the fieldbus
power supply does not exceed the safety parameters (P-, U-, I-values) of the field
devices and that the inductance and capacitance are within the permissible limits
(example see Page 21).
FISCO model
If proof of intrinsic safety is made according to the FISCO model, it is to be verified that
all components connected to the bus segment (field instruments, bus power supplies,
bus terminator) are laid out according to the FISCO model. If this is the case, it must be
proven that for each bus component the values of U
, I
and P
are greater or the same
i
i
i
as the values of U
, I
and P
for the associated equipment (bus power supply). Exam-
o
o
o
ple see Page 28).
Configuration example for a FOUNDATION Fieldbus H1 segment
Based on the following example, the functional and safety-relevant considerations and
calculations for the specification of a FOUNDATION Fieldbus H1 segment are carried
out.
20
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