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Series 302 FIELDBUS FOUNDATION – Installation, Operation and Maintenance Manual
1.16
Figure 1.20 – Several Grounding and Shield Ways
Quantity of Foundation Fieldbus Equipments in a H1 Segment
The amount of equipments (N) for segment is a function of the quiescent consumption of each H1
equipment, the involved distances (type A cable loop resistance: 44 O/km), the drained current, of
the area classification, besides the FDE current (usually 0 mA, depending on the manufacturer). The
total segment current should be smaller than the one drained by the power supply. Smar devices
consume 12 mA.
FREE
FDE
BN
Seg
I
I
I
I
+
+
∑
=
Because:
C
Seg
I
I
〈
Where:
Seg
I
: H1 segment current;
BN
I
∑
: Sum of the quiescent currents of all the devices in the H1 segment;
FDE
I
: Additional current in case of failure, usually negligible;
FREE
I
: Recommended: 20 mA, rest current useful in case of expansion or change of manufacturer
C
I
: Drained current.
Besides, it is recommended more than 9.0 V in the terminal block of the H1 device most distant from
the PSI to guarantee its powering and correct communication:
Содержание FY302
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