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Bus termination
The start and end of each fieldbus segment are always to be terminated with a bus ter-
minator.
• In the case of a branched bus segment the measuring device furthest from the seg-
ment connector represents the end of the bus.
• If the fieldbus is extended with a repeater then the extension must also be terminated
at both ends.
Selecting and connecting components
The FOUNDATION Fieldbus allows several devices from different manufacturers to be
generally connected to a bus segment. When selecting components for use in areas
with an explosion risk only components marked as intrinsically safe, explosion-pro-
tected electrical equipment or as intrinsically safe associated electrical equipment may
be used. When combining different fieldbus devices and fieldbus components, in addi-
tion to functional considerations, technical safety factors must be considered if explo-
sion protection is to be ensured.
Implementation of intrinsic safety in the
FOUNDATION Fieldbus H1
The FOUNDATION Fieldbus H1 can be made intrinsically safe for use in areas with an
explosion risk (EEx i). To do this, according to the FOUNDATION Fieldbus specification
a suitable safety component must be installed (FF-816) between the safe area and the
area with an explosion risk. The intrinsically safe bus segment can be supplied either
by a non-intrinsically safe power supply with a safety barrier downstream or by a field-
bus power supply with an intrinsically safe output.
It is recommended that the cable shielding be grounded at both ends (refer to Fig. 2,
Page 6).
Installation example of a galvanic isolator with bus feed:
5
+
+
+
T
–
r
Esc
-
+
E
4
Fig. 7:
Typical embodiment of a galvanic isolator including fieldbus power supply
1 = DCS with integrated FOUNDATION Fieldbus H1 interface card
2 = fieldbus power supply: galvanic isolator
3 = fieldbus power supply
4 = Prosonic Flow 93 bus devices for hazardous area
5 = terminator (T) = bus termination
PROline Prosonic Flow 93 FOUNDATION Fieldbus
E X
E X
+
+
–
r
r
Esc
Esc
-
+
E
-
+
E
2
1
+
+
Fieldbus
Foundation
–
–
–
+
DC
3
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