Siemens DS Betriebsanleitung Seite 30

Operating Instructions
When using the recommended bus cable, the maximum length (total of all
sections) is 1900 m (see also Section 2.1). The individual field devices FD
can be connected to almost any position. Further information can be
obtained from the "PNO Manual PROFIBUS-PA"
Each field device has a separate address on the PROFIBUS-PA so that they
can be differentiated from one another.
The maximum number of devices which can be connected to a bus line
depends on the current consumption and the respective application. When
operating in potentially explosive atmospheres, intrinsic-safety is only
guaranteed if the maximum power supply applied to the bus does not
exceed the following voltage and current values:
· EEx ib IIC
· EEx ib IIB
! Warning
Only certified power supply units may be used to power the
intrinsically-safe PROFIBUS-PA.
If the complete bus with all connected stations is located outside the poten-
tially explosive atmosphere, the maximum bus supply may be 30 V /
500 mA.
The number of devices which can be connected to a bus line can be
determined from the total of the maximum current consumptions of the
connected devices (≥ 10 mA per device according to the standard) and the
available current. A current reserve of at least 20 mA should be present for
safety reasons. The electronic current limiting present in the SITRANS P
guarantees that the bus is not overloaded in the event of a fault, and that
communication is still possible with the remaining stations.
2
Can be ordered from the PNO office, Haid-und-Neu-Str. 7, D-76131 Karlsruhe;
Order No. 2.091
26
Current I < 128 mA, voltage U
P
Current I < 280 mA, voltage U
P
2
.
< 15 V
S
< 15 V
S
SITRANS P
C79000-B5674-C207-1