Siemens SITRANS T3K PA Instruction Manual page 110

7NG3213
7.3 Properties of the PROFIBUS-PA
The PROFIBUS-PA enables bidirectional communication of a bus master with the
field devices via a screened two-wire line. At the same time the power is supplied
to the two-wire field devices on the same lines (current I in Figure 7, page 109).
Profile
Supplementary to the EN standard 50170, the PNO (PROFIBUS User
Organisation) has defined the functionality of the individual field device types in a
so-called profile description. This profile defines minimum functional requirements
and optional extensions. The device-internal "Device Management" supplies the
configuration tool of the control system with all the necessary basic information for
finding the profile parameters. With this a parametering tool can operate all profile-
conform devices no matter of what type and manufacture.
Depending on the size of the system and thus the number of field devices, the
system must be implemented with one or more PROFIBUS-PA channels.
A PROFIBUS PA channel consists of the components shown in Figure 8.
Control stand
PLS, PC
Legend:
T Terminating resistor
FD Field device
PC Personal Computer
PLS Process control system
Figure 8 PROFIBUS--PA architecture
110
PROFIBUS-DP
Coupler
T
Power
supply
Instruction Manual
Field
PROFIBUS-PA
FD FD
C79000-B7174-C55-04
T
additional
SITRANS T3K PA