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2.1.4
Galvanic isolation
The voltage supply, the analogue signals and the RS 485 interface are galvanically separated. This galvanic
isolation is achieved through the use of transformers and opto couplers.
For the direct current components, the individual HART channels are isolated by means of capacitors. Thus
the 4 mA ... 20 mA signal is not affected.
The connected current repeaters are galvanically interconnected unilaterally through the com-
mon ground connection of the analogue signals.
If the galvanic isolation is to be properly maintained, the individual ground cables must be isola-
ted by capacitors. Suitable Fl and MB boards can be supplied by Pepperl+Fuchs for this pur-
pose.
Notwithstanding the common ground connection of the analogue signals from the masters/slaves, the gal-
vanic isolation of the current repeaters is secured if
•
FI and MB boards are used, which are fitted with capacitors.
•
KFD2-STC4-Ex1 or KFD2-STC4-Ex2 Ex isolation modules are used as current repeaters.
2.1.5
Cabling for the analogue signals
The individual I/O components of the HART product family are connected by a single 26-pin system plug
connector for the connection of the individual current repeaters (for plug pin assignmentsee section 6.2).
Pepperl+Fuchs provide specially developed connector units (HART interfaces type FI-***) for this purpose.
As required, the connection to these units can be via a system cable or even by means of conventional
screwconnections. If the current repeaters are mounted on a motherboard (MB-***), the connection is made
directly from the board to the multiplexer via a flat cable type K-HM26.
The control system is connected via a system specific connector of the motherboard or the Flex-interface.
Flex-interfaces with screw terminals are available for the purpose of individual wiring.
2.1.6
Device function
The software functions described in this section are normally integrated into the operating soft-
ware for the servicing station, i.e. the functions are not generally (de-)activated via the descri-
bed HART commands. In contrast the operating software uses functions (menu commands) to
control these procedures. However the basic HART commands are described as well, because
the functions may be named different in the various operating softwares and the basic function
may not be obvious. Information on the supported commands can be found in section 6.1.
Channel number
The HART multiplexer master KFD2-HMM-16 provides 16 channels for the connection of "smart" transmit-
ters or control devices, which support digital communication in accordance with the HART specification. A
maximum of 15 additional KFD0-HMS-16 slaves can be connected, each of which in turn support 16 chan-
nels. Thus in a full assembly, a loop of 256 channels can be achieved with just one master. When using the
multiplexer master with the RPI product family, no slave units are necessary. On RPI, communication takes
place via the power rail.
Multiplexer table (module table)
The multiplexer master and the connected multiplexer slaves must be designated as 'available' in a multi-
plexer table (command 157). Only those modules defined as 'available' in this table are used in the commu-
nication process. The multiplexer table consists of 16 bit, one for each possible multiplexer address
(default: module 0 (master) and 1 activated).
Subject to reasonable modifications due to technical advances.
Pepperl+Fuchs Group • Tel.: Germany (06 21) 7 76-0 • USA (330) 4 25 35 55 • Singapore 7 79 90 91 • Internet http://www.pepperl-fuchs.com
HART Multiplexer Master KFD2-HMM-16
Copyright Pepperl+Fuchs, Printed in Germany
Product description
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