Pepperl+Fuchs KFD Series, Manual

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HART Multiplexer System KFD*-HM*-16
System Description
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3.2 Possible Applications
General Applications
In process engineering plants, many field devices are distributed over a large area.
The characteristic values of these field devices must be monitored and logged or adjusted if
process variables are changed.
The HART multiplexer system from Fuchs enables communication between a
computer or a process control system and field devices that support the HART protocol.
The following figure shows the basic system structure.
Figure 3.2 Basic structure
HART-compatible field devices allow information such as the measuring range and device
address to be saved in the field device itself. Access to this data is usually achieved with a
handheld. This means that a connection to the field device must be established manually for
each value to be changed.
If certain data has to be logged as part of quality assurance processes, this increases the effort
for the process control system. For example, the relevant data has to be requested cyclically
and saved in a database by the system.
The HART multiplexer system establishes the connection between the computer and the
HART-compatible field devices. All access to the field device takes place parallel to the
transmission of the 4 mA to 20 mA signal and therefore has no affect on the processing of
measured values by the process control system.
The system provides a subordinate service level. The HART multiplexer system can also
detect measured values. For field devices that are mounted in hazardous areas,
the connection takes place on the non-hazardous side of the control unit.
Fuchs offers corresponding control units, e. g., KCD2-STC-**, KCD2-SCD-**.
The HART multiplexer system can also be connected to control units from other
manufacturers. Existing plants can therefore be extended very easily, taking full advantage of
the HART communication.
The system can consist of a maximum of 31 HART multiplexer devices that are connected to a
computer via an RS-485 interface. Each multiplexer master can manage up to
15 multiplexer slaves. Each device, regardless of whether it is a multiplexer master or
multiplexer slave, establishes the connection to 16 field devices. One computer can therefore
be used to address up to a maximum of 7936 field devices.
Operation using a handheld is still possible, since the HART protocol accepts two masters in
one system, i. e., a computer and a handheld.
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KFD0-HMM-16
Field devices Host
Computer-based
maintenance station
or process control system
HART communication 1 HART communication 2
HART multiplexer system