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XNX Universal Transmitter
Section 2 - Installation and Operation
51
2.3 Options
2.3.1 Local HART Interface
Available with any sensor technology or option, this option
provides an external access to the HART interface in the
transmitter. An IS barrier inside the transmitter allows the user to
attach an external hand-held interrogator for programming and
conguration.Theexternalinterfaceisinstalledinthelowerleft
cable/conduitportofthetransmitterandisintrinsicallysafe(IS).
Figure 56. XNX Universal Transmitter with HART Interface IS Barrier installed
The HART protocol is a communication technology used with
smart process instrumentation, providing two-way digital
communication simultaneously with the 4-20mA analog signaling
used by traditional instrumentation equipment. For more
detailed information on HART, see the HART Protocol and www.
hartcomm.org.
Implementation of the HART protocol in the XNX transmitter:
•
MeetsHART6.0physicallayerspecication
• The physical layer is tested according to HART Physical
Layer Test Procedure, HCF_TEST-2.
• Data transfer rate: 1200 bps.
HART devices can operate in point-to-point or multidrop
congurations.
Caution: Device address changes must be performed only by
qualified service personnel.
Point-to-Point Mode
In point-to-point mode, the 4–20 mA signal is used to
communicate one process variable, while additional process
variables,congurationparameters,andotherdevicedataare
transferred digitally via HART protocol (Figure 57). The 4–20 mA
analog signal is not affected by the HART signal.
Control System
or Other Host Application
Multiplexer
Barrier
Handheld Terminal
Field Device
Note: Instrument power is provided by an interface
or external power source that is not shown.
Figure 57. Point-to-Point Mode of Operation
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