Honeywell XNX, Technical Manual

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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
configuration� The external interface is installed in the lower left
cable/conduit port of the transmitter and is intrinsically safe (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:
• Meets HART 6�0 physical layer specification
• 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
configurations�
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, configuration parameters, and other device data are
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