Chapter 2 History and Background

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Chapter 2
History and Background
Evolution of HART

The HART protocol
has evolved from a 4–
20mA based protocol
to the current wired
and wireless-based
technology

Includes extensive
features supporting
security, unsolicited
communication of field
device parameters and
advanced diagnostics.

Diagnostics now
include information
about the device and
the equipment that is
being monitored.
Architecture of WirelessHART Mesh Networks

The gateway is the interface
between the wireless
network and the plant
automation application host.

The gateway contains the
network manager that
controls join, configuration,
maintenance and all other
network management
duties.

The security manager
manages the keys used at
both the network layer and
the data link layer
Layered Structure of HART Communication Protocol

In WirelessHART
networks, the
communication stack on
each device is organized
in a layered structure.

Communications are
precisely scheduled using
an approach known as
Time Division Multiple
Access (TDMA).

Scheduling is performed
by the network manager,
which uses overall
network routing
information in combination
with communication
requirements from
individual devices and
applications.
WirelessHART Slot Timing

All transactions
occur in slots
following specific
timing requirements,
and each 10 ms time
slot is further divided
into several sub time
intervals.

This figure shows
one time slot and
provides an overview
of transaction timing
WirelessHART Key Model

Network devices implement
industry standard
encryption, authentication,
verification, anti-jamming
and key management.

The Network management
Network (NWK) layer is
responsible for mesh
networking

Two different scenarios are
shown: 1) a new network
device wants to join the
network and 2) an existing
network device is
communicating with the
network manager.
WirelessHART Sniffer

A wireless “sniffer” may
be used to collect the
network traffic of a
WirelessHART network.

A sniffer was use at the
Separation Research
Program (SRP) plant at
the J.J. Pickle Research
Campus of the University
of Texas, and the data
collected was used to
study the network.
Separation Research Program Processing Equipment

The SRP is an industry supported
consortium focused on fluid mixture
separations. The SRP has continued
to evolve through support from oil,
chemical, biotech, biofuel, food, power
generation and process manufacturing
companies.

At this site a variety of WirelessHART
devices are installed; pH and
conductivity and technology, vibration
analysis and control over wireless.

The WirelessHART installation has
expanded to multiple networks
extending across the process
equipment, the lab, the instrument
shop and the boiler house, which is
located remotely from the main
process plant.
Separation Research Program Processing Diagram

Recent projects include
process technology such
as CO2 separation
illustrated in this figure.

The absorber and the
stripper are 16.8 inches
in diameter and are
approximately 35 feet
tall.

The absorber contains
two beds of packing.
Column temperature is
measured every 12–18
inches, which helps to
monitor column
operations
Device and Network Summary

The HART tag and type for
the devices installed at the
Separations Research
Program (SRP) plant are
summarized in the first two
columns in this table.

The final two columns show
the device Nickname, a 2byte identifier maintained by
the Network Manager, and
the identified neighbor
devices that are installed at
various locations through the
Separations Research
Program (SRP) plan
Network Topology

The devices included in this
study are located in three
locations: the main process
area, the instrument area
and the boiler house.

The boiler house is located
over 300 meters from the
main processing equipment
and can only be reached
through routing devices

The mesh forms
automatically without any
need for site surveys. The
network topology as set up
by the network manager
after two days of use in this
case study is shown in this
figure.
Network Traffic Flow by Hour

For this field test data was
collected by the sniffer over a
45 hour period. During this
period over 750,000 packets
were collected and analyzed.

During the initial two hours of
operation, the network traffic
was largely dominated by
Advertisements.

Once the network forms, the
largest portion of the network
traffic is made up of
measurement data. The
network traffic summary is
plotted by hour in this figure.
Exercise: Accessing a Wireless Gateway
This workshop provides several exercises that can be used to further explore the
information that may be accessed using the built-in webpage provided with the gateway.
In this workshop we will login into the gateway and explore the types of information that
may be accessed. .

Step 1: Open the WirelessHART gateway webpage by typing the gateway IP
address in a web browser. In response a login page will be displayed

Step 2: Type in the account name and password. In response the main web page
will be displayed.

Step 3: Click on different nodes of the hierarchical tree on the left pane to view
different information. For example, through this interface you may access a network
overview, the published device values, the network configuration and the parameters
of a device that are configurable.
Process: Accessing a Wireless Gateway
In this workshop some features are demonstrated for monitoring the performance of a
wireless gateway. Interfaces accessed in the workshop are shown below.
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