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.