Making WirelessHart visible and transparent

The author: Irene Ruf Product Manager Remote Systems, Pepperl+Fuchs

For anyone wanting to use a WirelessHart network for wireless measurement of process variables, planning seems an unavoidable chore. Investing the time pays off, however, since having a well thought-out network concept will shorten commissioning time significantly. Only finding out at the commissioning stage that the operating range of nodes has been incorrectly estimated and that some nodes are not included in the mesh network makes for time-consuming and difficult trou-bleshooting.

Pepperl+Fuchs offers a 3D simulation tool called Wireless Network Checker (WiNC) as stand-alone software so that this scenario can be avoided altogether. With WiNC, existing 3D plant data can be imported or entire plants created from scratch in the tool itself. The required WirelessHart devices are then positioned as needed before the network is simulated in the tool. This allows the user to see which devices are communicating with each other and where there is no connection, preventing any unpleasant surprises during commissioning since the network has been checked prior to installation.

Once the WirelessHart network has been simulated, the user can be reasonably confident that it will work as a mesh network. The reason for this is that the simulation is not simply based on empirical values; it uses a mathematical race tracking algorithm, which enables the planned network to be calculated with a very high degree of accuracy. The WirelessHart network still has to be connected to the process control system, however. The Pepperl+Fuchs gateway provides two ways of doing this: connection via Modbus or connection to the process control system via EtherNet/IP. Simple tools and methods for establishing the connection quickly and effectively are available in both cases.

With Modbus, the most complicated part is the Modbus mapping. The process control system must know the address at which the Wireless-Hart gateway makes the different data available. The Pepperl+Fuchs gateway offers flexible Modbus mapping in integrated web servers to achieve this. It enables easy Modbus mapping by variables as well as sorting and addressing of nodes. The data generated in this way can also be exported in the form of a CSV file, which can be used for documentation or imported into Excel for further editing. The edited file can then be re-imported by the gateway. During the import, the gateway indicates whether any inadvertent errors such as duplicate addresses have occurred. This provides a quick and straightforward way of checking the Modbus mapping.

Modbus mapping is not necessary when the gateway is connected via EtherNet/IP. In the case of Logix, the Rockwell process control system, the WirelessHart gateway from Pepperl+Fuchs is fully integrated. Nevertheless, the process control system needs to know the addresses of the various nodes. The gateway uses the Hart descriptor for this purpose. The EtherNet/IP address in the Wireless-Hart station is stored there according to a simple structure. This is best carried out when the WirelessHart device is configured using the network ID and join key. The gateway itself has a default address and therefore does not need to be mapped. All that now remains is to tell the process control system the IP address of the gateway and the number of WirelessHart network nodes. The WirelessHart network is then connected to the process control system.

The stage after connection and before commissioning is where the diagnostic tools come in. Once the network has been connected successfully it is commissioned. The WirelessHart network usually builds itself. Unfortunately, wireless connections are not visible to the naked eye, which makes troubleshooting very difficult. Not with the Pepperl+Fuchs gateway, however, which offers graphical network diagnostics directly in the web server. The user is able to see all a device’s connections with other network nodes at a glance. The quality of the connection is indicated at the same time by a colour code. Red means no connection, yellow an acceptable connection and green a very good connection. The intensity of the data traffic on the path can be indicated graphically by the path width. An option also exists to view this data as a list in the web server, since all the information is additionally available in list form. The list can be exported as a CSV file for documentation purposes. The WirelessHart network is thus fully transparent and visible. These handy tools don’t just help with commissioning; they can also be used during operation for diagnostics if the user simply wants to know what has changed in the WirelessHart network. Such changes happen because the network is self-optimising and continually seeks out the best possible paths.

These diagnostic tools in the web server are, of course, also available in the Modbus and EtherNet/IP WirelessHart gateway. Together with the WiNC simulation tool, they make Wireless-Hart visible and transparent for users, regardless of the process control system to which the network is connected.

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