In process automation applications, wireless networks enable tremendous flexibility while also leading to significant cost reductions. WirelessHART technology is one of the key contributors that help you to reap these benefits. In a WirelessHART network structure, field devices connect with WirelessHART adapters which communicate with the process control system via WirelessHART gateways.
Pepperl+Fuchs' WirelessHART MODBUS gateway with updated software makes installation, commissioning, and diagnosis of these wireless networks even easier for you.
A central element of the updated software is the integrated Stale Values and Substitution Values. These parameters enable you to quickly react to a failure and to precisely evaluate possible solutions for application specific errors.
The Stale Value displays the age of a submitted value. This can be a dynamic variable and the status information of a connected field device. Every last burst message the WirelessHART gateway receives from the field is assigned a time stamp. This allows it to calculate a percentage value from the burst period for every temporarily saved value. Once the gateway receives a new value from the field device, the count restarts.
Individually defined warning levels (e.g. 150% burst period) or error levels (e.g. 300% burst period) trigger alarms when a burst message has exceeded its update cycle. Color-coded notifications allow you to quickly identify whether the measured value is not older than 100% (green), temporary communication problems exist (orange), or you are facing a complete communication breakdown (red).
To tackle these failures, a substitution value can be determined for each HART variable. These Substitution Values can either be the last measured value, “NaN” (“Not a number”), “upscale =0x7F7FFFFF”, or “downscale 0xFF7FFFFF”. Furthermore, a definition of individual Substitution Values is possible as well. This allows you a situational and quick error diagnosis.
Another bonus feature for the WirelessHART gateway is the addition of the “Factory Acceptance Test” (FAT) which is applied during commission. By using the Substitution Values, the FAT simulates if a WirelessHART gateway is submitting the correct values like PV, SV, TV, QV, and loop current to the control system.
If the process control receives the values defined in the gateway, the acceptance test is successfully passed and field devices and WirelessHART adapters can be added to the network.
Different user roles ensure that plant operators can only monitor and update values, while administrators have read and write permissions, making manipulation of the WirelessHART network practically impossible. In addition to join key and network ID, a whitelist ensures that only permitted participants can join the network. Operational stafff can expand this whitelist when participants have to be added to the network. If you have an external provider handling your network expansions, you can also grant access with a temporary join key which is deactivated automatically after a certain time.
Another option for you is to permanently reassign a new join key for all connected network participants. This is done without having to reintegrate the adapters to the network via HART modem, offering you increased safety when the circle of users changes—for instance after commissioning or maintenance work by external providers.