The NAMUR organization is an international user association of automation technology in the process industries. They are involved in setting user requirements for many areas of process automation including:
- measurement systems
- process analytics
- process control systems
- communications systems
- operations management
- operational logistics systems
- electrical engineering
I mention this as background for an Industrial Automation Asia article by Emerson’s Jonas Berge, Wireless Meeting Your Needs. In the article, Jonas cites NAMUR’s NE 124 Wireless Automation Requirement:
Recommendation NE124 covers user requirements for wireless in process applications including communication requirements for availability, coexistence and interoperability, security, power, integration into systems, forward and backward compatibility, network management, diagnostics, configuration and commissioning, device replacement, and certification.
I’ll highlight a few of these requirement areas from the article. For availability and reliability, Jonas notes:
WirelessHART [IEC 62591] is a self-organising mesh network, supporting a full multi-hop, multi-path topology. For instance, the process variable from a remote transmitter is relayed from one transmitter to the next… around impenetrable obstacles or RF obstructions, until it reaches the gateway. Multiple paths are maintained such that when a new obstacle appears blocking the path, an alternate path is used for the process variable to reach the gateway. All transmitters, regardless of manufacturer, participate in the mesh topology to ensure reliability needs are met.
With regard to security:
The technologies security measures include encryption, authentication, verification, key rotation, and sequence numbers. Most importantly, security cannot be turned off; it is always on. Commissioning a wireless transmitter includes assigning a secret join key (password) which should not be done wirelessly. All WirelessHART transmitters have a wired HART maintenance terminal where the handheld field communicator or laptop interface that all plants already have can be connected to securely commission the transmitters before any wireless communication commences.
For the coexistence requirements [hyperlinks added]:
WirelessHART uses the IEEE 802.15.4 standard radio which uses Direct Sequence Spread Spectrum (DSSS) modulation enabling coexistence with other wireless networks. Additionally, the technology uses channel hopping as well as channel black listing, further improving its ability to coexist with other radios.
For automation system integration [hyperlink added]:
Plants already have digital devices using hardwiring and bus integrated in intelligent device management software, predominantly using Device Description (DD) or the newer enhanced Electronic Device Description Language (EDDL) device integration technology… use a wireless technology that supports the EDDL standard, such that a single common system software application supports configuration and diagnostics for wireless transmitters from multiple vendors as well as the wired system in place today.
Finally, for wireless network management:
Use a gateway that tracks communication statistics such as missed updates, discarded updates, reliability, path stability, signal strength, latency, number of re-joins, and timestamp for last join, as well as maintains a ‘live list’ with node state, and if service is denied due to network load. Also use network management software which continuously monitors network health and battery status, and displays it graphically for an easy overview of problem locations.
Read the article for additional ways the IEC 62591 WirelessHART technology maps back to the NE124 user requirements in some of the other areas including real-time performance, interoperability and interchangeability, version and lifecycle management, battery, and products and software.