WirelessHART: the right standard at the right time

The WirelessHART standard provides a robust wireless protocol for the full range of process measurement, control and asset management applications. Based on the proven and familiar HART protocol, it enables users to quickly and easily gain the benefits of wireless technology while maintaining compatibility with millions of existing devices, also existing tools, asset-management systems and historians.

Key capabilities include:

• Reliability even in the presence of interference, thanks to technology like mesh networking, channel hopping, and time-synchronised messaging. WirelessHART coexistence with other wireless networks is assured.
• Security and privacy for network communications through encryption, verification, authentication, key management and other open industry-standard best practices.
• Effective power management through Smart Data Publishing and other techniques that make batteries, solar and other low-power options practical for wireless devices.

These capabilities, among others, make WirelessHART an excellent approach to meeting users' wireless process automation network needs today.

The WirelessHART standard is part of the HART 7.0 specification and marks an important milestone in the rapid acceptance of wireless technology for process operations.

What is WirelessHART?

WirelessHART is a wireless mesh network communications protocol for process automation applications. It adds wireless capabilities to the HART protocol while maintaining compatibility with existing HART devices, commands and tools.

Each WirelessHART network includes three main elements:

• Wireless field devices connected to process or plant equipment.
• Gateways that enable communication between these devices and host applications connected to a high-speed backbone or other existing plant communications network.
• A network manager responsible for configuring the network, scheduling communications between devices, managing message routes and monitoring network health. The network manager can be integrated into the gateway, host application or process automation controller.

The network uses IEEE 802.15.4 operating at 2.4 GHz. The radios employ direct-sequence spread spectrum technology and channel hopping for communication security and reliability, as well as time division multiple access (TDMA) to ensure latency-controlled communications between devices on the network.

Each device in the mesh network can serve as a router for messages from other devices. This extends the range of the network and provides redundant communication routes to increase reliability.

Building on a Standard

As a standards-based technology, WirelessHART ensures multi-vendor interoperability of a multitude of field devices in process operations.

• Suitability: HART was developed to help users solve process measurement and control problems — problems that are the same whether the solution is wired or wireless. The broad range of wired HART devices available today shows that there are few if any process applications that HART can't handle.
• Familiarity: With more than 24 million HART devices installed around the world, users already have HART tools, training and work practices in place. Far fewer changes are needed than with an entirely new wireless protocol.
• Simplicity: The popularity of HART technology is due in part to how easy it is to implement and use — qualities that will help users quickly gain the benefits of wireless technology.
• Low risk: Starting with an established, proven protocol reduces the risk of unforeseen problems with the technology or development process, enabling users to begin using wireless technology sooner and with greater confidence.

Tools for the job

Like wired HART, WirelessHART supports the full range of process monitoring and control applications, including:

• Equipment and process monitoring
• Environmental monitoring, energy management, regulatory compliance
• Asset management, predictive maintenance, advanced diagnostics
• Closed loop control (when appropriate)

Wireless technology will complement rather than replace wired instrumentation, and plants will often have both operating side by side.

Virtually every process automation requirement is supported by one or more of the wired HART products available today. WirelessHART simply adds another way to communicate with HART devices.

Security

WirelessHART employs robust security measures to ensure the network and data are protected at all times. These measures include:

• Encryption: 128-bit encryption prevents sensitive data from being intercepted.
• Verification: Message integrity codes verify each packet.
• Robust operation: Channel hopping and the mesh infrastructure mitigate effects of jamming and denial-of-service attacks.
• Key management: Rotating keys can prevent unauthorised devices from joining or communicating on the network.
• Authentication: Devices aren't allowed onto the network without authorisation.

WirelessHART security uses today's industry-standard best practices and allows for future enhancements as open industry standards for security evolve.

Other features

Other notable features of WirelssHART are 'smart data publishing' and 'notification by exception'.

Smart data publishing

The HART Protocol has always had the ability to publish process data using 'burst mode'. Smart data publishing enhances this by enabling transmission only when process conditions change or the information is needed by the user's application — greatly improving communication and power efficiency.

Notification by exception

Users are notified automatically when equipment needs maintenance, a device configuration changes, or another event occurs that could jeopardise operations. The information is 'pushed' to users only if such an event occurs.

Emerson Process Management is now shipping WirelessHART products from its Smart Wireless range of pressure, flow, level, temperature, vibration, pH, and discrete transmitters and gateways, as well as the AMS Suite predictive maintenance and Wireless SNAP-ON software, the 375 Field Communicator, and the native wireless interface of DeltaV and Ovation digital systems. The continuous stream of future new products from Emerson will also use the standard, including the soon-to-be-released valve position transmitter, and the Smart Wireless THUM Adapter that will make available stranded diagnostics in legacy devices.

For more information, see www.EmersonSmartWireless.com.