Draft standard: What’s in the April ’07 WirelessHART specification

By Control Engineering Staff March 27, 2007

Orlando, FL —Should you grab a wireless network that works and gain benefits or wait for an emerging standard? If you haven’t jumped in yet, or even if you have, here’s what you can expect from the WirelessHART specification due next month. Resulting products are expected by year-end 2007.

HART Communication Foundation has been preparing a standard for HART wireless based on IEEE 802.15.4 , for low power 2.4 GHz operation, expecting a huge need for wireless instrumentation. ARC Advisory Group’s Will Chin predicts that by 2011 embedded intelligence in instrumentation will double, 40% of devices will be wireless, wireless will add 20% more new devices to a plant. Chin says more than half of installed devices will be interoperable, most applications will be monitoring types, and non-critical control using wireless will lag behind monitoring.

According to Ed Ladd, HART Communications Foundation director of technology programs, wirelessHART is under development because there is “no standard that’s deterministic enough for our needs in process control and instrumentation.” Ladd updated progress on the draft standard at the ABB Automation World 2007 users’ conference on March 21. The final specification will be public at end of August, general devices will be available at the end of the year, and safety devices will be ready in early 2008.

Ladd said the draft WirelessHART specification for process automation applications, begun in 2005, will include:

  • 99% reliability;

  • Wireless hardware with 3-10 yr battery life;

  • Mesh, star, and combined networks, rather than just point-to-point;

  • Backward compatibility with all equipment in the field now to complement, not replace, wired HART. Plans for the spec include an open and interoperable architecture using the same configuration, maintenance, diagnostic tools, and procedures;

  • More information in real time. Just 10-15% of HART devices are continuously monitored at present. Wireless capability would give easier access to new intelligent device and process information; multivariable process data; and status, diagnostic, and configuration data. This would result in improved asset management, environmental monitoring, energy management, regulatory compliance, and access to remote or inaccessible equipment (personnel safety).

  • More flexibility. Wireless adapter can be attached anywhere on loop. Key part is getting information out without necessarily throwing out the legacy system that’s in there.

  • Better security, in the form of encryption (using AES128), anti-jamming (to mitigate denial of service), key management, and authentication. Verification would be improved with message integrity codes(MICs) that are generated after data are encrypted to sign the data end to end; and

  • Same radio as ZigBee, modified to work better, and frequency hopping spread spectrum technology in a self-organizing, self-healing mesh using short packets except in burst mode.

Those involved in developing this standard include end users and ABB, Adaptive Instruments, Emerson, Siemens, Coronis, Dust Networks, Elpro, Endress+Hauser, Flowserve, Honeywell, MacTek, Omnex, Pepperl+Fuchs, Phoenix Contact, Smar, and Yokogawa.

Ladd expects the standard to complement rather than compete with the broader and not as far along ISA-SP100, Wireless Systems for Automation standard also underway. Many of the same companies are involved, he said.

” Smart about HART communications? Apply for plant of the year ” outlines related opportunities and benefits of being HART smart. About 22 million HART devices are in the field, Ladd says, growing at 2 million a year.

For related news from the conference, also read, ” ABB users say: Don’t wait for a disaster to upgrade instrumentation .”

Mark T. Hoske , editor in chief,
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