The start of the climb toward International Electrotechnical Commission (IEC) standardization is still ahead for ISA100.11a, but the summit is in sight for WirelessHart, which became an IEC publicly available specification (PAS) last September.
The WirelessHart Communication standard builds on established international standards, including the Hart Protocol (IEC 61158), EDDL (IEC 61804-3), the Institute of Electrical and Electronics Engineers’ IEEE 802.15.4 radio and frequency hopping, spread spectrum and mesh networking technologies. (Much of the same applies to ISA100.11a, by the way, but in a much different mix and with diverging details.)
“The PAS designation is good for three years,” points out Marty Zielinsky, director of technology for Hart and Fieldbus, Emerson Process Management, an automation vendor based in Austin, Texas. “Meanwhile, WirelessHart has moved into the working group stage at IEC, and we’re expecting a full committee draft standard for vote before long.”
The move to PAS status was rapid, Zielinksy says, because for many years, the IEC has recognized that consortiums developing standards such as a WirelessHart are generally “pretty good at building specs that are widely adopted.” An IEC publicly available specification is just that—a specification with enough good points to be usable, at least for the immediate future.
Meanwhile, in May of this year, the Hart Communication Foundation released an update to the Hart test system, an important stepping stone toward the issuance of officially registered products. (A number of products that are engineered to meet the WirelessHart specifications are moving into the marketplace, but the Hart Communication Foundation is yet to announce any that have achieved official registration.) The update adds a set of testing tools that help ensure interoperability of both wired and wireless devices that conform to Hart specifications.
In practice, the Hart test system is a tool that vendors use to evaluate the conformance of new products to Hart specifications. With the addition of the wireless testing layer, the tools now include automated testing of the application layer, token passing data link layer, and time division multiple access (TDMA) data link layer, as well as analysis software for the verification of a device’s conformance to the Hart Protocol specification.
“The test suite allows vendors to engineer and review new products thoroughly prior to submission to Hart for formal approval,” Zielinksy explains. “It greatly streamlines the process by allowing us to work out most of the kinks long before anything goes to Hart for official evaluation.” He adds: “The fact that there are a number of companies announcing products for WirelessHart is helping the drive to make it a full-blown IEC standard.”
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