In the on-going wireless standards wars, Bob Karschnia, global vp for wireless at Emerson, totally rebutted the battery life challenge raised by members of the ISA100.11a. "Emerson WirelessHART battery-powered sensors have been in the field for around eight years. In that time there have been no requests from our customers for Emerson to make replacement battery packs available, and we have not needed to supply any."
Karschnia went on to explain, "Monitoring applications in general have not needed a high data rate/short response time, and the sensor developments over recent years have focused on reducing the actual power requirement from the sensor circuitry, which reduces the power drain." Several alternative solutions to standard batteries are the subject of R+D projects, using various energy harvesting techniques, but even with the currently available battery technology Karschnia anticipates a typical monitoring battery life of around ten years.
One of the major functions of the intelligent wireless gateway is to provide power management for the entire mesh network, including the sensors, and this avoids imposing a high power demand by overloading the sensor wireless communications, even on those closest to the gateway.
In response to the comments, Karschnia commented, "This is just an attempt to deflect attention from the lack of acceptance of ISA100.11a by the marketplace, while IEC62591 (WirelessHART) continues to march forward at an ever accelerating pace." He suggested that this is due to the fact that ISA100.11a is not a full automation standard like IEC 62591―and that this will severely limit any true vendor interoperability within ISA100.
Extending Wireless Capabilities
Another criticism that was evident from comments made at the June 2010 Yokogawa launch of its ISA100.11a sensors, was that the IEC62591 WirelessHART standard related solely to the field sensors in a network, whereas the ISA100 family of standards would eventually relate to the many different requirements for wireless networks, encompassing Wi-Fi, video, worker communications and location. Karschnia points out that the Emerson wireless access points are an example of its co-operation with Cisco, the acknowledged experts in IT networking and communications technology and services. These wireless mesh access points are based on the Cisco Aironet 1520 Series and support dual-band radios compliant with IEEE 802.11a and 802.11b/g standards, as driven by the IT community, providing a universal standard network infrastructure for easy integration of all the wireless applications in the plant, including security, personnel and asset tracking, and mobile worker productivity solutions.
A validation of the combination of this expertise has recently been reported in a joint paper by Karschnia and Greg LaFramboise of Chevron in Richmond, Calif., where a wireless infrastructure was installed, blanketing 80% of a Chevron U.S. refinery, to provide an "add-at-will" wireless automation capability.
Further questioning of Bob Karschnia by the European press elicited the comments that Merck has carried out testing of wireless sensors in relation to operating in pharmaceutical manufacturing and has determined that the FDA regulatory requirements can be satisfied.
Karschnia pointed out that Emerson currently offers 14 wireless sensor product families (plus the THUM WirelessHART adaptor), but that seven more product ranges will be available with wireless interfaces in 2011, right across the Emerson portfolio.