By Rich Merritt, Senior Technical EditorHOW DO YOU
take yours? Straight up with a twist or with syrup and berries? As we've reported frequently in this magazine, industrial Ethernet and wireless technologies are all the rage. Virtually every new product now comes with an Ethernet port, and enough wireless attachments are available to make any control or instrumentation product a wireless device. It would seem we are heading for a wireless, Ethernet world.
But don’t count out other technologies just yet. Established fieldbuses are making giant strides; one of the oldest networks of all—Modbus—is gaining new life; and not everybody is sold on the newest technologies. TALES FROM THE EDGE
As trends emerge more clearly, we usually can find a few early adopters to help define accompanying benefits. Ian Drazin is electrical and instrumentation supervisor at Potlach Corp.
, which produces coated printing papers, bleached paperboard and private-label tissue products in North Las Vegas, Nev. Drazin says Potlach went wireless four years ago in its warehouse and production area, primarily to control fork trucks, but he couldn’t leave well enough alone.
“I began redesigning our DH+ and Ethernet networks, connecting them to a field-mounted Allen-Bradley gateway,” says Drazin. “Once complete, I connected the company LAN to the gateway. Now, from my office, I can route communications through the gateway and gain access to my PLC processors. To make it better, I then coerced my IT department to install 802.11b wireless PCMCIA cards in our maintenance laptops. Armed with such a tool, I could connect to the PLC via my laptop’s wireless connection and walk up to the equipment I was working on and see input/outputs in real time.”
Drazin enjoys many benefits from this system, including wireless Internet access. “Many equipment manufacturers finally are making comprehensive product information available on their websites,” he notes. “Maintenance personnel save time if they have immediate access to product drawings, specifications, user manuals, set-up procedures, etc.”
Joe Markham, control engineer at biopharmaceutical manufacturer Protein Design Labs
, Brooklyn Park, Minn., uses industrial Ethernet in his process development group. “We have a number of PLCs, operator interfaces and PCs connected via Ethernet,” he reports. “Ethernet is fast, especially compared to going via serial port out to a KF2 box, and onto DH+. Also, with Ethernet we can leverage the business infrastructure. We have our switches configured, so only selected engineering people can access the control system Ethernet LAN via the business LAN. This lets the engineers connect to the control system components from anywhere, while keeping the LANs isolated.”
“The downsides to wireless networks are security, dead spots, unexplained loss of connection and slower data transfer…but wireless works surprisingly well. even in high RF industrial manufacturing environments.”
Engineers with laptops especially benefit. “Laptops all come with Ethernet these days, but none of them come with DH+, Profibus, or any other control LAN technology,” he notes. While Drazin enjoys the benefits of wireless, he won’t use it for control. “The downsides to wireless networks are security, dead spots, unexplained loss of connection and slower data transfer,” he laments. However, he’ll continue to use it for the purposes noted above. “Personally, the benefits are so great that I’m willing to put up with the negatives. I also want to mention that wireless technology works surprisingly well even in high RF industrial manufacturing environments.”
But that’s the limit for him, adds Drazin. “I haven’t installed, nor do I plan to install, wireless instrumentation,” he states. “Believe me, I have thought about it. The current technology is just not there yet. I relate 802.11b/g to Windows 95. It works but it is unstable and quirky. Perhaps 802.11z will be the ticket.”
Markham also has tried wireless. “At a previous job, we used wireless data terminals extensively,” he says. “These were basically wireless VT100 terminals with a barcode scanner built in. They interfaced with a custom inventory control app. Very nice for the warehouse people. The only downside was the several thousand-dollar-per-terminal cost for units certified for use in flammable environments, and the fact that they had an average lifetime of about 12 months.”
While Markham is willing to try wireless again, he has some reservations. “I don't want anything that's just been introduced,” he says. “At that point, nobody knows all the interoperability tricks. The vendor's support people might not even have heard of it yet, firmware problems are notoriously difficult to track down, and promised software updates nearly always ship late—sometimes years late.”
A paper mill in Canada recently installed a process control system on a new paper machine. “We wanted to use proven technology,” says plant manager [[NAME???]], “so we didn’t want to use wireless or Internet technologies for control.” His paper machine uses seven different networks, including Ethernet/IP, Foundation fieldbus, Profibus, DeviceNet, ControlNet, Bailey Ring and HART.
The integration of these networks seems to have gone off without a hitch. “We invited the vendors of eight major systems representing five different countries to a customer acceptance test,” he says. “We used OPC to connect the PC-based systems and RS-485 to connect the PLC systems.”