Panel Meters Take Control

Panel Meters Now Can Do Control in the Process, and so Many Users Don't Need All the PLCs and SCADA Software They Had to Use in the Past

Jim MontagueBy Jim Montague, Executive Editor

Basic panel meters have been adding features for years, but lately it seems they're on more of a tear than usual. Many have new display options, but some add functions that put them squarely in territory occupied by formerly disparate devices such as data acquisition systems and programmable controllers.

"The driving force now is the global market and especially international users, who don't want to deal with multiple types of meters," says Jeff Thornton, indication product manager at Red Lion Controls (www.redlion.net). "They want to stick with one panel meter, and pack as many functions into it as possible."

Red Lion introduced its Pax2 Series analog panel meters at the end of last year, and just recently added a digital version. The company has a two-line, tri-colored display, but takes it further with a six-digit top line and a nine-digit bottom line. "We have one customer, an OEM and reseller in Detroit, who says he's been able to replace 24 different meters with one Pax2 and three option cards," Thornton says.

Option cards fit into three slots on the Pax2—two-relay, four-relay or four-position synchronized—which allows cards to be switched in the field at any time. This lets users handle different process set points, retransmitted signals and various communication protocols such as RS-232, RS-485, Modbus, DeviceNet and Profibus. "Many HMIs can handle process data, but not directly from sensors," Thornton explains. "Pax2 can accept this input from local signal conditioners."

Moving even closer to programmable and distributed controller territory, Pax2 also has a built-in USB programming port to collect data or download instructions to the panel meter, which it can relay to production-level devices.

Panel meters have been getting smaller and more electronically powerful for many years, and so it's natural for them to employ networking to reach out to other applications and systems, says Steve Hollander, general manager of Newport Electronics (www.newportus.com). "The big thing for us—that's also unique to us—is that our panel meters have embedded Internet web servers via local Ethernet TCP/IP," he says.

Not content to stop where wired Ethernet connectivity ends, Newport also recently launched its WiSeries panel meters, which use IEEE 802.15.4 or ZigBee to accept signals from up to eight wireless transmitters. "It's a lot like a scanner that can display results, but it also can serve as a controller," Hollander says. "Panel meters and controllers have converged lately because the meters have the PID firmware needed to do control."

Panel meters are branching out because their new control-related features let them trespass on and fill some new technical niches, adds Joseph Ryan, electrical engineer at Precision Digital (www.predig.com). "People don't want just local displays, and are demanding added data-processing capabilities so their panel meters can be used as backup control systems or replacement batch controllers, and so they don't have to buy another PLC," he says. "Many users aren't able to program PLCs, but they can program a panel meter and use a menu structure they already know to also do control functions."

To meet these needs, Precision Digital introduced its ProVu dual-input panel meter, and a ProVu batch controller. "These panel meters don't have an operating system like a PC, but the microprocessor chips inside, such as our ARM Series, are still so powerful that complex code can be written for them," Ryan explains. "So, over the past 10 years, we developed firmware for our meters, and programmed them in C code, so they can perform all the tasks users might need. Now we have a panel meter that can do control, but the operations guy doesn't have to be scared of it because he can still program it using the same four-button panel."

Options enable users to connect ProVu directly to a PC to configure and monitor the meter, do data logging, and archive back to the PC to meet regulatory documentation requirements. "Panel meters now can do control in the process, and so many users don't need all the PLCs and SCADA software they had to use in the past," Ryan says. "In the future, I think we'll see them tie into smart mobile devices, too."

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