Have HMI, Will Travel

PDAs—personal digital assistants—you see them almost everywhere these days. And their increased application in the automation and controls environment is no exception. Use of PDAs as human-machine interfaces (HMIs) is growing remarkably, and the market is expected to explode over the next few years.

By Jeanine Katzel March 1, 2004


Abundant connectivity, functional options

Add value to automation investment

Extend control room functions

Power in the field

Sidebars: Connectivity options From manual control to precision automation

PDAs—personal digital assistants—you see them almost everywhere these days. And their increased application in the automation and controls environment is no exception. Use of PDAs as human-machine interfaces (HMIs) is growing remarkably, and the market is expected to explode over the next few years.

Today’s PDAs are powerful, multi-purpose devices. Although they are certainly not a replacement for hard-wired, desktop systems, there is little they cannot be configured to do. They offer rich graphics and ample functionality. In addition, control and automation software is available for almost every application imaginable, giving the engineering staff the capability to react fast to issues on the plant floor, wherever they might be. HMI software is no exception. Most every HMI system available can accommodate the incremental addition of PDAs.As portability has become desirable in process and automation, PDAs have, in turn, brought that portability to the control room.

Taking the show on the road

Harnessing the benefits of PDAs as HMIs requires consideration of options in three primary areas: hardware, software, and services/support.

Hardware, connectivity. Two primary types of handheld devices are used as HMIs in the industrial automation and controls environment: those that use a Microsoft Windows operating system (such as the PocketPC) and Palm, which uses its own proprietary operating system. Both offer similar graphics capabilities, memory, speed, and execution benefits. An abundance of applications is available for each. Obviously, what runs on one device won’t run on the other. Although some software developers offer versions of a software package for each, most concentrate on one type or the other.

Eric Reffett, LabView product manager at National Instruments, says, “Historically, people used Palm PDAs for everyday tasks, such as calendars and address books, while they used PocketPC PDAs with more [Microsoft] Windows-based applications like Word, Excel, Outlook, and Internet Explorer because these PDAs had faster processors. However, today, there are a wide range of available Palm and PocketPC devices, including simple and inexpensive PDAs with little memory and slower processors, as well as powerful and expensive PDAs with faster processors, more memory, and built in features like WiFi and Bluetooth connectivity.” NI’s LabVIEW tools also can help users develop and compile their own HMI applications for handhelds.

What can a user expect from a PDA configured as an HMI? Obviously, they don’t do everything a desktop does, observes Russ Agrusa, president of Iconics. “You can’t put a lot of real estate on a 240 x 340 pixel resolution screen,” admits Agrusa, but their success is apparent. “Today, more than 30 manufacturers make PDAs.”

Iconics Pocket Genesis brings the company’s Genesis32 system to any handheld device. Users can access live HMI displays, alarms, trend information. Mobile technology, such as Iconics’ BizViz Suite, provides access to data through Pocket Genesis using a cellular network.

An important caveat to remember is that powerful handheld hardware loses its power unless it is equipped to communicate with other devices and systems. Access to information doesn’t occur magically. Choice of data transmission method depends on a variety of factors. “The whole area of wireless can be confusing to many people,” cautions Agrusa. “Using a cellular mobile wireless infrastructure is different from an in-plant wireless application using IEEE 802.11.” (See “Connectivity Options” sidebar.)

Software. Applications that bring HMIs to PDAs fall into two areas: 1) software that actually runs on the PDA; 2) functions that essentially load a terminal client on the PDA and use it as a remote viewer. A terminal client configuration lets a user view what is running on the server from the PDA. The application runs remotely, as opposed to a dedicated, wireless application that functions as a stand-alone system running directly on the PDA. Both approaches are valid and abundant, though each has different capabilities.

A variety of factors affect the selection of HMI software. Effective applications on PDAs should extend the control system, allowing you to reach where you couldn’t before, observes Scott Hillman, manager, Advanced Real Time Applications, Honeywell Process Solutions. “We’re just scratching the surface of how these devices are used in process applications,” he says.

Honeywell’s handheld PDA solutions fall under the Mobile PKS umbrella and include IntelaTrac PKS and Mobile Station PKS. Both integrate with the company’s Experion control system to relay critical information, process graphics, digital video, and other key functions using wireless handheld computing devices.

Roy Kok, director of HMI/SCADA product marketing for GE Fanuc agrees with Hillman. “PDAs have grown significantly in popularity over the past four years or so. One important function of the PDA is the ability to ease data collection. The HMI allows me to see what’s going on. I wouldn’t necessarily control my entire plant through a PDA device, but I would use it to analyze and better react to conditions,” says Kok. GE Fanuc’s PalmView, TabletView, and LogicDeveloper PDA handheld devices work with its industrial automation software to give mobile users access to real-time data of plant control systems.

Service and support. A system requires consideration of elements beyond hardware and software, including:

Security, reliability. Wireless aspects of PDAs often raise legitimate concerns in the minds of many users; however, measures exist today to make any wireless environment reasonably secure. Wireless range restrictions create some security by limiting data availability. Also, most industrial operations have been or are being secured by the IT department.

Robustness. Will PDAs work sufficiently? Are they reliable? Can they perform the functions needed to make them useful? These application-specific questions should be answered before a system is put in place.

Signal coverage. Is adequate signal coverage available? An installation might populate the entire plant with access points, but to assume 100% coverage is unrealistic—and probably unnecessary. Are there areas where signal outages may occur? How will those be managed?

Human factors. There is also a need to look at the human factors limiting use of PDAs as HMIs as much as the technology ones, emphasizes Ramal Murali, president, Software Horizons Inc. “No human can differentiate among more than five to seven things. Putting more pieces of information than that on any screen is just too much. You can get a lot of power in a PDA, but it still doesn’t have the capacity of a desktop system,” he says.

Software Horizons’ InstantHMI converts a handheld device into an HMI that runs on Palm OS and Microsoft Windows-based platforms. Its design once, deploy anywhere development technology enables an application to be created one time, then deployed on any of numerous target platforms. The system is compatible with almost any major manufacturer’s controllers, including Rockwell Automation; Watlow; and Wago.

Technology no barrier

Technological advancements have eliminated most any barrier to using PDAs as HMIs. Limitations impact such functions as data processing capacity and graphics resolution. However, extending the control system into the field today is not just possible, it’s necessary.

“It really comes down to deciding what it is you want to accomplish,” says GE Fanuc’s Kok. “The technology exists to do it but, you want to implement only what will add value. What helps you better run your plant? Technology exists to get that data to you in real time. Accurately define your needs, then decide what will provide the best return.”

“Make sure your handheld devices integrate smoothly into your existing system,” warns Honeywell’s Hillman. The goal should be to incorporate the field operator and maintenance operator into the automation environment as much in real time as is practical. “We want to unify that space, integrating what goes on in the control room with what goes on in the field,” he says. “Handheld computing power should add value to control systems—to the automation investment the company has already made.”

Connectivity options

Connectivity options depend in large part on the application. Although the four summarized here are probably most common, don’t rule out other transmission methods. Other standards in the works (Zigbee, at

Among the most common is infrared technology . An inexpensive transmission method, it also has some serious restrictions. Because IR can be affected by brightness and dust, it’s less reliable. However, it finds good application in clean rooms, for example, where little interference is likely. Today’s Microsoft Windows operating systems automatically detect IR ports, which are easily attached to devices to build a viable, if somewhat less stable environment. IR connectivity gives devices the ability to communicate in the 4 to 10 ft range.

Although competition admittedly exists between IEEE 802.11 standards ( Bluetooth (National Instruments’ Eric Reffett, LabVIEW product manager at National Instruments, says, “IEEE 802.11 is widely available and easy to obtain components for. It’s Ethernet, so it’s easy to set up, understand, and adapt. Many PDAs have 802.11 built into them. Bluetooth also has specific benefits, but requires a bigger learning curve. It has a recognition system built into its protocol. When two Bluetooth devices are in proximity to one other, they automatically start communicating and find out if they can share data. Such action does not happen with 802.11 devices. Communication must be established with each device manually. A number of industries—for example, automotive—are beginning to discover these advantages.”

When it comes to the need for long-distance, global transmission, use of cellular technology provides reliable, virtually limitless communication (see “From manual control to precision automation” sidebar for real world application example).

From manual control to precision automation

Water is a precious commodity in the Western U.S.; its use is carefully controlled in many communities. Among the carefully guarded resources is Colorado’s South Platte River. In a project sponsored by a consortium of county and municipal governments, an irrigation canal was constructed to conserve water use by readjusting flow through the canal daily, according to the volume of water expected to come down the South Platte.

Initially, the system, known as the Fulton Ditch Project, was controlled manually. Although results were satisfactory, the manual process was not. Operators doing work on the canal were often 30 to 50 miles away when called upon to initiate a flow change. Without a way to modify the flow remotely, changes were time-consuming and inefficient.

To make the system more responsive, the operation was automated last year. Now an operator pulls out his PDA, pushes the “connect” button on the cell phone function of the device, and links to the Opto 22 Snap Ultimate I/O system controlling the head gate. All connections are security/password protected over the Modbus TCP/IP network.

Operators interact with the system through an HMI control application built by Performance Software Associates, running under the Microsoft CE operating system on PocketPCs. From the PDA control screen, the operator can see the position of the gates and can select or modify flow rate. Within 15 minutes of receiving notification of a change, the Ultimate I/O controller adjusts the gates to establish a flow rate within one cubic foot per second of the requested rate.

Operators can do everything from a PDA that they can do at the head gate itself. Adjustments are possible from any location where a cellular phone works. The system delivers reliable, accurate water flows to customers day or night. Data are available in real time; updates occur once a second.

Commenting on the system, Joe Berger, president of Performance Software Associates says, “The biggest benefit has been the reliable delivery of water to users. Previously, the gates needed to be readjusted manually two or three times a day.

“We were very impressed at how responsive and how well this HMI implementation actually worked,” he continues. “We did it because the customer needed another way to control his operation. We proposed it with some trepidation, but frankly—with the development tools that are available for CE and the simulation available—once we had it all in place, we put it on that little PDA and it just ran like gangbusters.”

For more information on Performance Software Associates, visit